RocketMQ消息消费一：消息拉取
概述
前面讲了消息在broker端的存储，下面讲消息在消费者端的消费。简单介绍几个消费相关的概念。
集群消费&广播消费
是消费者两种不同的消费模式，广播消费模式下，一个消息会被所有的机器消费。集群消费模式下，一个消息只会被同一个集群消费一次，这里的集群由ConsumerGroup相同的机器组成。
ConsumerGroup
消费者归属于一个ConsumerGroup，相同ConsumerGroup的消费者组成一个集群，一个消息只被同一个集群的机器消费一次，起到负载均衡的作用。队列的消费进度也按照ConsumerGroup进行管理，不同ConsumerGroup之间的消费进度不受影响。
消费offset
用来保存消费进度，集群模式消费进度保存在broker，广播模式保存在消费者本地。
消息消费方式
分为push和pull两种方式。pull为消费者向broker主动拉取消息，可以根据负载控制消费速度。push为broker将消息推送到消费者，可以做到消息实时推送。在RocketMQ中，push模式是通过pull模式实现的。这里以push模式的实现作为分析。
相关类
- DefaultMQPushConsumer 消费客户端
- DefaultMQPushConsumerImpl 默认push消费者实现
- RebalanceImpl 负载均衡
- MQClientInstance 客户端实例
- PullAPIWrapper 拉取消息api
- OffsetStore 消费offset存储
消费者启动
DefaultMQPushConsumer.start()为启动入口，调用DefaultMQPushConsumerImpl.start():
public synchronized void start() throws MQClientException {
switch (this.serviceState) {
case CREATE_JUST: // 默认值为CREATE_JUST
log.info("the consumer [{}] start beginning. messageModel={}, isUnitMode={}", this.defaultMQPushConsumer.getConsumerGroup(),
this.defaultMQPushConsumer.getMessageModel(), this.defaultMQPushConsumer.isUnitMode());
this.serviceState = ServiceState.START_FAILED;
// 检查相关配置
this.checkConfig();
// 复制订阅信息给RebalanceImpl负载均衡使用
this.copySubscription();
if (this.defaultMQPushConsumer.getMessageModel() == MessageModel.CLUSTERING) {
this.defaultMQPushConsumer.changeInstanceNameToPID();
}
// 创建 MQClientInstance
this.mQClientFactory = MQClientManager.getInstance().getAndCreateMQClientInstance(this.defaultMQPushConsumer, this.rpcHook);
// 负载均衡设置
this.rebalanceImpl.setConsumerGroup(this.defaultMQPushConsumer.getConsumerGroup());
this.rebalanceImpl.setMessageModel(this.defaultMQPushConsumer.getMessageModel());
this.rebalanceImpl.setAllocateMessageQueueStrategy(this.defaultMQPushConsumer.getAllocateMessageQueueStrategy());
this.rebalanceImpl.setmQClientFactory(this.mQClientFactory);
this.pullAPIWrapper = new PullAPIWrapper(
mQClientFactory,
this.defaultMQPushConsumer.getConsumerGroup(), isUnitMode());
this.pullAPIWrapper.registerFilterMessageHook(filterMessageHookList);
// OffsetStore c初始化，分为集群和广播模式
if (this.defaultMQPushConsumer.getOffsetStore() != null) {
this.offsetStore = this.defaultMQPushConsumer.getOffsetStore();
} else {
switch (this.defaultMQPushConsumer.getMessageModel()) {
case BROADCASTING:
this.offsetStore = new LocalFileOffsetStore(this.mQClientFactory, this.defaultMQPushConsumer.getConsumerGroup());
break;
case CLUSTERING:
this.offsetStore = new RemoteBrokerOffsetStore(this.mQClientFactory, this.defaultMQPushConsumer.getConsumerGroup());
break;
default:
break;
}
this.defaultMQPushConsumer.setOffsetStore(this.offsetStore);
}
this.offsetStore.load();
// consumeMessageService 消费消息服务初始化
if (this.getMessageListenerInner() instanceof MessageListenerOrderly) {
this.consumeOrderly = true;
this.consumeMessageService =
new ConsumeMessageOrderlyService(this, (MessageListenerOrderly) this.getMessageListenerInner());
} else if (this.getMessageListenerInner() instanceof MessageListenerConcurrently) {
this.consumeOrderly = false;
this.consumeMessageService =
new ConsumeMessageConcurrentlyService(this, (MessageListenerConcurrently) this.getMessageListenerInner());
}
this.consumeMessageService.start();
// 注册消费者
boolean registerOK = mQClientFactory.registerConsumer(this.defaultMQPushConsumer.getConsumerGroup(), this);
if (!registerOK) {
