/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.pulsar.client.impl;

import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkState;
import static com.scurrilous.circe.checksum.Crc32cIntChecksum.computeChecksum;
import static com.scurrilous.circe.checksum.Crc32cIntChecksum.resumeChecksum;
import static java.lang.String.format;
import static org.apache.pulsar.client.impl.MessageImpl.SchemaState.Broken;
import static org.apache.pulsar.client.impl.MessageImpl.SchemaState.None;
import static org.apache.pulsar.client.impl.ProducerBase.MultiSchemaMode.Auto;
import static org.apache.pulsar.client.impl.ProducerBase.MultiSchemaMode.Enabled;
import static org.apache.pulsar.common.protocol.Commands.hasChecksum;
import static org.apache.pulsar.common.protocol.Commands.readChecksum;
import static org.apache.pulsar.common.util.Runnables.catchingAndLoggingThrowables;
import com.google.common.annotations.VisibleForTesting;
import io.netty.buffer.ByteBuf;
import io.netty.channel.Channel;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelOutboundHandler;
import io.netty.channel.ChannelPromise;
import io.netty.util.AbstractReferenceCounted;
import io.netty.util.Recycler;
import io.netty.util.Recycler.Handle;
import io.netty.util.ReferenceCountUtil;
import io.netty.util.ReferenceCounted;
import io.netty.util.Timeout;
import io.netty.util.TimerTask;
import io.netty.util.concurrent.ScheduledFuture;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Optional;
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.concurrent.Semaphore;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.atomic.AtomicIntegerFieldUpdater;
import java.util.concurrent.atomic.AtomicLongFieldUpdater;
import java.util.function.Consumer;
import org.apache.commons.lang3.StringUtils;
import org.apache.pulsar.client.api.BatcherBuilder;
import org.apache.pulsar.client.api.CompressionType;
import org.apache.pulsar.client.api.Message;
import org.apache.pulsar.client.api.MessageCrypto;
import org.apache.pulsar.client.api.MessageId;
import org.apache.pulsar.client.api.Producer;
import org.apache.pulsar.client.api.ProducerAccessMode;
import org.apache.pulsar.client.api.ProducerCryptoFailureAction;
import org.apache.pulsar.client.api.PulsarClientException;
import org.apache.pulsar.client.api.PulsarClientException.CryptoException;
import org.apache.pulsar.client.api.PulsarClientException.IncompatibleSchemaException;
import org.apache.pulsar.client.api.PulsarClientException.TimeoutException;
import org.apache.pulsar.client.api.Schema;
import org.apache.pulsar.client.api.transaction.Transaction;
import org.apache.pulsar.client.impl.conf.ProducerConfigurationData;
import org.apache.pulsar.client.impl.crypto.MessageCryptoBc;
import org.apache.pulsar.client.impl.schema.JSONSchema;
import org.apache.pulsar.client.impl.schema.SchemaUtils;
import org.apache.pulsar.client.impl.transaction.TransactionImpl;
import org.apache.pulsar.client.util.MathUtils;
import org.apache.pulsar.common.allocator.PulsarByteBufAllocator;
import org.apache.pulsar.common.api.proto.MessageMetadata;
import org.apache.pulsar.common.api.proto.ProtocolVersion;
import org.apache.pulsar.common.compression.CompressionCodec;
import org.apache.pulsar.common.compression.CompressionCodecProvider;
import org.apache.pulsar.common.naming.TopicName;
import org.apache.pulsar.common.protocol.ByteBufPair;
import org.apache.pulsar.common.protocol.Commands;
import org.apache.pulsar.common.protocol.Commands.ChecksumType;
import org.apache.pulsar.common.protocol.schema.SchemaHash;
import org.apache.pulsar.common.protocol.schema.SchemaVersion;
import org.apache.pulsar.common.schema.SchemaInfo;
import org.apache.pulsar.common.schema.SchemaType;
import org.apache.pulsar.common.util.BackoffBuilder;
import org.apache.pulsar.common.util.DateFormatter;
import org.apache.pulsar.common.util.FutureUtil;
import org.apache.pulsar.common.util.RelativeTimeUtil;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class ProducerImpl<T> extends ProducerBase<T> implements TimerTask, ConnectionHandler.Connection {

    // Producer id, used to identify a producer within a single connection
    protected final long producerId;

    // Variable is updated in a synchronized block
    private volatile long msgIdGenerator;

    protected final OpSendMsgQueue pendingMessages;
    private final Optional<Semaphore> semaphore;
    private volatile Timeout sendTimeout = null;
    private final long lookupDeadline;
    private int chunkMaxMessageSize;

    @SuppressWarnings("rawtypes")
    private static final AtomicLongFieldUpdater<ProducerImpl> PRODUCER_DEADLINE_UPDATER = AtomicLongFieldUpdater
            .newUpdater(ProducerImpl.class, "producerDeadline");
    @SuppressWarnings("unused")
    private volatile long producerDeadline = 0; // gets set on first successful connection

    private final BatchMessageContainerBase batchMessageContainer;
    private CompletableFuture<MessageId> lastSendFuture = CompletableFuture.completedFuture(null);
    private LastSendFutureWrapper lastSendFutureWrapper = LastSendFutureWrapper.create(lastSendFuture);

    // Globally unique producer name
    protected String producerName;
    private final boolean userProvidedProducerName;

    private String connectionId;
    private String connectedSince;
    protected final int partitionIndex;

    private final ProducerStatsRecorder stats;

    private final CompressionCodec compressor;

    static final AtomicLongFieldUpdater<ProducerImpl> LAST_SEQ_ID_PUBLISHED_UPDATER = AtomicLongFieldUpdater
            .newUpdater(ProducerImpl.class, "lastSequenceIdPublished");
    private volatile long lastSequenceIdPublished;

    static final AtomicLongFieldUpdater<ProducerImpl> LAST_SEQ_ID_PUSHED_UPDATER = AtomicLongFieldUpdater
            .newUpdater(ProducerImpl.class, "lastSequenceIdPushed");
    protected volatile long lastSequenceIdPushed;
    private volatile boolean isLastSequenceIdPotentialDuplicated;

    private final MessageCrypto msgCrypto;

    private ScheduledFuture<?> keyGeneratorTask = null;

    private final Map<String, String> metadata;

    private Optional<byte[]> schemaVersion = Optional.empty();

    private final ConnectionHandler connectionHandler;

    // A batch flush task is scheduled when one of the following is true:
    // - A message is added to a message batch without also triggering a flush for that batch.
    // - A batch flush task executes with messages in the batchMessageContainer, thus actually triggering messages.
    // - A message was sent more recently than the configured BatchingMaxPublishDelayMicros. In this case, the task is
    //   scheduled to run BatchingMaxPublishDelayMicros after the most recent send time.
    // The goal is to optimize batch density while also ensuring that a producer never waits longer than the configured
    // batchingMaxPublishDelayMicros to send a batch.
    // Only update from within synchronized block on this producer.
    private ScheduledFuture<?> batchFlushTask;
    // The time, in nanos, of the last batch send. This field ensures that we don't deliver batches via the
    // batchFlushTask before the batchingMaxPublishDelayMicros duration has passed.
    private long lastBatchSendNanoTime;

    private Optional<Long> topicEpoch = Optional.empty();
    private final List<Throwable> previousExceptions = new CopyOnWriteArrayList<Throwable>();

    private boolean errorState;

    private final boolean pauseSendingToPreservePublishOrderOnSchemaRegFailure;
    // This variable can be exposed as a metrics in the future, a PIP is needed.
    private final AtomicInteger pendingQueueFullCounter;

    public ProducerImpl(PulsarClientImpl client, String topic, ProducerConfigurationData conf,
                        CompletableFuture<Producer<T>> producerCreatedFuture, int partitionIndex, Schema<T> schema,
                        ProducerInterceptors interceptors, Optional<String> overrideProducerName) {
        super(client, topic, conf, producerCreatedFuture, schema, interceptors);
        this.producerId = client.newProducerId();
        this.producerName = conf.getProducerName();
        this.userProvidedProducerName = StringUtils.isNotBlank(producerName);
        this.partitionIndex = partitionIndex;
        this.pendingMessages = createPendingMessagesQueue();
        // Replication needs to be paused when a message can not be replicated due to failed schema registration.
        // Otherwise, it may cause an out-of-order issue, and it may lead to a messages lost issue if users enabled
        // deduplication on the remote side.
        this.pauseSendingToPreservePublishOrderOnSchemaRegFailure = conf.isReplProducer();
        if (conf.getMaxPendingMessages() > 0) {
            this.semaphore = Optional.of(new Semaphore(conf.getMaxPendingMessages(), true));
        } else {
            this.semaphore = Optional.empty();
        }
        overrideProducerName.ifPresent(key -> this.producerName = key);

        this.compressor = CompressionCodecProvider.getCompressionCodec(conf.getCompressionType());

        if (conf.getInitialSequenceId() != null) {
            long initialSequenceId = conf.getInitialSequenceId();
            this.lastSequenceIdPublished = initialSequenceId;
            this.lastSequenceIdPushed = initialSequenceId;
            this.msgIdGenerator = initialSequenceId + 1L;
        } else {
            this.lastSequenceIdPublished = -1L;
            this.lastSequenceIdPushed = -1L;
            this.msgIdGenerator = 0L;
        }

        if (conf.isEncryptionEnabled()) {
            String logCtx = "[" + topic + "] [" + producerName + "] [" + producerId + "]";

            if (conf.getMessageCrypto() != null) {
                this.msgCrypto = conf.getMessageCrypto();
            } else {
                // default to use MessageCryptoBc;
                MessageCrypto msgCryptoBc;
                try {
                    msgCryptoBc = new MessageCryptoBc(logCtx, true);
                } catch (Exception e) {
                    log.error("MessageCryptoBc may not included in the jar in Producer. e:", e);
                    msgCryptoBc = null;
                }
                this.msgCrypto = msgCryptoBc;
            }
        } else {
            this.msgCrypto = null;
        }

        if (this.msgCrypto != null) {
            // Regenerate data key cipher at fixed interval
            keyGeneratorTask = client.eventLoopGroup().scheduleWithFixedDelay(catchingAndLoggingThrowables(() -> {
                try {
                    msgCrypto.addPublicKeyCipher(conf.getEncryptionKeys(), conf.getCryptoKeyReader());
                } catch (CryptoException e) {
                    if (!producerCreatedFuture.isDone()) {
                        log.warn("[{}] [{}] [{}] Failed to add public key cipher.", topic, producerName, producerId);
                        producerCreatedFuture.completeExceptionally(
                                PulsarClientException.wrap(e,
                                        String.format("The producer %s of the topic %s "
                                                        + "adds the public key cipher was failed",
                                                producerName, topic)));
                    }
                }
            }), 0L, 4L, TimeUnit.HOURS);
        }

        if (conf.getSendTimeoutMs() > 0) {
            sendTimeout = client.timer().newTimeout(this, conf.getSendTimeoutMs(), TimeUnit.MILLISECONDS);
        }

        this.lookupDeadline = System.currentTimeMillis() + client.getConfiguration().getLookupTimeoutMs();
        if (conf.isBatchingEnabled()) {
            BatcherBuilder containerBuilder = conf.getBatcherBuilder();
            if (containerBuilder == null) {
                containerBuilder = BatcherBuilder.DEFAULT;
            }
            this.batchMessageContainer = (BatchMessageContainerBase) containerBuilder.build();
            this.batchMessageContainer.setProducer(this);
        } else {
            this.batchMessageContainer = null;
        }
        if (client.getConfiguration().getStatsIntervalSeconds() > 0) {
            stats = new ProducerStatsRecorderImpl(client, conf, this);
        } else {
            stats = ProducerStatsDisabled.INSTANCE;
        }

        if (conf.getProperties().isEmpty()) {
            metadata = Collections.emptyMap();
        } else {
            metadata = Collections.unmodifiableMap(new HashMap<>(conf.getProperties()));
        }

        pendingQueueFullCounter = new AtomicInteger();
        this.connectionHandler = initConnectionHandler();
        setChunkMaxMessageSize();
        grabCnx();
    }

    @VisibleForTesting
    public int getPendingQueueFullCount() {
        return pendingQueueFullCounter.get();
    }

    ConnectionHandler initConnectionHandler() {
        return new ConnectionHandler(this,
            new BackoffBuilder()
                .setInitialTime(client.getConfiguration().getInitialBackoffIntervalNanos(), TimeUnit.NANOSECONDS)
                .setMax(client.getConfiguration().getMaxBackoffIntervalNanos(), TimeUnit.NANOSECONDS)
                .setMandatoryStop(Math.max(100, conf.getSendTimeoutMs() - 100), TimeUnit.MILLISECONDS)
                .create(),
        this);
    }

    private void setChunkMaxMessageSize() {
        this.chunkMaxMessageSize = conf.getChunkMaxMessageSize() > 0
                ? Math.min(conf.getChunkMaxMessageSize(), getMaxMessageSize())
                : getMaxMessageSize();
    }

    protected void semaphoreRelease(final int releaseCountRequest) {
        if (semaphore.isPresent()) {
            if (!errorState) {
                final int availableReleasePermits =
                        conf.getMaxPendingMessages() - this.semaphore.get().availablePermits();
                if (availableReleasePermits - releaseCountRequest < 0) {
                    log.error("Semaphore permit release count request greater then availableReleasePermits"
                                    + " : availableReleasePermits={}, releaseCountRequest={}",
                            availableReleasePermits, releaseCountRequest);
                    errorState = true;
                }
            }
            semaphore.get().release(releaseCountRequest);
        }
    }

    protected OpSendMsgQueue createPendingMessagesQueue() {
        return new OpSendMsgQueue();
    }

    public ConnectionHandler getConnectionHandler() {
        return connectionHandler;
    }

    public boolean isBatchMessagingEnabled() {
        return conf.isBatchingEnabled();
    }

    private boolean isMultiSchemaEnabled(boolean autoEnable) {
        if (multiSchemaMode != Auto) {
            return multiSchemaMode == Enabled;
        }
        if (autoEnable) {
            multiSchemaMode = Enabled;
            return true;
        }
        return false;
    }