this.serviceState = ServiceState.CREATE_JUST;
this.consumeMessageService.shutdown();
throw new MQClientException("The consumer group[" + this.defaultMQPushConsumer.getConsumerGroup()
+ "] has been created before, specify another name please." + FAQUrl.suggestTodo(FAQUrl.GROUP_NAME_DUPLICATE_URL),
null);
}
mQClientFactory.start();
log.info("the consumer [{}] start OK.", this.defaultMQPushConsumer.getConsumerGroup());
this.serviceState = ServiceState.RUNNING;
break;
case RUNNING:
case START_FAILED:
case SHUTDOWN_ALREADY:
throw new MQClientException("The PushConsumer service state not OK, maybe started once, "
+ this.serviceState
+ FAQUrl.suggestTodo(FAQUrl.CLIENT_SERVICE_NOT_OK),
null);
default:
break;
}
// 更新订阅信息
this.updateTopicSubscribeInfoWhenSubscriptionChanged();
this.mQClientFactory.checkClientInBroker();
this.mQClientFactory.sendHeartbeatToAllBrokerWithLock();
// 立即执行负载均衡
this.mQClientFactory.rebalanceImmediately();
}
到这里启动完成。
拉取消息
拉取消息的入口在哪里呢？上面启动的时候，在MQClientInstanced.start()中启动了PullMessageService。PullMessageService继承自熟悉的ServiceThread，来看run方法：
public void run() {
while (!this.isStopped()) {
try {
// 从LinkedBlockingQueue取出请求，没有请求则阻塞
PullRequest pullRequest = this.pullRequestQueue.take();
// 执行拉取操作
this.pullMessage(pullRequest);
} catch (InterruptedException ignored) {
} catch (Exception e) {
log.error("Pull Message Service Run Method exception", e);
}
}
log.info(this.getServiceName() + " service end");
}
PullRequest放入：
- executePullRequestImmediately 立即放入，在消费者启动和拉取完成后放入
- executePullRequestLater 拉取异常情况下延迟放入
PullRequest类介绍
public class PullRequest {
// 消费组
private String consumerGroup;
// 消费队列信息
private MessageQueue messageQueue;
// 拉取到的消息存储
private ProcessQueue processQueue;
// 下次拉取offset
private long nextOffset;
}
PullMessageService拉取消息，交由DefaultMQPushConsumerImpl.pullMessage
private void pullMessage(final PullRequest pullRequest) {
final MQConsumerInner consumer = this.mQClientFactory.selectConsumer(pullRequest.getConsumerGroup());
if (consumer != null) {
// 转成 DefaultMQPushConsumerImpl，这个方法只为DefaultMQPushConsumerImpl服务，pull模式后面分析
DefaultMQPushConsumerImpl impl = (DefaultMQPushConsumerImpl) consumer;
impl.pullMessage(pullRequest);
} else {
log.warn("No matched consumer for the PullRequest {}, drop it", pullRequest);
}
}
DefaultMQPushConsumerImpl.pullMessage 拉取逻辑，交由pullAPIWrapper.pullKernelImpl
public void pullMessage(final PullRequest pullRequest) {
// 获取 消息存储队列
final ProcessQueue processQueue = pullRequest.getProcessQueue();
if (processQueue.isDropped()) {
log.info("the pull request[{}] is dropped.", pullRequest.toString());
return;
}
// 更新拉取时间戳
pullRequest.getProcessQueue().setLastPullTimestamp(System.currentTimeMillis());
try {
// 状态检查
this.makeSureStateOK();
} catch (MQClientException e) {
log.warn("pullMessage exception, consumer state not ok", e);
this.executePullRequestLater(pullRequest, PULL_TIME_DELAY_MILLS_WHEN_EXCEPTION);
return;
}
if (this.isPause()) {
log.warn("consumer was paused, execute pull request later. instanceName={}, group={}", this.defaultMQPushConsumer.getInstanceName(), this.defaultMQPushConsumer.getConsumerGroup());
this.executePullRequestLater(pullRequest, PULL_TIME_DELAY_MILLS_WHEN_SUSPEND);
return;
}
// 获取未消费消息量，流量控制
long cachedMessageCount = processQueue.getMsgCount().get();
long cachedMessageSizeInMiB = processQueue.getMsgSize().get() / (1024 * 1024);