    @Override
    public long getLastSequenceId() {
        return lastSequenceIdPublished;
    }

    @Override
    CompletableFuture<MessageId> internalSendAsync(Message<?> message) {
        CompletableFuture<MessageId> future = new CompletableFuture<>();

        MessageImpl<?> interceptorMessage = (MessageImpl) beforeSend(message);
        // Retain the buffer used by interceptors callback to get message. Buffer will release after complete
        // interceptors.
        interceptorMessage.getDataBuffer().retain();
        if (interceptors != null) {
            interceptorMessage.getProperties();
        }

        int msgSize = interceptorMessage.getDataBuffer().readableBytes();
        sendAsync(interceptorMessage, new DefaultSendMessageCallback(future, interceptorMessage, msgSize));
        return future;
    }

    public void printWarnLogWhenCanNotDetermineDeduplication(Channel channel, long sequenceId,
                                                             long highestSequenceId) {
        log.warn("[{}] producer [id:{}, name:{}, channel: {}] message with sequence-id {}-{} published by has been"
                        + " dropped because Broker can not determine whether is duplicate or not",
                topic, producerId, producerName, channel, sequenceId, highestSequenceId);
    }

    private class DefaultSendMessageCallback implements SendCallback {

        CompletableFuture<MessageId> sendFuture;
        MessageImpl<?> currentMsg;
        long createdAt = System.nanoTime();
        SendCallback nextCallback = null;
        MessageImpl<?> nextMsg = null;

        DefaultSendMessageCallback(CompletableFuture<MessageId> sendFuture, MessageImpl<?> currentMsg, int msgSize) {
            this.sendFuture = sendFuture;
            this.currentMsg = currentMsg;
        }

        @Override
        public CompletableFuture<MessageId> getFuture() {
            return sendFuture;
        }

        @Override
        public SendCallback getNextSendCallback() {
            return nextCallback;
        }

        @Override
        public MessageImpl<?> getNextMessage() {
            return nextMsg;
        }

        @Override
        public void sendComplete(Exception e) {
            SendCallback loopingCallback = this;
            MessageImpl<?> loopingMsg = currentMsg;
            while (loopingCallback != null) {
                onSendComplete(e, loopingCallback, loopingMsg);
                loopingMsg = loopingCallback.getNextMessage();
                loopingCallback = loopingCallback.getNextSendCallback();
            }
        }

        private void onSendComplete(Exception e, SendCallback sendCallback, MessageImpl<?> msg) {
            long createdAt = (sendCallback instanceof ProducerImpl.DefaultSendMessageCallback)
                    ? ((DefaultSendMessageCallback) sendCallback).createdAt : this.createdAt;
            long latencyNanos = System.nanoTime() - createdAt;
            ByteBuf payload = msg.getDataBuffer();
            if (payload == null) {
                log.error("[{}] [{}] Payload is null when calling onSendComplete, which is not expected.",
                        topic, producerName);
            }
            try {
                if (e != null) {
                    stats.incrementSendFailed();
                    onSendAcknowledgement(msg, null, e);
                    sendCallback.getFuture().completeExceptionally(e);
                } else {
                    stats.incrementNumAcksReceived(latencyNanos);
                    onSendAcknowledgement(msg, msg.getMessageId(), null);
                    sendCallback.getFuture().complete(msg.getMessageId());
                }
            } finally {
                ReferenceCountUtil.safeRelease(payload);
            }
        }

        @Override
        public void addCallback(MessageImpl<?> msg, SendCallback scb) {
            nextMsg = msg;
            nextCallback = scb;
        }
    }

    @Override
    CompletableFuture<MessageId> internalSendWithTxnAsync(Message<?> message, Transaction txn) {
        if (txn == null) {
            return internalSendAsync(message);
        } else {
            CompletableFuture<MessageId> completableFuture = new CompletableFuture<>();
            if (!((TransactionImpl) txn).checkIfOpen(completableFuture)) {
               return completableFuture;
            }
            return ((TransactionImpl) txn).registerProducedTopic(topic)
                        .thenCompose(ignored -> internalSendAsync(message));
        }
    }

    /**
     * Compress the payload if compression is configured.
     * @param payload
     * @return a new payload
     */
    private ByteBuf applyCompression(ByteBuf payload) {
        ByteBuf compressedPayload = compressor.encode(payload);
        payload.release();
        return compressedPayload;
    }

    /**
     * Note on ByteBuf Release Behavior.
     *
     * <p>If you have a customized callback, please ignore the note below.</p>
     *
     * <p>When using the default callback, please confirm that the {@code refCnt()} value of the {@code message}
     * (as returned by {@link MessageImpl#getDataBuffer}) is {@code 2} when you call this method. This is because
     * the {@code ByteBuf} will be released twice under the following conditions:</p>
     *
     * <ul>
     *   <li><b>Batch Messaging Enabled:</b>
     *     <ol>
     *       <li>Release 1: When the message is pushed into the batched message queue (see {@link #doBatchSendAndAdd}).
     *       </li>
     *       <li>Release 2: In the method {@link SendCallback#sendComplete(Throwable, OpSendMsgStats)}.</li>
     *     </ol>
     *   </li>
     *   <li><b>Single Message (Batch Messaging Disabled):</b>
     *     <ol>
     *       <li>Release 1: When the message is written out by
     *       {@link ChannelOutboundHandler#write(ChannelHandlerContext, Object, ChannelPromise)}.</li>
     *       <li>Release 2: In the method {@link ByteBufPair#release()}, which was called by
     *       {@link SendCallback#sendComplete(Throwable, OpSendMsgStats)}.</li>
     *     </ol>
     *   </li>
     * </ul>
     */
    public void sendAsync(Message<?> message, SendCallback callback) {
        checkArgument(message instanceof MessageImpl);
        MessageImpl<?> msg = (MessageImpl<?>) message;
        MessageMetadata msgMetadata = msg.getMessageBuilder();
        ByteBuf payload = msg.getDataBuffer();
        final int uncompressedSize = payload.readableBytes();

        if (!isValidProducerState(callback, message.getSequenceId())) {
            payload.release();
            return;
        }

        if (!canEnqueueRequest(callback, message.getSequenceId(), uncompressedSize)) {
            payload.release();
            return;
        }

        // If compression is enabled, we are compressing, otherwise it will simply use the same buffer
        ByteBuf compressedPayload = payload;
        boolean compressed = false;
        // Batch will be compressed when closed
        // If a message has a delayed delivery time, we'll always send it individually
        if (!isBatchMessagingEnabled() || msgMetadata.hasDeliverAtTime()) {
            compressedPayload = applyCompression(payload);
            compressed = true;

            // validate msg-size (For batching this will be check at the batch completion size)
            int compressedSize = compressedPayload.readableBytes();
            if (compressedSize > getMaxMessageSize() && !this.conf.isChunkingEnabled()) {
                compressedPayload.release();
                String compressedStr = conf.getCompressionType() != CompressionType.NONE ? "Compressed" : "";
                PulsarClientException.InvalidMessageException invalidMessageException =
                        new PulsarClientException.InvalidMessageException(
                                format("The producer %s of the topic %s sends a %s message with %d bytes that exceeds"
                                                + " %d bytes",
                        producerName, topic, compressedStr, compressedSize, getMaxMessageSize()));
                completeCallbackAndReleaseSemaphore(uncompressedSize, callback, invalidMessageException);
                return;
            }
        }

        if (!msg.isReplicated() && msgMetadata.hasProducerName()) {
            PulsarClientException.InvalidMessageException invalidMessageException =
                new PulsarClientException.InvalidMessageException(
                    format("The producer %s of the topic %s can not reuse the same message", producerName, topic),
                        msg.getSequenceId());
            completeCallbackAndReleaseSemaphore(uncompressedSize, callback, invalidMessageException);
            compressedPayload.release();
            return;
        }

        if (!populateMessageSchema(msg, callback)) {
            compressedPayload.release();
            return;
        }

        // Update the message metadata before computing the payload chunk size to avoid a large message cannot be split
        // into chunks.
        updateMessageMetadata(msgMetadata, uncompressedSize);

        // send in chunks
        int totalChunks;
        int payloadChunkSize;
        if (canAddToBatch(msg) || !conf.isChunkingEnabled()) {
            totalChunks = 1;
            payloadChunkSize = getMaxMessageSize();
        } else {
            // Reserve current metadata size for chunk size to avoid message size overflow.
            // NOTE: this is not strictly bounded, as metadata will be updated after chunking.
            // So there is a small chance that the final message size is larger than ClientCnx.getMaxMessageSize().
            // But it won't cause produce failure as broker have 10 KB padding space for these cases.
            payloadChunkSize = getMaxMessageSize() - msgMetadata.getSerializedSize();
            if (payloadChunkSize <= 0) {
                PulsarClientException.InvalidMessageException invalidMessageException =
                        new PulsarClientException.InvalidMessageException(
                                format("The producer %s of the topic %s sends a message with %d bytes metadata that "
                                                + "exceeds %d bytes", producerName, topic,
                                        msgMetadata.getSerializedSize(), getMaxMessageSize()));
                completeCallbackAndReleaseSemaphore(uncompressedSize, callback, invalidMessageException);
                compressedPayload.release();
                return;
            }
            payloadChunkSize = Math.min(chunkMaxMessageSize, payloadChunkSize);
            totalChunks = MathUtils.ceilDiv(Math.max(1, compressedPayload.readableBytes()), payloadChunkSize);
        }

        // chunked message also sent individually so, try to acquire send-permits
        for (int i = 0; i < (totalChunks - 1); i++) {
            if (!conf.isBlockIfQueueFull() && !canEnqueueRequest(callback, message.getSequenceId(),
                    0 /* The memory was already reserved */)) {
                compressedPayload.release();
                client.getMemoryLimitController().releaseMemory(uncompressedSize);
                semaphoreRelease(i + 1);
                return;
            }
        }

        try {
            int readStartIndex = 0;
            ChunkedMessageCtx chunkedMessageCtx = totalChunks > 1 ? ChunkedMessageCtx.get(totalChunks) : null;
            byte[] schemaVersion = totalChunks > 1 && msg.getMessageBuilder().hasSchemaVersion()
                    ? msg.getMessageBuilder().getSchemaVersion() : null;
            byte[] orderingKey = totalChunks > 1 && msg.getMessageBuilder().hasOrderingKey()
                    ? msg.getMessageBuilder().getOrderingKey() : null;
            // msg.messageId will be reset if previous message chunk is sent successfully.
            final MessageId messageId = msg.getMessageId();
            for (int chunkId = 0; chunkId < totalChunks; chunkId++) {
                // Need to reset the schemaVersion, because the schemaVersion is based on a ByteBuf object in
                // `MessageMetadata`, if we want to re-serialize the `SEND` command using a same `MessageMetadata`,
                // we need to reset the ByteBuf of the schemaVersion in `MessageMetadata`, I think we need to
                // reset `ByteBuf` objects in `MessageMetadata` after call the method `MessageMetadata#writeTo()`.
                if (chunkId > 0) {
                    if (schemaVersion != null) {
                        msg.getMessageBuilder().setSchemaVersion(schemaVersion);
                    }
                    if (orderingKey != null) {
                        msg.getMessageBuilder().setOrderingKey(orderingKey);
                    }
                }
                if (chunkId > 0 && conf.isBlockIfQueueFull() && !canEnqueueRequest(callback,
                        message.getSequenceId(), 0 /* The memory was already reserved */)) {
                    compressedPayload.release();
                    client.getMemoryLimitController().releaseMemory(uncompressedSize - readStartIndex);
                    semaphoreRelease(totalChunks - chunkId);
                    return;
                }
                synchronized (this) {
                    // Update the message metadata before computing the payload chunk size
                    // to avoid a large message cannot be split into chunks.
                    final long sequenceId = updateMessageMetadataSequenceId(msgMetadata);
                    String uuid = totalChunks > 1 ? String.format("%s-%d", producerName, sequenceId) : null;

                    serializeAndSendMessage(msg, payload, sequenceId, uuid, chunkId, totalChunks,
                            readStartIndex, payloadChunkSize, compressedPayload, compressed,
                            compressedPayload.readableBytes(), callback, chunkedMessageCtx, messageId);
                    readStartIndex = ((chunkId + 1) * payloadChunkSize);
                }
            }
        } catch (PulsarClientException e) {
            e.setSequenceId(msg.getSequenceId());
            completeCallbackAndReleaseSemaphore(uncompressedSize, callback, e);
        } catch (Throwable t) {
            completeCallbackAndReleaseSemaphore(uncompressedSize, callback,
                    new PulsarClientException(t, msg.getSequenceId()));
        }
    }

    /**
     * Update the message metadata except those fields that will be updated for chunks later.
     *
     * @param msgMetadata
     * @param uncompressedSize
     * @return the sequence id
     */
    private void updateMessageMetadata(final MessageMetadata msgMetadata, final int uncompressedSize) {
        if (!msgMetadata.hasPublishTime()) {
            msgMetadata.setPublishTime(client.getClientClock().millis());

            checkArgument(!msgMetadata.hasProducerName());

            msgMetadata.setProducerName(producerName);

            if (conf.getCompressionType() != CompressionType.NONE) {
                msgMetadata
                        .setCompression(CompressionCodecProvider.convertToWireProtocol(conf.getCompressionType()));
            }
            msgMetadata.setUncompressedSize(uncompressedSize);
        }
    }

    private long updateMessageMetadataSequenceId(final MessageMetadata msgMetadata) {
        final long sequenceId;
        if (!msgMetadata.hasSequenceId()) {
            sequenceId = msgIdGenerator++;
            msgMetadata.setSequenceId(sequenceId);
        } else {
            sequenceId = msgMetadata.getSequenceId();
        }
        return sequenceId;
    }

    @Override
    public int getNumOfPartitions() {
        return 0;
    }

    private void serializeAndSendMessage(MessageImpl<?> msg,
                                         ByteBuf payload,
                                         long sequenceId,
                                         String uuid,
                                         int chunkId,
                                         int totalChunks,
                                         int readStartIndex,
                                         int chunkMaxSizeInBytes,
                                         ByteBuf compressedPayload,
                                         boolean compressed,
                                         int compressedPayloadSize,
                                         SendCallback callback,
                                         ChunkedMessageCtx chunkedMessageCtx,
                                         MessageId messageId) throws IOException {
        ByteBuf chunkPayload = compressedPayload;
        MessageMetadata msgMetadata = msg.getMessageBuilder();
        if (totalChunks > 1 && TopicName.get(topic).isPersistent()) {
            chunkPayload = compressedPayload.slice(readStartIndex,
                    Math.min(chunkMaxSizeInBytes, chunkPayload.readableBytes() - readStartIndex));
            // don't retain last chunk payload and builder as it will be not needed for next chunk-iteration and it will
            // be released once this chunk-message is sent
            if (chunkId != totalChunks - 1) {
                chunkPayload.retain();
            }
            if (uuid != null) {
                msgMetadata.setUuid(uuid);
            }
            msgMetadata.setChunkId(chunkId)
                .setNumChunksFromMsg(totalChunks)
                .setTotalChunkMsgSize(compressedPayloadSize);
        }

        if (canAddToBatch(msg) && totalChunks <= 1) {
            if (canAddToCurrentBatch(msg)) {
                // should trigger complete the batch message, new message will add to a new batch and new batch
                // sequence id use the new message, so that broker can handle the message duplication
                if (sequenceId <= lastSequenceIdPushed) {
                    isLastSequenceIdPotentialDuplicated = true;
                    if (sequenceId <= lastSequenceIdPublished) {
                        log.warn("Message with sequence id {} is definitely a duplicate", sequenceId);
                    } else {
                        log.info("Message with sequence id {} might be a duplicate but cannot be determined at this"
                                + " time.", sequenceId);
                    }
                    doBatchSendAndAdd(msg, callback, payload);
                } else {
                    // Should flush the last potential duplicated since can't combine potential duplicated messages
                    // and non-duplicated messages into a batch.
                    if (isLastSequenceIdPotentialDuplicated) {
                        doBatchSendAndAdd(msg, callback, payload);
                    } else {
                        // handle boundary cases where message being added would exceed
                        // batch size and/or max message size
                        try {
                            boolean isBatchFull = batchMessageContainer.add(msg, callback);
                            lastSendFuture = callback.getFuture();
                            triggerSendIfFullOrScheduleFlush(isBatchFull);
                        } finally {
                            payload.release();
                        }
                    }
                    isLastSequenceIdPotentialDuplicated = false;
                }
            } else {
                doBatchSendAndAdd(msg, callback, payload);
            }
        } else {
            // in this case compression has not been applied by the caller
            // but we have to compress the payload if compression is configured
            if (!compressed) {
                chunkPayload = applyCompression(chunkPayload);
            }
            ByteBuf encryptedPayload = encryptMessage(msgMetadata, chunkPayload);

            // When publishing during replication, we need to set the correct number of message in batch
            // This is only used in tracking the publish rate stats
            int numMessages = msg.getMessageBuilder().hasNumMessagesInBatch()
                    ? msg.getMessageBuilder().getNumMessagesInBatch()
                    : 1;
            final OpSendMsg op;
            if (msg.getSchemaState() == MessageImpl.SchemaState.Ready) {
                ByteBufPair cmd = sendMessage(producerId, sequenceId, numMessages, messageId, msgMetadata,
                        encryptedPayload);
                op = OpSendMsg.create(msg, cmd, sequenceId, callback);
            } else {
                op = OpSendMsg.create(msg, null, sequenceId, callback);
                final MessageMetadata finalMsgMetadata = msgMetadata;
                op.rePopulate = () -> {
                    if (msgMetadata.hasChunkId()) {
                        // The message metadata is shared between all chunks in a large message
                        // We need to reset the chunk id for each call of this method
                        // It's safe to do that because there is only 1 thread to manipulate this message metadata
                        finalMsgMetadata.setChunkId(chunkId);
                    }
                    op.cmd = sendMessage(producerId, sequenceId, numMessages, messageId, finalMsgMetadata,
                            encryptedPayload);
                };
            }
            op.setNumMessagesInBatch(numMessages);
            op.setBatchSizeByte(encryptedPayload.readableBytes());
            if (totalChunks > 1) {
                op.totalChunks = totalChunks;
                op.chunkId = chunkId;
            }
            op.chunkedMessageCtx = chunkedMessageCtx;
            lastSendFuture = callback.getFuture();
            processOpSendMsg(op);
        }
    }

    @VisibleForTesting
    boolean populateMessageSchema(MessageImpl msg, SendCallback callback) {
        MessageMetadata msgMetadataBuilder = msg.getMessageBuilder();
        if (msg.getSchemaInternal() == schema) {
            schemaVersion.ifPresent(v -> msgMetadataBuilder.setSchemaVersion(v));
            msg.setSchemaState(MessageImpl.SchemaState.Ready);
            return true;
        }
        // If the message is from the replicator and without replicated schema
        // Which means the message is written with BYTES schema
        // So we don't need to replicate schema to the remote cluster
        if (msg.hasReplicateFrom() && msg.getSchemaInfoForReplicator() == null) {
            msg.setSchemaState(MessageImpl.SchemaState.Ready);
            return true;
        }

        if (!isMultiSchemaEnabled(true)) {
            PulsarClientException.InvalidMessageException e = new PulsarClientException.InvalidMessageException(
                    format("The producer %s of the topic %s is disabled the `MultiSchema`", producerName, topic)
                    , msg.getSequenceId());
            completeCallbackAndReleaseSemaphore(msg.getUncompressedSize(), callback, e);
            return false;
        }

        byte[] schemaVersion = schemaCache.get(msg.getSchemaHash());
        if (schemaVersion != null) {
            if (schemaVersion != SchemaVersion.Empty.bytes()) {
                msgMetadataBuilder.setSchemaVersion(schemaVersion);
            }

            msg.setSchemaState(MessageImpl.SchemaState.Ready);
        }

        return true;
    }

    private boolean rePopulateMessageSchema(MessageImpl msg) {
        byte[] schemaVersion = schemaCache.get(msg.getSchemaHash());
        if (schemaVersion == null) {
            return false;
        }

        if (schemaVersion != SchemaVersion.Empty.bytes()) {
            msg.getMessageBuilder().setSchemaVersion(schemaVersion);
        }

        msg.setSchemaState(MessageImpl.SchemaState.Ready);
        return true;
    }

    private void tryRegisterSchema(ClientCnx cnx, final MessageImpl msg, SendCallback callback, long expectedCnxEpoch) {
        if (!changeToRegisteringSchemaState()) {
            return;
        }
        SchemaInfo schemaInfo = msg.hasReplicateFrom() ? msg.getSchemaInfoForReplicator() : msg.getSchemaInfo();
        schemaInfo = Optional.ofNullable(schemaInfo)
                                        .filter(si -> si.getType().getValue() > 0)
                                        .orElse(Schema.BYTES.getSchemaInfo());
        getOrCreateSchemaAsync(cnx, schemaInfo).handle((v, ex) -> {
            if (ex != null) {
                Throwable t = FutureUtil.unwrapCompletionException(ex);
                log.warn("[{}] [{}] GetOrCreateSchema error", topic, producerName, t);
                if (t instanceof PulsarClientException.IncompatibleSchemaException) {
                    // Only the first time of failed schema registration will trigger a "recoverProcessOpSendMsgFrom".
                    if (!Broken.equals(msg.getSchemaState())) {
                        cnx.ctx().channel().eventLoop().execute(() -> {
                            synchronized (ProducerImpl.this) {
                                recoverProcessOpSendMsgFrom(cnx, msg, true, expectedCnxEpoch);
                            }
                        });
                    }
                    return null;
                }
            } else {
                log.info("[{}] [{}] GetOrCreateSchema succeed", topic, producerName);
                // In broker, if schema version is an empty byte array, it means the topic doesn't have schema.
                // In this case, we cache the schema version to `SchemaVersion.Empty.bytes()`.
                // When we need to set the schema version of the message metadata,
                // we should check if the cached schema version is `SchemaVersion.Empty.bytes()`
                if (v.length != 0) {
                    schemaCache.putIfAbsent(msg.getSchemaHash(), v);
                    msg.getMessageBuilder().setSchemaVersion(v);
                } else {
                    schemaCache.putIfAbsent(msg.getSchemaHash(), SchemaVersion.Empty.bytes());
                }
                msg.setSchemaState(MessageImpl.SchemaState.Ready);
            }
            cnx.ctx().channel().eventLoop().execute(() -> {
                synchronized (ProducerImpl.this) {
                    recoverProcessOpSendMsgFrom(cnx, msg, false, expectedCnxEpoch);
                }
            });
            return null;
        });
    }

    private CompletableFuture<byte[]> getOrCreateSchemaAsync(ClientCnx cnx, SchemaInfo schemaInfo) {
        if (!Commands.peerSupportsGetOrCreateSchema(cnx.getRemoteEndpointProtocolVersion())) {
            return FutureUtil.failedFuture(
                new PulsarClientException.NotSupportedException(
                    format("The command `GetOrCreateSchema` is not supported for the protocol version %d. "
                            + "The producer is %s, topic is %s",
                            cnx.getRemoteEndpointProtocolVersion(), producerName, topic)));
        }
        long requestId = client.newRequestId();
        ByteBuf request = Commands.newGetOrCreateSchema(requestId, topic, schemaInfo);
        log.info("[{}] [{}] GetOrCreateSchema request", topic, producerName);
        return cnx.sendGetOrCreateSchema(request, requestId);
    }

    protected ByteBuf encryptMessage(MessageMetadata msgMetadata, ByteBuf compressedPayload)
            throws PulsarClientException {

        if (!conf.isEncryptionEnabled() || msgCrypto == null) {
            return compressedPayload;
        }

        try {
            int maxSize = msgCrypto.getMaxOutputSize(compressedPayload.readableBytes());
            ByteBuf encryptedPayload = PulsarByteBufAllocator.DEFAULT.buffer(maxSize);
            ByteBuffer targetBuffer = encryptedPayload.nioBuffer(0, maxSize);

            msgCrypto.encrypt(conf.getEncryptionKeys(), conf.getCryptoKeyReader(), () -> msgMetadata,
                    compressedPayload.nioBuffer(), targetBuffer);

            encryptedPayload.writerIndex(targetBuffer.remaining());
            compressedPayload.release();
            return encryptedPayload;
        } catch (PulsarClientException e) {
            // Unless config is set to explicitly publish un-encrypted message upon failure, fail the request
            if (conf.getCryptoFailureAction() == ProducerCryptoFailureAction.SEND) {
                log.warn("[{}] [{}] Failed to encrypt message {}. Proceeding with publishing unencrypted message",
                        topic, producerName, e.getMessage());
                return compressedPayload;
            }
            throw e;
        }
    }

    protected ByteBufPair sendMessage(long producerId, long sequenceId, int numMessages,
                                      MessageId messageId, MessageMetadata msgMetadata,
                                      ByteBuf compressedPayload) {
        if (messageId instanceof MessageIdImpl) {
            return Commands.newSend(producerId, sequenceId, numMessages, getChecksumType(),
                    ((MessageIdImpl) messageId).getLedgerId(), ((MessageIdImpl) messageId).getEntryId(),
                    msgMetadata, compressedPayload);
        } else {
            return Commands.newSend(producerId, sequenceId, numMessages, getChecksumType(), -1, -1, msgMetadata,
                    compressedPayload);
        }
    }

    protected ByteBufPair sendMessage(long producerId, long lowestSequenceId, long highestSequenceId, int numMessages,
                                      MessageMetadata msgMetadata, ByteBuf compressedPayload) {
        return Commands.newSend(producerId, lowestSequenceId, highestSequenceId, numMessages, getChecksumType(),
                msgMetadata, compressedPayload);
    }

    protected ChecksumType getChecksumType() {
        if (connectionHandler.cnx() == null
                || connectionHandler.cnx().getRemoteEndpointProtocolVersion() >= brokerChecksumSupportedVersion()) {
            return ChecksumType.Crc32c;
        } else {
            return ChecksumType.None;
        }
    }