if (cachedMessageCount > this.defaultMQPushConsumer.getPullThresholdForQueue()) {
this.executePullRequestLater(pullRequest, PULL_TIME_DELAY_MILLS_WHEN_FLOW_CONTROL);
if ((queueFlowControlTimes++ % 1000) == 0) {
log.warn(
"the cached message count exceeds the threshold {}, so do flow control, minOffset={}, maxOffset={}, count={}, size={} MiB, pullRequest={}, flowControlTimes={}",
this.defaultMQPushConsumer.getPullThresholdForQueue(), processQueue.getMsgTreeMap().firstKey(), processQueue.getMsgTreeMap().lastKey(), cachedMessageCount, cachedMessageSizeInMiB, pullRequest, queueFlowControlTimes);
}
return;
}
if (cachedMessageSizeInMiB > this.defaultMQPushConsumer.getPullThresholdSizeForQueue()) {
this.executePullRequestLater(pullRequest, PULL_TIME_DELAY_MILLS_WHEN_FLOW_CONTROL);
if ((queueFlowControlTimes++ % 1000) == 0) {
log.warn(
"the cached message size exceeds the threshold {} MiB, so do flow control, minOffset={}, maxOffset={}, count={}, size={} MiB, pullRequest={}, flowControlTimes={}",
this.defaultMQPushConsumer.getPullThresholdSizeForQueue(), processQueue.getMsgTreeMap().firstKey(), processQueue.getMsgTreeMap().lastKey(), cachedMessageCount, cachedMessageSizeInMiB, pullRequest, queueFlowControlTimes);
}
return;
}
if (!this.consumeOrderly) {
if (processQueue.getMaxSpan() > this.defaultMQPushConsumer.getConsumeConcurrentlyMaxSpan()) {
this.executePullRequestLater(pullRequest, PULL_TIME_DELAY_MILLS_WHEN_FLOW_CONTROL);
if ((queueMaxSpanFlowControlTimes++ % 1000) == 0) {
log.warn(
"the queue's messages, span too long, so do flow control, minOffset={}, maxOffset={}, maxSpan={}, pullRequest={}, flowControlTimes={}",
processQueue.getMsgTreeMap().firstKey(), processQueue.getMsgTreeMap().lastKey(), processQueue.getMaxSpan(),
pullRequest, queueMaxSpanFlowControlTimes);
}
return;
}
} else {
if (processQueue.isLocked()) {
if (!pullRequest.isLockedFirst()) {
final long offset = this.rebalanceImpl.computePullFromWhere(pullRequest.getMessageQueue());
boolean brokerBusy = offset < pullRequest.getNextOffset();
log.info("the first time to pull message, so fix offset from broker. pullRequest: {} NewOffset: {} brokerBusy: {}",
pullRequest, offset, brokerBusy);
if (brokerBusy) {
log.info("[NOTIFYME]the first time to pull message, but pull request offset larger than broker consume offset. pullRequest: {} NewOffset: {}",
pullRequest, offset);
}
pullRequest.setLockedFirst(true);
pullRequest.setNextOffset(offset);
}
} else {
this.executePullRequestLater(pullRequest, PULL_TIME_DELAY_MILLS_WHEN_EXCEPTION);
log.info("pull message later because not locked in broker, {}", pullRequest);
return;
}
}
// 获取订阅信息
final SubscriptionData subscriptionData = this.rebalanceImpl.getSubscriptionInner().get(pullRequest.getMessageQueue().getTopic());
if (null == subscriptionData) {
this.executePullRequestLater(pullRequest, PULL_TIME_DELAY_MILLS_WHEN_EXCEPTION);
log.warn("find the consumer's subscription failed, {}", pullRequest);
return;
}
final long beginTimestamp = System.currentTimeMillis();
// 注册回调函数，在消息拉取完成后调用，详见 org.apache.rocketmq.client.impl.MQClientAPIImpl.pullMessageAsync
PullCallback pullCallback = new PullCallback() {
@Override
public void onSuccess(PullResult pullResult) {
if (pullResult != null) {
// 处理拉取结果，这里主要是消息解码、消息过滤