    private boolean canAddToBatch(MessageImpl<?> msg) {
        return msg.getSchemaState() == MessageImpl.SchemaState.Ready
                && isBatchMessagingEnabled() && !msg.getMessageBuilder().hasDeliverAtTime();
    }

    private boolean canAddToCurrentBatch(MessageImpl<?> msg) {
        return batchMessageContainer.haveEnoughSpace(msg)
               && (!isMultiSchemaEnabled(false) || batchMessageContainer.hasSameSchema(msg))
                && batchMessageContainer.hasSameTxn(msg);
    }

    private void triggerSendIfFullOrScheduleFlush(boolean isBatchFull) {
        if (isBatchFull) {
            batchMessageAndSend(false);
        } else {
            maybeScheduleBatchFlushTask();
        }
    }

    private void doBatchSendAndAdd(MessageImpl<?> msg, SendCallback callback, ByteBuf payload) {
        if (log.isDebugEnabled()) {
            log.debug("[{}] [{}] Closing out batch to accommodate large message with size {}", topic, producerName,
                    msg.getUncompressedSize());
        }
        try {
            batchMessageAndSend(false);
            boolean isBatchFull = batchMessageContainer.add(msg, callback);
            triggerSendIfFullOrScheduleFlush(isBatchFull);
            lastSendFuture = callback.getFuture();
        } finally {
            payload.release();
        }
    }

    private PulsarClientException getTerminalException(State state) {
        switch (state) {
            case Terminated:
                return new PulsarClientException.TopicTerminatedException(
                        format("The topic %s that the producer %s produces to has been terminated", topic,
                                producerName));
            case Closed:
                return new PulsarClientException.AlreadyClosedException(
                        format("The producer %s of the topic %s was already closed", producerName, topic));
            case ProducerFenced:
                return new PulsarClientException.ProducerFencedException(
                        format("The producer %s of the topic %s was fenced", producerName, topic));
            default:
                return new PulsarClientException.NotConnectedException();
        }
    }

    private boolean isValidProducerState(SendCallback callback, long sequenceId) {
        switch (getState()) {
        case Ready:
            // OK
        case Connecting:
            // We are OK to queue the messages on the client, it will be sent to the broker once we get the connection
        case RegisteringSchema:
            // registering schema
            return true;
        case Closing:
        case Closed:
            callback.sendComplete(
                    new PulsarClientException.AlreadyClosedException("Producer already closed", sequenceId));
            return false;
        case ProducerFenced:
            callback.sendComplete(new PulsarClientException.ProducerFencedException("Producer was fenced"));
            return false;
        case Terminated:
            callback.sendComplete(
                    new PulsarClientException.TopicTerminatedException("Topic was terminated", sequenceId));
            return false;
        case Failed:
        case Uninitialized:
        default:
            callback.sendComplete(new PulsarClientException.NotConnectedException(sequenceId));
            return false;
        }
    }

    private boolean canEnqueueRequest(SendCallback callback, long sequenceId, int payloadSize) {
        try {
            if (conf.isBlockIfQueueFull()) {
                if (semaphore.isPresent()) {
                    semaphore.get().acquire();
                }
                client.getMemoryLimitController().reserveMemory(payloadSize);
            } else {
                if (!semaphore.map(Semaphore::tryAcquire).orElse(true)) {
                    pendingQueueFullCounter.incrementAndGet();
                    callback.sendComplete(new PulsarClientException.ProducerQueueIsFullError(
                            "Producer send queue is full", sequenceId));
                    return false;
                }

                if (!client.getMemoryLimitController().tryReserveMemory(payloadSize)) {
                    semaphore.ifPresent(Semaphore::release);
                    callback.sendComplete(new PulsarClientException.MemoryBufferIsFullError(
                            "Client memory buffer is full", sequenceId));
                    return false;
                }
            }
        } catch (InterruptedException e) {
            Thread.currentThread().interrupt();
            callback.sendComplete(new PulsarClientException(e, sequenceId));
            return false;
        }

        return true;
    }

    private static final class WriteInEventLoopCallback implements Runnable {
        private ProducerImpl<?> producer;
        private ByteBufPair cmd;
        private long sequenceId;
        private ClientCnx cnx;
        private OpSendMsg op;

        static WriteInEventLoopCallback create(ProducerImpl<?> producer, ClientCnx cnx, OpSendMsg op) {
            WriteInEventLoopCallback c = RECYCLER.get();
            c.producer = producer;
            c.cnx = cnx;
            c.sequenceId = op.sequenceId;
            c.cmd = op.cmd;
            c.op = op;
            return c;
        }

        @Override
        public void run() {
            if (log.isDebugEnabled()) {
                log.debug("[{}] [{}] Sending message cnx {}, sequenceId {}", producer.topic, producer.producerName, cnx,
                        sequenceId);
            }

            try {
                cnx.ctx().writeAndFlush(cmd, cnx.ctx().voidPromise());
                op.updateSentTimestamp();
            } finally {
                recycle();
            }
        }

        private void recycle() {
            producer = null;
            cnx = null;
            cmd = null;
            sequenceId = -1;
            op = null;
            recyclerHandle.recycle(this);
        }

        private final Handle<WriteInEventLoopCallback> recyclerHandle;

        private WriteInEventLoopCallback(Handle<WriteInEventLoopCallback> recyclerHandle) {
            this.recyclerHandle = recyclerHandle;
        }

        private static final Recycler<WriteInEventLoopCallback> RECYCLER = new Recycler<WriteInEventLoopCallback>() {
            @Override
            protected WriteInEventLoopCallback newObject(Handle<WriteInEventLoopCallback> handle) {
                return new WriteInEventLoopCallback(handle);
            }
        };
    }

    private static final class LastSendFutureWrapper {
        private final CompletableFuture<MessageId> lastSendFuture;
        private static final int FALSE = 0;
        private static final int TRUE = 1;
        private static final AtomicIntegerFieldUpdater<LastSendFutureWrapper> THROW_ONCE_UPDATER =
                AtomicIntegerFieldUpdater.newUpdater(LastSendFutureWrapper.class, "throwOnce");
        private volatile int throwOnce = FALSE;

        private LastSendFutureWrapper(CompletableFuture<MessageId> lastSendFuture) {
            this.lastSendFuture = lastSendFuture;
        }
        static LastSendFutureWrapper create(CompletableFuture<MessageId> lastSendFuture) {
            return new LastSendFutureWrapper(lastSendFuture);
        }
        public CompletableFuture<Void> handleOnce() {
            return lastSendFuture.handle((ignore, t) -> {
                if (t != null && THROW_ONCE_UPDATER.compareAndSet(this, FALSE, TRUE)) {
                    throw FutureUtil.wrapToCompletionException(t);
                }
                return null;
            });
        }
    }


    @Override
    public synchronized CompletableFuture<Void> closeAsync() {
        final State currentState = getAndUpdateState(state -> {
            if (state == State.Closed) {
                return state;
            }
            return State.Closing;
        });

        if (currentState == State.Closed || currentState == State.Closing) {
            return CompletableFuture.completedFuture(null);
        }

        closeProducerTasks();

        ClientCnx cnx = cnx();
        if (cnx == null || currentState != State.Ready) {
            log.info("[{}] [{}] Closed Producer (not connected)", topic, producerName);
            closeAndClearPendingMessages();
            return CompletableFuture.completedFuture(null);
        }

        long requestId = client.newRequestId();
        ByteBuf cmd = Commands.newCloseProducer(producerId, requestId);

        CompletableFuture<Void> closeFuture = new CompletableFuture<>();
        cnx.sendRequestWithId(cmd, requestId).handle((v, exception) -> {
            cnx.removeProducer(producerId);
            if (exception == null || !cnx.ctx().channel().isActive()) {
                // Either we've received the success response for the close producer command from the broker, or the
                // connection did break in the meantime. In any case, the producer is gone.
                log.info("[{}] [{}] Closed Producer", topic, producerName);
                closeAndClearPendingMessages();
                closeFuture.complete(null);
            } else {
                closeFuture.completeExceptionally(exception);
            }

            return null;
        });

        return closeFuture;
    }

    @VisibleForTesting
    protected synchronized void closeAndClearPendingMessages() {
        setState(State.Closed);
        client.cleanupProducer(this);
        PulsarClientException ex = new PulsarClientException.AlreadyClosedException(
                format("The producer %s of the topic %s was already closed when closing the producers",
                        producerName, topic));
        // Use null for cnx to ensure that the pending messages are failed immediately
        failPendingMessages(null, ex);
    }

    @Override
    public boolean isConnected() {
        return getCnxIfReady() != null;
    }

    /**
     * Hook method for testing. By returning null, it's possible to prevent messages
     * being delivered to the broker.
     *
     * @return cnx if OpSend messages should be written to open connection. Caller must
     * verify that the returned cnx is not null before using reference.
     */
    protected ClientCnx getCnxIfReady() {
        State state = getState();
        // When a producer is publishing with multiple schema, it may be switched to a "RegisteringSchema" state, even
        // if the connection is established.
        if (State.Ready.equals(state) || State.RegisteringSchema.equals(state)) {
            return connectionHandler.cnx();
        } else {
            return null;
        }
    }

    @Override
    public long getLastDisconnectedTimestamp() {
        return connectionHandler.lastConnectionClosedTimestamp;
    }

    public boolean isWritable() {
        ClientCnx cnx = connectionHandler.cnx();
        return cnx != null && cnx.channel().isWritable();
    }

    public void terminated(ClientCnx cnx) {
        State previousState = getAndUpdateState(state -> (state == State.Closed ? State.Closed : State.Terminated));
        if (previousState != State.Terminated && previousState != State.Closed) {
            log.info("[{}] [{}] The topic has been terminated", topic, producerName);
            setClientCnx(null);
            synchronized (this) {
                failPendingMessages(cnx,
                        new PulsarClientException.TopicTerminatedException(
                                format("The topic %s that the producer %s produces to has been terminated",
                                        topic, producerName)));
            }
        }
    }

    protected void ackReceived(ClientCnx cnx, long sequenceId, long highestSequenceId, long ledgerId, long entryId) {
        OpSendMsg op = null;
        synchronized (this) {
            op = pendingMessages.peek();
            if (op == null) {
                if (log.isDebugEnabled()) {
                    log.debug("[{}] [{}] Got ack for timed out msg {} - {}",
                            topic, producerName, sequenceId, highestSequenceId);
                }
                return;
            }

            if (sequenceId > op.sequenceId) {
                log.warn("[{}] [{}] Got ack for msg. expecting: {} - {} - got: {} - {} - queue-size: {}",
                        topic, producerName, op.sequenceId, op.highestSequenceId, sequenceId, highestSequenceId,
                        pendingMessages.messagesCount());
                // Force connection closing so that messages can be re-transmitted in a new connection
                cnx.channel().close();
                return;
            } else if (sequenceId < op.sequenceId) {
                // Ignoring the ack since it's referring to a message that has already timed out.
                if (log.isDebugEnabled()) {
                    log.debug("[{}] [{}] Got ack for timed out msg. expecting: {} - {} - got: {} - {}",
                            topic, producerName, op.sequenceId, op.highestSequenceId, sequenceId, highestSequenceId);
                }
                return;
            } else {
                // Add check `sequenceId >= highestSequenceId` for backward compatibility.
                if (sequenceId >= highestSequenceId || highestSequenceId == op.highestSequenceId) {
                    // Message was persisted correctly
                    if (log.isDebugEnabled()) {
                        log.debug("[{}] [{}] Received ack for msg {} ", topic, producerName, sequenceId);
                    }
                    pendingMessages.remove();
                    releaseSemaphoreForSendOp(op);
                } else {
                    log.warn("[{}] [{}] Got ack for batch msg error. expecting: {} - {} - got: {} - {} - queue-size: {}"
                                    + "",
                            topic, producerName, op.sequenceId, op.highestSequenceId, sequenceId, highestSequenceId,
                            pendingMessages.messagesCount());
                    // Force connection closing so that messages can be re-transmitted in a new connection
                    cnx.channel().close();
                    return;
                }
            }
        }

        OpSendMsg finalOp = op;
        LAST_SEQ_ID_PUBLISHED_UPDATER.getAndUpdate(this, last -> Math.max(last, getHighestSequenceId(finalOp)));
        op.setMessageId(ledgerId, entryId, partitionIndex);
        if (op.totalChunks > 1) {
            if (op.chunkId == 0) {
                op.chunkedMessageCtx.firstChunkMessageId = new MessageIdImpl(ledgerId, entryId, partitionIndex);
            } else if (op.chunkId == op.totalChunks - 1) {
                op.chunkedMessageCtx.lastChunkMessageId = new MessageIdImpl(ledgerId, entryId, partitionIndex);
                op.setMessageId(op.chunkedMessageCtx.getChunkMessageId());
            }
        }


        // if message is chunked then call callback only on last chunk
        if (op.totalChunks <= 1 || (op.chunkId == op.totalChunks - 1)) {
            try {
                // Need to protect ourselves from any exception being thrown in the future handler from the
                // application
                op.sendComplete(null);
            } catch (Throwable t) {
                log.warn("[{}] [{}] Got exception while completing the callback for msg {}:", topic,
                        producerName, sequenceId, t);
            }
        }
        ReferenceCountUtil.safeRelease(op.cmd);
        op.recycle();
    }

    protected long getHighestSequenceId(OpSendMsg op) {
        return Math.max(op.highestSequenceId, op.sequenceId);
    }

    protected void releaseSemaphoreForSendOp(OpSendMsg op) {

        semaphoreRelease(isBatchMessagingEnabled() ? op.numMessagesInBatch : 1);

        client.getMemoryLimitController().releaseMemory(op.uncompressedSize);
    }

    private void completeCallbackAndReleaseSemaphore(long payloadSize, SendCallback callback, Exception exception) {
        semaphore.ifPresent(Semaphore::release);
        client.getMemoryLimitController().releaseMemory(payloadSize);
        callback.sendComplete(exception);
    }

    /**
     * Checks message checksum to retry if message was corrupted while sending to broker. Recomputes checksum of the
     * message header-payload again.
     * <ul>
     * <li><b>if matches with existing checksum</b>: it means message was corrupt while sending to broker. So, resend
     * message</li>
     * <li><b>if doesn't match with existing checksum</b>: it means message is already corrupt and can't retry again.
     * So, fail send-message by failing callback</li>
     * </ul>
     *
     * @param cnx
     * @param sequenceId
     */
    protected synchronized void recoverChecksumError(ClientCnx cnx, long sequenceId) {
        OpSendMsg op = pendingMessages.peek();
        if (op == null) {
            if (log.isDebugEnabled()) {
                log.debug("[{}] [{}] Got send failure for timed out msg {}", topic, producerName, sequenceId);
            }
        } else {
            long expectedSequenceId = getHighestSequenceId(op);
            if (sequenceId == expectedSequenceId) {
                boolean corrupted = !verifyLocalBufferIsNotCorrupted(op);
                if (corrupted) {
                    // remove message from pendingMessages queue and fail callback
                    pendingMessages.remove();
                    releaseSemaphoreForSendOp(op);
                    try {
                        op.sendComplete(
                            new PulsarClientException.ChecksumException(
                                format("The checksum of the message which is produced by producer %s to the topic "
                                        + "%s is corrupted", producerName, topic)));
                    } catch (Throwable t) {
                        log.warn("[{}] [{}] Got exception while completing the callback for msg {}:", topic,
                                producerName, sequenceId, t);
                    }
                    ReferenceCountUtil.safeRelease(op.cmd);
                    op.recycle();
                    return;
                } else {
                    if (log.isDebugEnabled()) {
                        log.debug("[{}] [{}] Message is not corrupted, retry send-message with sequenceId {}", topic,
                                producerName, sequenceId);
                    }
                }

            } else {
                if (log.isDebugEnabled()) {
                    log.debug("[{}] [{}] Corrupt message is already timed out {}", topic, producerName, sequenceId);
                }
            }
        }
        // as msg is not corrupted : let producer resend pending-messages again including checksum failed message
        resendMessages(cnx, this.connectionHandler.getEpoch());
    }

    protected synchronized void recoverNotAllowedError(long sequenceId, String errorMsg) {
        OpSendMsg op = pendingMessages.peek();
        if (op != null && sequenceId == getHighestSequenceId(op)) {
            pendingMessages.remove();
            releaseSemaphoreForSendOp(op);
            try {
                op.sendComplete(
                        new PulsarClientException.NotAllowedException(errorMsg));
            } catch (Throwable t) {
                log.warn("[{}] [{}] Got exception while completing the callback for msg {}:", topic,
                        producerName, sequenceId, t);
            }
            ReferenceCountUtil.safeRelease(op.cmd);
            op.recycle();
        }
    }

    /**
     * Computes checksum again and verifies it against existing checksum. If checksum doesn't match it means that
     * message is corrupt.
     *
     * @param op
     * @return returns true only if message is not modified and computed-checksum is same as previous checksum else
     *         return false that means that message is corrupted. Returns true if checksum is not present.
     */
    protected boolean verifyLocalBufferIsNotCorrupted(OpSendMsg op) {
        ByteBufPair msg = op.cmd;

        if (msg != null) {
            ByteBuf headerFrame = msg.getFirst();
            headerFrame.markReaderIndex();
            try {
                // skip bytes up to checksum index
                headerFrame.skipBytes(4); // skip [total-size]
                int cmdSize = (int) headerFrame.readUnsignedInt();
                headerFrame.skipBytes(cmdSize);
                // verify if checksum present
                if (hasChecksum(headerFrame)) {
                    int checksum = readChecksum(headerFrame);
                    // msg.readerIndex is already at header-payload index, Recompute checksum for headers-payload
                    int metadataChecksum = computeChecksum(headerFrame);
                    long computedChecksum = resumeChecksum(metadataChecksum, msg.getSecond());
                    return checksum == computedChecksum;
                } else {
                    log.warn("[{}] [{}] checksum is not present into message with id {}", topic, producerName,
                            op.sequenceId);
                }
            } finally {
                headerFrame.resetReaderIndex();
            }
            return true;
        } else {
            log.warn("[{}] Failed while casting empty ByteBufPair, ", producerName);
            return false;
        }
    }

    static class ChunkedMessageCtx extends AbstractReferenceCounted {
        protected MessageIdImpl firstChunkMessageId;
        protected MessageIdImpl lastChunkMessageId;

        public ChunkMessageIdImpl getChunkMessageId() {
            return new ChunkMessageIdImpl(firstChunkMessageId, lastChunkMessageId);
        }

        private static final Recycler<ProducerImpl.ChunkedMessageCtx> RECYCLER =
                new Recycler<ProducerImpl.ChunkedMessageCtx>() {
                    protected ProducerImpl.ChunkedMessageCtx newObject(
                            Recycler.Handle<ProducerImpl.ChunkedMessageCtx> handle) {
                        return new ProducerImpl.ChunkedMessageCtx(handle);
                    }
                };

        public static ChunkedMessageCtx get(int totalChunks) {
            ChunkedMessageCtx chunkedMessageCtx = RECYCLER.get();
            chunkedMessageCtx.setRefCnt(totalChunks);
            return chunkedMessageCtx;
        }

        private final Handle<ProducerImpl.ChunkedMessageCtx> recyclerHandle;

        private ChunkedMessageCtx(Handle<ChunkedMessageCtx> recyclerHandle) {
            this.recyclerHandle = recyclerHandle;
        }

        @Override
        protected void deallocate() {
            this.firstChunkMessageId = null;
            this.lastChunkMessageId = null;
            recyclerHandle.recycle(this);
        }

        @Override
        public ReferenceCounted touch(Object hint) {
            return this;
        }
    }

    protected static final class OpSendMsg {
        MessageImpl<?> msg;
        List<MessageImpl<?>> msgs;
        ByteBufPair cmd;
        SendCallback callback;
        Runnable rePopulate;
        ChunkedMessageCtx chunkedMessageCtx;
        long uncompressedSize;
        long sequenceId;
        long createdAt;
        long firstSentAt;
        long lastSentAt;
        int retryCount;
        long batchSizeByte = 0;
        int numMessagesInBatch = 1;
        long highestSequenceId;
        int totalChunks = 0;
        int chunkId = -1;

        void initialize() {
            msg = null;
            msgs = null;
            cmd = null;
            callback = null;
            rePopulate = null;
            sequenceId = -1L;
            createdAt = -1L;
            firstSentAt = -1L;
            lastSentAt = -1L;
            highestSequenceId = -1L;
            totalChunks = 0;
            chunkId = -1;
            uncompressedSize = 0;
            retryCount = 0;
            batchSizeByte = 0;
            numMessagesInBatch = 1;
            chunkedMessageCtx = null;
        }

        static OpSendMsg create(MessageImpl<?> msg, ByteBufPair cmd, long sequenceId, SendCallback callback) {
            OpSendMsg op = RECYCLER.get();
            op.initialize();
            op.msg = msg;
            op.cmd = cmd;
            op.callback = callback;
            op.sequenceId = sequenceId;
            op.createdAt = System.nanoTime();
            op.uncompressedSize = msg.getUncompressedSize();
            return op;
        }

        static OpSendMsg create(List<MessageImpl<?>> msgs, ByteBufPair cmd, long sequenceId, SendCallback callback,
                                int batchAllocatedSize) {
            OpSendMsg op = RECYCLER.get();
            op.initialize();
            op.msgs = msgs;
            op.cmd = cmd;
            op.callback = callback;
            op.sequenceId = sequenceId;
            op.createdAt = System.nanoTime();
            op.uncompressedSize = 0;
            for (int i = 0; i < msgs.size(); i++) {
                op.uncompressedSize += msgs.get(i).getUncompressedSize();
            }
            op.uncompressedSize += batchAllocatedSize;
            return op;
        }

        static OpSendMsg create(List<MessageImpl<?>> msgs, ByteBufPair cmd, long lowestSequenceId,
                                long highestSequenceId,  SendCallback callback, int batchAllocatedSize) {
            OpSendMsg op = RECYCLER.get();
            op.initialize();
            op.msgs = msgs;
            op.cmd = cmd;
            op.callback = callback;
            op.sequenceId = lowestSequenceId;
            op.highestSequenceId = highestSequenceId;
            op.createdAt = System.nanoTime();
            op.uncompressedSize = 0;
            for (int i = 0; i < msgs.size(); i++) {
                op.uncompressedSize += msgs.get(i).getUncompressedSize();
            }
            op.uncompressedSize += batchAllocatedSize;
            return op;
        }

        void updateSentTimestamp() {
            this.lastSentAt = System.nanoTime();
            if (this.firstSentAt == -1L) {
                this.firstSentAt = this.lastSentAt;
            }
            ++this.retryCount;
        }

        void sendComplete(final Exception e) {
            SendCallback callback = this.callback;
            if (null != callback) {
                Exception finalEx = e;
                if (finalEx instanceof TimeoutException) {
                    TimeoutException te = (TimeoutException) e;
                    long sequenceId = te.getSequenceId();
                    long ns = System.nanoTime();
                    //firstSentAt and lastSentAt maybe -1, it means that the message didn't flush to channel.
                    String errMsg = String.format(
                        "%s : createdAt %s seconds ago, firstSentAt %s seconds ago, lastSentAt %s seconds ago, "
                                + "retryCount %s",
                        te.getMessage(),
                        RelativeTimeUtil.nsToSeconds(ns - this.createdAt),
                        RelativeTimeUtil.nsToSeconds(this.firstSentAt <= 0
                                ? this.firstSentAt
                                : ns - this.firstSentAt),
                        RelativeTimeUtil.nsToSeconds(this.lastSentAt <= 0
                                ? this.lastSentAt
                                : ns - this.lastSentAt),
                        retryCount
                    );

                    finalEx = new TimeoutException(errMsg, sequenceId);
                }

                callback.sendComplete(finalEx);
            }
        }

        void recycle() {
            ReferenceCountUtil.safeRelease(chunkedMessageCtx);
            initialize();
            recyclerHandle.recycle(this);
        }

        void setNumMessagesInBatch(int numMessagesInBatch) {
            this.numMessagesInBatch = numMessagesInBatch;
        }

        void setBatchSizeByte(long batchSizeByte) {
            this.batchSizeByte = batchSizeByte;
        }

        void setMessageId(long ledgerId, long entryId, int partitionIndex) {
            if (msg != null) {
                msg.setMessageId(new MessageIdImpl(ledgerId, entryId, partitionIndex));
            } else if (msgs.size() == 1) {
                // If there is only one message in batch, the producer will publish messages like non-batch
                msgs.get(0).setMessageId(new MessageIdImpl(ledgerId, entryId, partitionIndex));
            } else {
                for (int batchIndex = 0; batchIndex < msgs.size(); batchIndex++) {
                    msgs.get(batchIndex)
                            .setMessageId(new BatchMessageIdImpl(ledgerId, entryId, partitionIndex, batchIndex));
                }
            }
        }

        void setMessageId(ChunkMessageIdImpl chunkMessageId) {
            if (msg != null) {
                msg.setMessageId(chunkMessageId);
            }
        }

        public int getMessageHeaderAndPayloadSize() {
            if (cmd == null) {
                return 0;
            }
            ByteBuf cmdHeader = cmd.getFirst();
            cmdHeader.markReaderIndex();
            int totalSize = cmdHeader.readInt();
            int cmdSize = cmdHeader.readInt();
            // The totalSize includes:
            // | cmdLength | cmdSize | magic and checksum | msgMetadataLength | msgMetadata |
            // | --------- | ------- | ------------------ | ----------------- | ----------- |
            // | 4         |         | 6                  | 4                 |             |
            int msgHeadersAndPayloadSize = totalSize - 4 - cmdSize - 6 - 4;
            cmdHeader.resetReaderIndex();
            return msgHeadersAndPayloadSize;
        }

        private OpSendMsg(Handle<OpSendMsg> recyclerHandle) {
            this.recyclerHandle = recyclerHandle;
        }

        private final Handle<OpSendMsg> recyclerHandle;
        private static final Recycler<OpSendMsg> RECYCLER = new Recycler<OpSendMsg>() {
            @Override
            protected OpSendMsg newObject(Handle<OpSendMsg> handle) {
                return new OpSendMsg(handle);
            }
        };
    }


    /**
     * Queue implementation that is used as the pending messages queue.
     *
     * This implementation postpones adding of new OpSendMsg entries that happen
     * while the forEach call is in progress. This is needed for preventing
     * ConcurrentModificationExceptions that would occur when the forEach action
     * calls the add method via a callback in user code.
     *
     * This queue is not thread safe.
     */
    protected static class OpSendMsgQueue implements Iterable<OpSendMsg> {
        @VisibleForTesting
        final ArrayDeque<OpSendMsg> delegate = new ArrayDeque<>();
        private int forEachDepth = 0;
        private List<OpSendMsg> postponedOpSendMgs;
        private final AtomicInteger messagesCount = new AtomicInteger(0);