pullResult = DefaultMQPushConsumerImpl.this.pullAPIWrapper.processPullResult(pullRequest.getMessageQueue(), pullResult,
subscriptionData);
switch (pullResult.getPullStatus()) {
case FOUND:
// 更新offset、统计信息
long prevRequestOffset = pullRequest.getNextOffset();
pullRequest.setNextOffset(pullResult.getNextBeginOffset());
long pullRT = System.currentTimeMillis() - beginTimestamp;
DefaultMQPushConsumerImpl.this.getConsumerStatsManager().incPullRT(pullRequest.getConsumerGroup(),
pullRequest.getMessageQueue().getTopic(), pullRT);
long firstMsgOffset = Long.MAX_VALUE;
// 消息拉取到，过滤后为空的情况，重新拉取
if (pullResult.getMsgFoundList() == null || pullResult.getMsgFoundList().isEmpty()) {
DefaultMQPushConsumerImpl.this.executePullRequestImmediately(pullRequest);
} else {
firstMsgOffset = pullResult.getMsgFoundList().get(0).getQueueOffset();
DefaultMQPushConsumerImpl.this.getConsumerStatsManager().incPullTPS(pullRequest.getConsumerGroup(),
pullRequest.getMessageQueue().getTopic(), pullResult.getMsgFoundList().size());
// 消息提交到 processQueue
boolean dispatchToConsume = processQueue.putMessage(pullResult.getMsgFoundList());
// 提交给 ConsumeMessageService 消费
DefaultMQPushConsumerImpl.this.consumeMessageService.submitConsumeRequest(
pullResult.getMsgFoundList(),
processQueue,
pullRequest.getMessageQueue(),
dispatchToConsume);
if (DefaultMQPushConsumerImpl.this.defaultMQPushConsumer.getPullInterval() > 0) {
DefaultMQPushConsumerImpl.this.executePullRequestLater(pullRequest,
DefaultMQPushConsumerImpl.this.defaultMQPushConsumer.getPullInterval());
} else {
DefaultMQPushConsumerImpl.this.executePullRequestImmediately(pullRequest);
}
}
if (pullResult.getNextBeginOffset() < prevRequestOffset
|| firstMsgOffset < prevRequestOffset) {
log.warn(
"[BUG] pull message result maybe data wrong, nextBeginOffset: {} firstMsgOffset: {} prevRequestOffset: {}",
pullResult.getNextBeginOffset(),
firstMsgOffset,
prevRequestOffset);
}
break;
case NO_NEW_MSG:
pullRequest.setNextOffset(pullResult.getNextBeginOffset());
DefaultMQPushConsumerImpl.this.correctTagsOffset(pullRequest);
DefaultMQPushConsumerImpl.this.executePullRequestImmediately(pullRequest);
break;
case NO_MATCHED_MSG:
pullRequest.setNextOffset(pullResult.getNextBeginOffset());
DefaultMQPushConsumerImpl.this.correctTagsOffset(pullRequest);
DefaultMQPushConsumerImpl.this.executePullRequestImmediately(pullRequest);
break;
case OFFSET_ILLEGAL:
log.warn("the pull request offset illegal, {} {}",
pullRequest.toString(), pullResult.toString());
pullRequest.setNextOffset(pullResult.getNextBeginOffset());
pullRequest.getProcessQueue().setDropped(true);
DefaultMQPushConsumerImpl.this.executeTaskLater(new Runnable() {
@Override
public void run() {
try {
DefaultMQPushConsumerImpl.this.offsetStore.updateOffset(pullRequest.getMessageQueue(),
pullRequest.getNextOffset(), false);
DefaultMQPushConsumerImpl.this.offsetStore.persist(pullRequest.getMessageQueue());
DefaultMQPushConsumerImpl.this.rebalanceImpl.removeProcessQueue(pullRequest.getMessageQueue());
log.warn("fix the pull request offset, {}", pullRequest);
} catch (Throwable e) {
log.error("executeTaskLater Exception", e);
}
}
}, 10000);
break;
default:
break;
}
}
}
@Override
public void onException(Throwable e) {
if (!pullRequest.getMessageQueue().getTopic().startsWith(MixAll.RETRY_GROUP_TOPIC_PREFIX)) {
log.warn("execute the pull request exception", e);
}