        @Override
        public void forEach(Consumer<? super OpSendMsg> action) {
            try {
                // track any forEach call that is in progress in the current call stack
                // so that adding a new item while iterating doesn't cause ConcurrentModificationException
                forEachDepth++;
                delegate.forEach(action);
            } finally {
                forEachDepth--;
                // if this is the top-most forEach call and there are postponed items, add them
                if (forEachDepth == 0 && postponedOpSendMgs != null && !postponedOpSendMgs.isEmpty()) {
                    delegate.addAll(postponedOpSendMgs);
                    postponedOpSendMgs.clear();
                }
            }
        }

        public boolean add(OpSendMsg o) {
            // postpone adding to the queue while forEach iteration is in progress
            messagesCount.addAndGet(o.numMessagesInBatch);
            if (forEachDepth > 0) {
                if (postponedOpSendMgs == null) {
                    postponedOpSendMgs = new ArrayList<>();
                }
                return postponedOpSendMgs.add(o);
            } else {
                return delegate.add(o);
            }
        }

        public void clear() {
            delegate.clear();
            messagesCount.set(0);
        }

        public OpSendMsg remove() {
            OpSendMsg op = delegate.remove();
            if (op != null) {
                messagesCount.addAndGet(-op.numMessagesInBatch);
            }
            return op;
        }

        public OpSendMsg peek() {
            return delegate.peek();
        }

        public int messagesCount() {
            return messagesCount.get();
        }

        public int size() {
            return delegate.size();
        }

        @Override
        public Iterator<OpSendMsg> iterator() {
            Iterator<OpSendMsg> delegateIterator = delegate.iterator();
            return new Iterator<OpSendMsg>() {
                OpSendMsg currentOp;

                @Override
                public boolean hasNext() {
                    return delegateIterator.hasNext();
                }

                @Override
                public OpSendMsg next() {
                    currentOp = delegateIterator.next();
                    return currentOp;
                }

                @Override
                public void remove() {
                    delegateIterator.remove();
                    if (currentOp != null) {
                       messagesCount.addAndGet(-currentOp.numMessagesInBatch);
                       currentOp = null;
                     }
                }

                @Override
                public void forEachRemaining(Consumer<? super OpSendMsg> action) {
                    delegateIterator.forEachRemaining(action);
                }
            };
        }
    }


    @Override
    public CompletableFuture<Void> connectionOpened(final ClientCnx cnx) {
        previousExceptions.clear();
        getConnectionHandler().setMaxMessageSize(cnx.getMaxMessageSize());
        setChunkMaxMessageSize();

        final long epoch;
        synchronized (this) {
            // Because the state could have been updated while retrieving the connection, we set it back to connecting,
            // as long as the change from current state to connecting is a valid state change.
            if (!changeToConnecting()) {
                if (getState() == State.Closing || getState() == State.Closed) {
                    // Producer was closed while reconnecting, close the connection to make sure the broker
                    // drops the producer on its side
                    failPendingMessages(cnx,
                            new PulsarClientException.ProducerFencedException("producer has been closed"));
                }
                return CompletableFuture.completedFuture(null);
            }
            // We set the cnx reference before registering the producer on the cnx, so if the cnx breaks before creating
            // the producer, it will try to grab a new cnx. We also increment and get the epoch value for the producer.
            epoch = connectionHandler.switchClientCnx(cnx);
        }
        cnx.registerProducer(producerId, this);

        log.info("[{}] [{}] Creating producer on cnx {}", topic, producerName, cnx.ctx().channel());

        long requestId = client.newRequestId();

        PRODUCER_DEADLINE_UPDATER
            .compareAndSet(this, 0, System.currentTimeMillis() + client.getConfiguration().getOperationTimeoutMs());

        SchemaInfo schemaInfo = null;
        if (schema != null) {
            if (schema.getSchemaInfo() != null) {
                if (schema.getSchemaInfo().getType() == SchemaType.JSON) {
                    // for backwards compatibility purposes
                    // JSONSchema originally generated a schema for pojo based of of the JSON schema standard
                    // but now we have standardized on every schema to generate an Avro based schema
                    if (Commands.peerSupportJsonSchemaAvroFormat(cnx.getRemoteEndpointProtocolVersion())) {
                        schemaInfo = schema.getSchemaInfo();
                    } else if (schema instanceof JSONSchema){
                        JSONSchema jsonSchema = (JSONSchema) schema;
                        schemaInfo = jsonSchema.getBackwardsCompatibleJsonSchemaInfo();
                    } else {
                        schemaInfo = schema.getSchemaInfo();
                    }
                } else if (schema.getSchemaInfo().getType() == SchemaType.BYTES
                        || schema.getSchemaInfo().getType() == SchemaType.NONE) {
                    // don't set schema info for Schema.BYTES
                    schemaInfo = null;
                } else {
                    schemaInfo = schema.getSchemaInfo();
                }
            }
        }

        final CompletableFuture<Void> future = new CompletableFuture<>();
        cnx.sendRequestWithId(
                Commands.newProducer(topic, producerId, requestId, producerName, conf.isEncryptionEnabled(), metadata,
                        schemaInfo, epoch, userProvidedProducerName,
                        conf.getAccessMode(), topicEpoch, client.conf.isEnableTransaction(),
                        conf.getInitialSubscriptionName()),
                requestId).thenAccept(response -> {
                    String producerName = response.getProducerName();
                    long lastSequenceId = response.getLastSequenceId();
                    schemaVersion = Optional.ofNullable(response.getSchemaVersion());
                    schemaVersion.ifPresent(v -> schemaCache.put(SchemaHash.of(schema), v));

                    // We are now reconnected to broker and clear to send messages. Re-send all pending messages and
                    // set the cnx pointer so that new messages will be sent immediately
                    synchronized (ProducerImpl.this) {
                        State state = getState();
                        if (state == State.Closing || state == State.Closed) {
                            // Producer was closed while reconnecting, close the connection to make sure the broker
                            // drops the producer on its side
                            cnx.removeProducer(producerId);
                    failPendingMessages(cnx,
                            new PulsarClientException.ProducerFencedException("producer has been closed"));
                            cnx.channel().close();
                            future.complete(null);
                            return;
                        }
                        resetBackoff();

                        log.info("[{}] [{}] Created producer on cnx {}", topic, producerName, cnx.ctx().channel());
                        connectionId = cnx.ctx().channel().toString();
                        connectedSince = DateFormatter.now();
                        if (conf.getAccessMode() != ProducerAccessMode.Shared && !topicEpoch.isPresent()) {
                            log.info("[{}] [{}] Producer epoch is {}", topic, producerName, response.getTopicEpoch());
                        }
                        topicEpoch = response.getTopicEpoch();

                        if (this.producerName == null) {
                            this.producerName = producerName;
                        }

                        if (this.msgIdGenerator == 0 && conf.getInitialSequenceId() == null) {
                            // Only update sequence id generator if it wasn't already modified. That means we only want
                            // to update the id generator the first time the producer gets established, and ignore the
                            // sequence id sent by broker in subsequent producer reconnects
                            this.lastSequenceIdPublished = lastSequenceId;
                            this.msgIdGenerator = lastSequenceId + 1;
                        }

                        resendMessages(cnx, epoch);
                    }
                    future.complete(null);
                }).exceptionally((e) -> {
                    Throwable cause = e.getCause();
                    cnx.removeProducer(producerId);
                    State state = getState();
                    if (state == State.Closing || state == State.Closed) {
                        // Producer was closed while reconnecting, close the connection to make sure the broker
                        // drops the producer on its side
                        cnx.channel().close();
                        future.complete(null);
                        return null;
                    }

                    if (cause instanceof TimeoutException) {
                        // Creating the producer has timed out. We need to ensure the broker closes the producer
                        // in case it was indeed created, otherwise it might prevent new create producer operation,
                        // since we are not necessarily closing the connection.
                        long closeRequestId = client.newRequestId();
                        ByteBuf cmd = Commands.newCloseProducer(producerId, closeRequestId);
                        cnx.sendRequestWithId(cmd, closeRequestId);
                    }

                    // Close the producer since topic does not exist.
                    if (isUnrecoverableError(cause)) {
                        closeWhenReceivedUnrecoverableError(cause, cnx);
                        future.complete(null);
                        return null;
                    }
                    if (cause instanceof PulsarClientException.ProducerBlockedQuotaExceededException) {
                        synchronized (this) {
                            log.warn("[{}] [{}] Topic backlog quota exceeded. Throwing Exception on producer.", topic,
                                    producerName);

                            if (log.isDebugEnabled()) {
                                log.debug("[{}] [{}] Pending messages: {}", topic, producerName,
                                        pendingMessages.messagesCount());
                            }

                            PulsarClientException bqe = new PulsarClientException.ProducerBlockedQuotaExceededException(
                                format("The backlog quota of the topic %s that the producer %s produces to is exceeded",
                                    topic, producerName));
                            failPendingMessages(cnx(), bqe);
                        }
                    } else if (cause instanceof PulsarClientException.ProducerBlockedQuotaExceededError) {
                        log.warn("[{}] [{}] Producer is blocked on creation because backlog exceeded on topic.",
                                producerName, topic);
                    } else if (PulsarClientException.isRetriableError(cause)) {
                        log.info("[{}] [{}] Temporary error in creating producer: {}", topic,
                                producerName, cause.getMessage());
                    } else {
                        log.error("[{}] [{}] Failed to create producer: {}", topic, producerName, cause.getMessage());
                    }

                    if (cause instanceof PulsarClientException.TopicTerminatedException) {
                        setState(State.Terminated);
                        synchronized (this) {
                            failPendingMessages(cnx(), (PulsarClientException) cause);
                        }
                        producerCreatedFuture.completeExceptionally(cause);
                        closeProducerTasks();
                        client.cleanupProducer(this);
                    } else if (cause instanceof PulsarClientException.ProducerFencedException) {
                        setState(State.ProducerFenced);
                        synchronized (this) {
                            failPendingMessages(cnx(), (PulsarClientException) cause);
                        }
                        producerCreatedFuture.completeExceptionally(cause);
                        closeProducerTasks();
                        client.cleanupProducer(this);
                    } else if (producerCreatedFuture.isDone()
                            || (PulsarClientException.isRetriableError(cause)
                            && System.currentTimeMillis() < PRODUCER_DEADLINE_UPDATER.get(ProducerImpl.this))) {
                        // Either we had already created the producer once (producerCreatedFuture.isDone()) or we are
                        // still within the initial timeout budget and we are dealing with a retriable error
                        future.completeExceptionally(cause);
                    } else {
                        setState(State.Failed);
                        producerCreatedFuture.completeExceptionally(cause);
                        closeProducerTasks();
                        client.cleanupProducer(this);
                        Timeout timeout = sendTimeout;
                        if (timeout != null) {
                            timeout.cancel();
                            sendTimeout = null;
                        }
                    }
                    if (!future.isDone()) {
                        future.complete(null);
                    }
                    return null;
                });
        return future;
    }

    protected boolean isUnrecoverableError(Throwable t) {
        // TopicDoesNotExistException: topic has been deleted.
        // NotFoundException: topic has been deleted.
        // IllegalStateException: producer has been closed.
        return (t instanceof PulsarClientException.TopicDoesNotExistException) || (t instanceof IllegalStateException)
                || (t instanceof PulsarClientException.NotFoundException);
    }

    protected void closeWhenReceivedUnrecoverableError(Throwable t, ClientCnx cnx) {
        final String cnxStr = cnx == null ? "null" : String.valueOf(cnx.channel().remoteAddress());
        log.warn("[{}][{}] {} Closed producer because get an error that does not support to retry: {} {}",
                topic, producerName, cnxStr, t.getClass().getName(), t.getMessage());
        closeAsync().whenComplete((v, ex) -> {
            if (ex != null) {
                log.error("Failed to close producer on TopicDoesNotExistException.", ex);
            }
            producerCreatedFuture.completeExceptionally(t);
        });
    }

    @Override
    public boolean connectionFailed(PulsarClientException exception) {
        boolean nonRetriableError = !PulsarClientException.isRetriableError(exception);
        boolean timeout = System.currentTimeMillis() > lookupDeadline;
        if (nonRetriableError || timeout) {
            exception.setPreviousExceptions(previousExceptions);
            if (producerCreatedFuture.completeExceptionally(exception)) {
                if (nonRetriableError) {
                    log.info("[{}] Producer creation failed for producer {} with unretriableError = {}",
                            topic, producerId, exception.getMessage());
                } else {
                    log.info("[{}] Producer creation failed for producer {} after producerTimeout", topic, producerId);
                }
                closeProducerTasks();
                setState(State.Failed);
                client.cleanupProducer(this);
                return false;
            } else {
                Throwable actError = FutureUtil.unwrapCompletionException(exception);
                if (isUnrecoverableError(actError)) {
                    closeWhenReceivedUnrecoverableError(actError, null);
                    return false;
                }
            }
        } else {
            previousExceptions.add(exception);
        }
        return true;
    }

    private void closeProducerTasks() {
        Timeout timeout = sendTimeout;
        if (timeout != null) {
            timeout.cancel();
            sendTimeout = null;
        }

        if (keyGeneratorTask != null && !keyGeneratorTask.isCancelled()) {
            keyGeneratorTask.cancel(false);
        }

        stats.cancelStatsTimeout();
    }

    private void resendMessages(ClientCnx cnx, long expectedEpoch) {
        cnx.ctx().channel().eventLoop().execute(() -> {
            synchronized (ProducerImpl.this) {
                if (getState() == State.Closing || getState() == State.Closed) {
                    // Producer was closed while reconnecting, close the connection to make sure the broker
                    // drops the producer on its side
                    cnx.channel().close();
                    return;
                }

                int messagesToResend = pendingMessages.messagesCount();
                if (pendingMessages.size() == 0) {
                    if (log.isDebugEnabled()) {
                        log.debug("[{}] [{}] No pending messages to resend {}", topic, producerName, messagesToResend);
                    }
                    if (changeToReadyState()) {
                        producerCreatedFuture.complete(ProducerImpl.this);
                        scheduleBatchFlushTask(0);
                        return;
                    } else {
                        // Producer was closed while reconnecting, close the connection to make sure the broker
                        // drops the producer on its side
                        cnx.channel().close();
                        return;
                    }

                }

                log.info("[{}] [{}] Re-Sending {} messages to server", topic, producerName, messagesToResend);
                recoverProcessOpSendMsgFrom(cnx, null, false, expectedEpoch);
            }
        });
    }

    /**
     * Strips checksum from {@link OpSendMsg} command if present else ignore it.
     *
     * @param op
     */
    private void stripChecksum(OpSendMsg op) {
        ByteBufPair msg = op.cmd;
        if (msg != null) {
            int totalMsgBufSize = msg.readableBytes();
            ByteBuf headerFrame = msg.getFirst();
            headerFrame.markReaderIndex();
            try {
                headerFrame.skipBytes(4); // skip [total-size]
                int cmdSize = (int) headerFrame.readUnsignedInt();

                // verify if checksum present
                headerFrame.skipBytes(cmdSize);

                if (!hasChecksum(headerFrame)) {
                    return;
                }

                int headerSize = 4 + 4 + cmdSize; // [total-size] [cmd-length] [cmd-size]
                int checksumSize = 4 + 2; // [magic-number] [checksum-size]
                int checksumMark = (headerSize + checksumSize); // [header-size] [checksum-size]
                int metaPayloadSize = (totalMsgBufSize - checksumMark); // metadataPayload = totalSize - checksumMark
                int newTotalFrameSizeLength = 4 + cmdSize + metaPayloadSize; // new total-size without checksum
                headerFrame.resetReaderIndex();
                int headerFrameSize = headerFrame.readableBytes();

                headerFrame.setInt(0, newTotalFrameSizeLength); // rewrite new [total-size]
                ByteBuf metadata = headerFrame.slice(checksumMark, headerFrameSize - checksumMark); // sliced only
                                                                                                    // metadata
                headerFrame.writerIndex(headerSize); // set headerFrame write-index to overwrite metadata over checksum
                metadata.readBytes(headerFrame, metadata.readableBytes());
                headerFrame.capacity(headerFrameSize - checksumSize); // reduce capacity by removed checksum bytes
            } finally {
                headerFrame.resetReaderIndex();
            }
        } else {
            log.warn("[{}] Failed while casting null into ByteBufPair", producerName);
        }
    }

    public int brokerChecksumSupportedVersion() {
        return ProtocolVersion.v6.getValue();
    }

    @Override
    String getHandlerName() {
        return producerName;
    }

    @VisibleForTesting
    void triggerSendTimer() throws Exception {
        run(sendTimeout);
    }

    /**
     * Process sendTimeout events.
     */
    @Override
    public void run(Timeout timeout) throws Exception {
        if (timeout.isCancelled()) {
            return;
        }

        long timeToWaitMs;

        synchronized (this) {
            // If it's closing/closed we need to ignore this timeout and not schedule next timeout.
            if (getState() == State.Closing || getState() == State.Closed) {
                return;
            }

            OpSendMsg firstMsg = pendingMessages.peek();
            if (firstMsg == null && (batchMessageContainer == null || batchMessageContainer.isEmpty()
                    || batchMessageContainer.getFirstAddedTimestamp() == 0L)) {
                // If there are no pending messages, reset the timeout to the configured value.
                timeToWaitMs = conf.getSendTimeoutMs();
            } else {
                long createdAt;
                if (firstMsg != null) {
                    createdAt = firstMsg.createdAt;
                } else {
                    // Because we don't flush batch messages while disconnected, we consider them "createdAt" when
                    // they would have otherwise been flushed.
                    createdAt = batchMessageContainer.getFirstAddedTimestamp()
                            + TimeUnit.MICROSECONDS.toNanos(conf.getBatchingMaxPublishDelayMicros());
                }
                // If there is at least one message, calculate the diff between the message timeout and the elapsed
                // time since first message was created.
                long diff = conf.getSendTimeoutMs()
                        - TimeUnit.NANOSECONDS.toMillis(System.nanoTime() - createdAt);
                if (diff <= 0) {
                    // The diff is less than or equal to zero, meaning that the message has been timed out.
                    // Set the callback to timeout on every message, then clear the pending queue.
                    log.info("[{}] [{}] Message send timed out. Failing {} messages", topic, producerName,
                            getPendingQueueSize());
                    String msg = format("The producer %s can not send message to the topic %s within given timeout",
                            producerName, topic);
                    if (firstMsg != null) {
                        PulsarClientException te = new PulsarClientException.TimeoutException(msg, firstMsg.sequenceId);
                        failPendingMessages(cnx(), te);
                    } else {
                        failPendingBatchMessages(new PulsarClientException.TimeoutException(msg));
                    }

                    // Since the pending queue is cleared now, set timer to expire after configured value.
                    timeToWaitMs = conf.getSendTimeoutMs();
                } else {
                    // The diff is greater than zero, set the timeout to the diff value
                    timeToWaitMs = diff;
                }
            }

            sendTimeout = client.timer().newTimeout(this, timeToWaitMs, TimeUnit.MILLISECONDS);
        }
    }

    /**
     * This fails the pending messages at the start of the call, without dropping newly enqueued
     * retry messages. This method should be called from within the ProducerImpl object mutex.
     */
    @VisibleForTesting
    synchronized void failPendingMessages(ClientCnx cnx, PulsarClientException ex) {
        if (cnx == null) {
            final AtomicInteger releaseCount = new AtomicInteger();
            final boolean batchMessagingEnabled = isBatchMessagingEnabled();
            // Track message count to fail so that newly added messages by synchronous retries
            // triggered by op.sendComplete(ex); don't get removed
            int pendingMessagesToFailCount = pendingMessages.size();

            for (int i = 0; i < pendingMessagesToFailCount; i++) {
                OpSendMsg op = pendingMessages.remove();
                releaseCount.addAndGet(batchMessagingEnabled ? op.numMessagesInBatch : 1);
                try {
                    // Need to protect ourselves from any exception being thrown in the future handler from the
                    // application
                    ex.setSequenceId(op.sequenceId);
                    // if message is chunked then call callback only on last chunk
                    if (op.totalChunks <= 1 || (op.chunkId == op.totalChunks - 1)) {
                        // Need to protect ourselves from any exception being thrown in the future handler from the
                        // application
                        op.sendComplete(ex);
                    }
                } catch (Throwable t) {
                    log.warn("[{}] [{}] Got exception while completing the callback for msg {}:", topic, producerName,
                            op.sequenceId, t);
                }
                client.getMemoryLimitController().releaseMemory(op.uncompressedSize);
                ReferenceCountUtil.safeRelease(op.cmd);
                op.recycle();
            }

            semaphoreRelease(releaseCount.get());
            if (batchMessagingEnabled) {
                failPendingBatchMessages(ex);
            }

        } else {
            // If we have a connection, we schedule the callback and recycle on the event loop thread to avoid any
            // race condition since we also write the message on the socket from this thread
            cnx.ctx().channel().eventLoop().execute(() -> {
                synchronized (ProducerImpl.this) {
                    failPendingMessages(null, ex);
                }
            });
        }
    }

    /**
     * fail any pending batch messages that were enqueued, however batch was not closed out.
     *
     */
    private void failPendingBatchMessages(PulsarClientException ex) {
        if (batchMessageContainer.isEmpty()) {
            return;
        }
        final int numMessagesInBatch = batchMessageContainer.getNumMessagesInBatch();
        final long currentBatchSize = batchMessageContainer.getCurrentBatchSize();
        final int batchAllocatedSizeBytes = batchMessageContainer.getBatchAllocatedSizeBytes();
        semaphoreRelease(numMessagesInBatch);
        client.getMemoryLimitController().releaseMemory(currentBatchSize + batchAllocatedSizeBytes);
        batchMessageContainer.discard(ex);
    }

    @Override
    public CompletableFuture<Void> flushAsync() {
        synchronized (ProducerImpl.this) {
            if (isBatchMessagingEnabled()) {
                batchMessageAndSend(false);
            }
            CompletableFuture<MessageId>  lastSendFuture = this.lastSendFuture;
            if (!(lastSendFuture == this.lastSendFutureWrapper.lastSendFuture)) {
                this.lastSendFutureWrapper = LastSendFutureWrapper.create(lastSendFuture);
            }
        }

        return this.lastSendFutureWrapper.handleOnce();
    }

    @Override
    protected void triggerFlush() {
        if (isBatchMessagingEnabled()) {
            synchronized (ProducerImpl.this) {
                batchMessageAndSend(false);
            }
        }
    }

    // must acquire semaphore before calling
    private void maybeScheduleBatchFlushTask() {
        if (this.batchFlushTask != null || getState() != State.Ready) {
            return;
        }
        scheduleBatchFlushTask(conf.getBatchingMaxPublishDelayMicros());
    }

    // must acquire semaphore before calling
    private void scheduleBatchFlushTask(long batchingDelayMicros) {
        ClientCnx cnx = cnx();
        if (cnx != null && isBatchMessagingEnabled()) {
            this.batchFlushTask = cnx.ctx().executor().schedule(catchingAndLoggingThrowables(this::batchFlushTask),
                    batchingDelayMicros, TimeUnit.MICROSECONDS);
        }
    }

    private synchronized void batchFlushTask() {
        if (log.isTraceEnabled()) {
            log.trace("[{}] [{}] Batching the messages from the batch container from flush thread",
                    topic, producerName);
        }
        this.batchFlushTask = null;
        // If we're not ready, don't schedule another flush and don't try to send.
        if (getState() != State.Ready) {
            return;
        }
        // If a batch was sent more recently than the BatchingMaxPublishDelayMicros, schedule another flush to run just
        // at BatchingMaxPublishDelayMicros after the last send.
        long microsSinceLastSend = TimeUnit.NANOSECONDS.toMicros(System.nanoTime() - lastBatchSendNanoTime);
        if (microsSinceLastSend < conf.getBatchingMaxPublishDelayMicros()) {
            scheduleBatchFlushTask(conf.getBatchingMaxPublishDelayMicros() - microsSinceLastSend);
        } else if (lastBatchSendNanoTime == 0) {
            // The first time a producer sends a message, the lastBatchSendNanoTime is 0.
            lastBatchSendNanoTime = System.nanoTime();
            scheduleBatchFlushTask(conf.getBatchingMaxPublishDelayMicros());
        } else {
            batchMessageAndSend(true);
        }
    }

    // must acquire semaphore before enqueuing
    private void batchMessageAndSend(boolean shouldScheduleNextBatchFlush) {
        if (log.isTraceEnabled()) {
            log.trace("[{}] [{}] Batching the messages from the batch container with {} messages", topic, producerName,
                    batchMessageContainer.getNumMessagesInBatch());
        }
        if (!batchMessageContainer.isEmpty()) {
            try {
                lastBatchSendNanoTime = System.nanoTime();
                List<OpSendMsg> opSendMsgs;
                if (batchMessageContainer.isMultiBatches()) {
                    opSendMsgs = batchMessageContainer.createOpSendMsgs();
                } else {
                    opSendMsgs = Collections.singletonList(batchMessageContainer.createOpSendMsg());
                }
                batchMessageContainer.clear();
                for (OpSendMsg opSendMsg : opSendMsgs) {
                    processOpSendMsg(opSendMsg);
                }
            } catch (Throwable t) {
                // Since there is a uncompleted payload was built, we should reset it.
                batchMessageContainer.resetPayloadAfterFailedPublishing();
                log.warn("[{}] [{}] Failed to create batch message for sending. Batch payloads have been reset and"
                                + " messages will be retried in subsequent batches.", topic, producerName, t);
            } finally {
                if (shouldScheduleNextBatchFlush) {
                    maybeScheduleBatchFlushTask();
                }
            }
        }
    }

    protected synchronized void processOpSendMsg(OpSendMsg op) {
        if (op == null) {
            return;
        }
        try {
            if (op.msg != null && isBatchMessagingEnabled()) {
                batchMessageAndSend(false);
            }
            if (isMessageSizeExceeded(op)) {
                op.cmd.release();
                return;
            }
            final State state = getState();
            if (state == State.Terminated || state == State.Closed || state == State.ProducerFenced) {
                // The producer is in a terminal state and will never reconnect. Fail the message immediately
                // rather than leaving it stuck in pendingMessages until sendTimeout.
                releaseSemaphoreForSendOp(op);
                client.getMemoryLimitController().releaseMemory(op.uncompressedSize);
                op.sendComplete(getTerminalException(state));
                ReferenceCountUtil.safeRelease(op.cmd);
                op.recycle();
                return;
            }
            pendingMessages.add(op);
            updateLastSeqPushed(op);
            if (State.RegisteringSchema.equals(state)) {
                // Since there is a in-progress schema registration, do not continuously publish to avoid break publish
                // ordering. After the schema registration finished, it will trigger a "recoverProcessOpSendMsgFrom" to
                // publish all messages in "pendingMessages".
                return;
            }
            final ClientCnx cnx = getCnxIfReady();
            if (cnx != null) {
                if (op.msg != null && op.msg.getSchemaState() == None) {
                    tryRegisterSchema(cnx, op.msg, op.callback, this.connectionHandler.getEpoch());
                    return;
                }
                // If we do have a connection, the message is sent immediately, otherwise we'll try again once a new
                // connection is established
                op.cmd.retain();
                cnx.ctx().channel().eventLoop().execute(WriteInEventLoopCallback.create(this, cnx, op));
                stats.updateNumMsgsSent(op.numMessagesInBatch, op.batchSizeByte);
            } else {
                if (log.isDebugEnabled()) {
                    log.debug("[{}] [{}] Connection is not ready -- sequenceId {}", topic, producerName,
                        op.sequenceId);
                }
            }
        } catch (Throwable t) {
            releaseSemaphoreForSendOp(op);
            log.warn("[{}] [{}] error while closing out batch -- {}", topic, producerName, t);
            op.sendComplete(new PulsarClientException(t, op.sequenceId));
        }
    }

    protected void updateLastSeqPushed(OpSendMsg op) {
        if (op.msg != null) {
            LAST_SEQ_ID_PUSHED_UPDATER.getAndUpdate(this,
                    last -> Math.max(last, getHighestSequenceId(op)));
        }
    }

    /**
     * There are following events that will call this method.
     * 1. Republish messages in {@link #pendingMessages} after a reconnect.
     *   1-1. Using multiple version producer, and there is a message has new schema that should be registered.
     *   1-2. No message should register new schema.
     * 2. If using multiple version producer, the new schema was registered successfully.
     *   2-1. There is another message needs to register new schema,which is in {@link #pendingMessages}.
     *   2-2. {@link #pendingMessages} has no other messages that need to register new schema.
     * 3. If using multiple version producer, the new schema was failed to registered.
     *   3-1. If the new schema is incompatible.
     *     3-1-1. If {@link #pauseSendingToPreservePublishOrderOnSchemaRegFailure} is true pause all following
     *       publishing to avoid out-of-order issue.
     *     3-1-2. Otherwise, discard the failed message anc continuously publishing the following messages.
     *            Additionally, the following messages may need schema registration also.
     *   3-2. The new schema registration failed due to other error, retry registering.
     * Note: Since the current method accesses & modifies {@link #pendingMessages}, you should acquire a lock on
     *       {@link ProducerImpl} before calling method.
     */
    private void recoverProcessOpSendMsgFrom(ClientCnx cnx, MessageImpl latestMsgAttemptedRegisteredSchema,
                                             boolean failedIncompatibleSchema, long expectedEpoch) {
        if (expectedEpoch != this.connectionHandler.getEpoch() || cnx() == null) {
            // In this case, the cnx passed to this method is no longer the active connection. This method will get
            // called again once the new connection registers the producer with the broker.
            log.info("[{}][{}] Producer epoch mismatch or the current connection is null. Skip re-sending the "
                    + " {} pending messages since they will deliver using another connection.", topic,
                    producerName, pendingMessages.messagesCount());
            return;
        }
        final boolean stripChecksum = cnx.getRemoteEndpointProtocolVersion() < brokerChecksumSupportedVersion();
        Iterator<OpSendMsg> msgIterator = pendingMessages.iterator();
        MessageImpl loopStartAt = latestMsgAttemptedRegisteredSchema;
        OpSendMsg loopEndDueToSchemaRegisterNeeded = null;
        boolean pausedSendingToPreservePublishOrderOnSchemaRegFailure = false;
        while (msgIterator.hasNext()) {
            OpSendMsg op = msgIterator.next();
            if (loopStartAt != null) {
                if (op.msg == loopStartAt) {
                    loopStartAt = null;
                } else {
                    continue;
                }
            }
            if (op.msg != null) {
                if (Broken.equals(op.msg.getSchemaState())) {
                    // "Event 1-1" happens after "Event 3-1-1".
                    // Maybe user has changed the schema compatibility strategy, will retry to register the new schema.
                    if (pauseSendingToPreservePublishOrderOnSchemaRegFailure) {
                        loopEndDueToSchemaRegisterNeeded = op;
                        break;
                    } else {
                        // This scenario will never happen because the message will be removed from the queue as soon
                        // as it was set to "schemaState -> Broken".
                        SchemaInfo msgSchemaInfo = op.msg.hasReplicateFrom() ? op.msg.getSchemaInfoForReplicator()
                                : op.msg.getSchemaInfo();
                        log.error("[{}] [{}] A message attempts to register new schema, but failed. It should be"
                            + " removed from the pending queue but not, which is not expected. {}",
                            topic, producerName, SchemaUtils.jsonifySchemaInfo(msgSchemaInfo, false));
                        releaseSemaphoreForSendOp(op);
                        msgIterator.remove();
                        op.recycle();
                        continue;
                    }
                } else if (op.msg == latestMsgAttemptedRegisteredSchema && failedIncompatibleSchema
                        && op.msg.getSchemaState() == None) {
                    op.msg.setSchemaState(Broken);
                    SchemaInfo msgSchemaInfo = op.msg.hasReplicateFrom() ? op.msg.getSchemaInfoForReplicator()
                            : op.msg.getSchemaInfo();
                    // Event 3-1-1.
                    // When a schema is incompatible, we need to pause the producer to preserve message order.
                    // Otherwise, subsequent messages with compatible schemas would be delivered while this message
                    // remains stuck, causing out-of-order delivery or potential message loss with deduplication.
                    if (pauseSendingToPreservePublishOrderOnSchemaRegFailure) {
                        log.error("[{}] [{}] Publishing paused: message schema incompatible with target cluster."
                                + " To resume publishing: 1) Adjust schema compatibility strategy on target cluster"
                                + " 2) Unload topic on target cluster. Schema details: {}",
                                topic, producerName, SchemaUtils.jsonifySchemaInfo(msgSchemaInfo, false));
                        loopEndDueToSchemaRegisterNeeded = op;
                        pausedSendingToPreservePublishOrderOnSchemaRegFailure = true;
                        break;
                    }
                    // Event 3-1-2.
                    // Give user a failed callback and remove the message from "pendingMessages".
                    String failedMsg = format("[%s] [%s] incompatible schema %s", topic, producerName,
                            String.valueOf(msgSchemaInfo));
                    log.error(failedMsg);
                    // The messages' release rely on "op.cmd"'s release, we need to initialize "op.cmd" and
                    // release it to release "msg.payload".
                    if (op.cmd == null) {
                        op.rePopulate.run();
                    }
                    msgIterator.remove();
                    ReferenceCountUtil.safeRelease(op.cmd);
                    try {
                        // Need to protect ourselves from any exception being thrown in the future handler from the
                        // application
                        op.sendComplete(new IncompatibleSchemaException(failedMsg));
                    } catch (Throwable t) {
                        log.warn("Got exception while completing the failed publishing: {}", failedMsg, t);
                    }
                    releaseSemaphoreForSendOp(op);
                    op.recycle();
                    continue;
                } else if (op.msg.getSchemaState() == None) {
                    // Event 1-1.
                    // There is a message needs to register new schema when flushing pending messages after reconnected.
                    if (!rePopulateMessageSchema(op.msg)) {
                        loopEndDueToSchemaRegisterNeeded = op;
                        break;
                    }
                }
            }
            // "Event 1-2" or "Event 2-2" or "Event 3-1-2".
            if (op.cmd == null) {
                checkState(op.rePopulate != null);
                op.rePopulate.run();
                if (isMessageSizeExceeded(op)) {
                    continue;
                }
            }
            if (stripChecksum) {
                stripChecksum(op);
            }
            op.cmd.retain();
            if (log.isDebugEnabled()) {
                log.debug("[{}] [{}] Re-Sending message in cnx {}, sequenceId {}", topic, producerName,
                          cnx.channel(), op.sequenceId);
            }
            cnx.ctx().write(op.cmd, cnx.ctx().voidPromise());
            op.updateSentTimestamp();
            stats.updateNumMsgsSent(op.numMessagesInBatch, op.batchSizeByte);
        }
        cnx.ctx().flush();

        // "Event 1-1" or "Event 3-1-1" or "Event 3-1-2" or "Event 3-2".
        if (loopEndDueToSchemaRegisterNeeded != null) {
            if (compareAndSetState(State.Connecting, State.Ready)) {
                // "Event 1-1" happens after "Event 3-1-1".
                // After a topic unload, ask the producer retry to register schema, which avoids restart client
                // after users changed the compatibility strategy to make the schema is compatible.
                tryRegisterSchema(cnx, loopEndDueToSchemaRegisterNeeded.msg, loopEndDueToSchemaRegisterNeeded.callback,
                    expectedEpoch);
            } else if (pausedSendingToPreservePublishOrderOnSchemaRegFailure) {
                // Nothing to do if the event is "Event 3-1-1", just keep stuck.
                return;
            } else if (compareAndSetState(State.RegisteringSchema, State.Ready)) {
                // "Event 2-1" or "Event 3-1-2" or "Event 3-2".
                // "pendingMessages" has more messages to register new schema.
                // This operation will not be conflict with another schema registration because both operations are
                // attempt to acquire the same lock "ProducerImpl.this".
                tryRegisterSchema(cnx, loopEndDueToSchemaRegisterNeeded.msg, loopEndDueToSchemaRegisterNeeded.callback,
                        expectedEpoch);
            }
            // Schema registration will trigger a new "recoverProcessOpSendMsgFrom", so return here. If failed to switch
            // state, it means another task will trigger a new "recoverProcessOpSendMsgFrom".
            return;
        } else if (latestMsgAttemptedRegisteredSchema != null) {
            // Event 2-2 or "Event 3-1-2".
            // Switch state to "Ready" after a successful schema registration.
            compareAndSetState(State.RegisteringSchema, State.Ready);
        }
        // "Event 1-2".
        // Change state to "Ready" after reconnected.
        if (!changeToReadyState()) {
            // Producer was closed while reconnecting, close the connection to make sure the broker
            // drops the producer on its side
            cnx.channel().close();
            return;
        }
        // If any messages were enqueued while the producer was not Ready, we would have skipped
        // scheduling the batch flush task. Schedule it now, if there are messages in the batch container.
        if (isBatchMessagingEnabled() && !batchMessageContainer.isEmpty()) {
            maybeScheduleBatchFlushTask();
        }
    }

    /**
     *  Check if final message size for non-batch and non-chunked messages is larger than max message size.
     */
    private boolean isMessageSizeExceeded(OpSendMsg op) {
        if (op.msg != null && !conf.isChunkingEnabled()) {
            int messageSize = op.getMessageHeaderAndPayloadSize();
            if (messageSize > getMaxMessageSize()) {
                releaseSemaphoreForSendOp(op);
                op.sendComplete(new PulsarClientException.InvalidMessageException(
                        format("The producer %s of the topic %s sends a message with %d bytes that exceeds %d bytes",
                                producerName, topic, messageSize, getMaxMessageSize()),
                        op.sequenceId));
                return true;
            }
        }
        return false;
    }

    private int getMaxMessageSize() {
        return getConnectionHandler().getMaxMessageSize();
    }

    public long getDelayInMillis() {
        OpSendMsg firstMsg = pendingMessages.peek();
        if (firstMsg != null) {
            return TimeUnit.NANOSECONDS.toMillis(System.nanoTime() - firstMsg.createdAt);
        }
        return 0L;
    }

    public String getConnectionId() {
        return cnx() != null ? connectionId : null;
    }

    public String getConnectedSince() {
        return cnx() != null ? connectedSince : null;
    }

    public int getPendingQueueSize() {
        if (isBatchMessagingEnabled()) {
            synchronized (this) {
                return pendingMessages.messagesCount() + batchMessageContainer.getNumMessagesInBatch();
            }
        }
        return pendingMessages.messagesCount();
    }

    @Override
    public ProducerStatsRecorder getStats() {
        return stats;
    }

    @Override
    public String getProducerName() {
        return producerName;
    }

    // wrapper for connection methods
    ClientCnx cnx() {
        return this.connectionHandler.cnx();
    }

    void resetBackoff() {
        this.connectionHandler.resetBackoff();
    }

    void connectionClosed(ClientCnx cnx) {
        this.connectionHandler.connectionClosed(cnx);
    }

    public ClientCnx getClientCnx() {
        return this.connectionHandler.cnx();
    }

    void setClientCnx(ClientCnx clientCnx) {
        this.connectionHandler.setClientCnx(clientCnx);
    }

    void grabCnx() {
        this.connectionHandler.grabCnx();
    }

    @VisibleForTesting
    Optional<Semaphore> getSemaphore() {
        return semaphore;
    }

    @VisibleForTesting
    boolean isErrorStat() {
        return errorState;
    }

    @VisibleForTesting
    CompletableFuture<Void> getOriginalLastSendFuture() {
        CompletableFuture<MessageId> lastSendFuture = this.lastSendFuture;
        return lastSendFuture.thenApply(ignore -> null);
    }

    private static final Logger log = LoggerFactory.getLogger(ProducerImpl.class);
}