DefaultMQPushConsumerImpl.this.executePullRequestLater(pullRequest, PULL_TIME_DELAY_MILLS_WHEN_EXCEPTION);
}
};
boolean commitOffsetEnable = false;
long commitOffsetValue = 0L;
if (MessageModel.CLUSTERING == this.defaultMQPushConsumer.getMessageModel()) {
commitOffsetValue = this.offsetStore.readOffset(pullRequest.getMessageQueue(), ReadOffsetType.READ_FROM_MEMORY);
if (commitOffsetValue > 0) {
commitOffsetEnable = true;
}
}
String subExpression = null;
boolean classFilter = false;
SubscriptionData sd = this.rebalanceImpl.getSubscriptionInner().get(pullRequest.getMessageQueue().getTopic());
if (sd != null) {
if (this.defaultMQPushConsumer.isPostSubscriptionWhenPull() && !sd.isClassFilterMode()) {
subExpression = sd.getSubString();
}
classFilter = sd.isClassFilterMode();
}
int sysFlag = PullSysFlag.buildSysFlag(
commitOffsetEnable, // commitOffset
true, // suspend
subExpression != null, // subscription
classFilter // class filter
);
try {
// 调用 pullKernelImpl 拉取消息
this.pullAPIWrapper.pullKernelImpl(
pullRequest.getMessageQueue(),
subExpression,
subscriptionData.getExpressionType(),
subscriptionData.getSubVersion(),
pullRequest.getNextOffset(),
this.defaultMQPushConsumer.getPullBatchSize(),
sysFlag,
commitOffsetValue,
BROKER_SUSPEND_MAX_TIME_MILLIS,
CONSUMER_TIMEOUT_MILLIS_WHEN_SUSPEND,
CommunicationMode.ASYNC, // 异步
pullCallback
);
} catch (Exception e) {
log.error("pullKernelImpl exception", e);
this.executePullRequestLater(pullRequest, PULL_TIME_DELAY_MILLS_WHEN_EXCEPTION);
}
}
PullAPIWrapper.pullKernelImpl， 主要功能：校验broker信息、构造netty请求消息头。之后将拉取请求委托到MQClientAPIImpl.pullMessage()
public PullResult pullKernelImpl(
final MessageQueue mq,
final String subExpression,
final String expressionType,
final long subVersion,
final long offset,
final int maxNums,
final int sysFlag,
final long commitOffset,
final long brokerSuspendMaxTimeMillis,
final long timeoutMillis,
final CommunicationMode communicationMode,
final PullCallback pullCallback
) throws MQClientException, RemotingException, MQBrokerException, InterruptedException {
FindBrokerResult findBrokerResult =
this.mQClientFactory.findBrokerAddressInSubscribe(mq.getBrokerName(),
this.recalculatePullFromWhichNode(mq), false);
// broker信息为空，更新后重新获取
if (null == findBrokerResult) {
this.mQClientFactory.updateTopicRouteInfoFromNameServer(mq.getTopic());
findBrokerResult =
this.mQClientFactory.findBrokerAddressInSubscribe(mq.getBrokerName(),
this.recalculatePullFromWhichNode(mq), false);
}
if (findBrokerResult != null) {
{
// check version
if (!ExpressionType.isTagType(expressionType)
&& findBrokerResult.getBrokerVersion() < MQVersion.Version.V4_1_0_SNAPSHOT.ordinal()) {
throw new MQClientException("The broker[" + mq.getBrokerName() + ", "
+ findBrokerResult.getBrokerVersion() + "] does not upgrade to support for filter message by " + expressionType, null);
}
}
int sysFlagInner = sysFlag;
if (findBrokerResult.isSlave()) {
sysFlagInner = PullSysFlag.clearCommitOffsetFlag(sysFlagInner);
}
// 构造netty请求拉取消息协议头
PullMessageRequestHeader requestHeader = new PullMessageRequestHeader();
requestHeader.setConsumerGroup(this.consumerGroup);
requestHeader.setTopic(mq.getTopic());
requestHeader.setQueueId(mq.getQueueId());
requestHeader.setQueueOffset(offset);
requestHeader.setMaxMsgNums(maxNums);
requestHeader.setSysFlag(sysFlagInner);
requestHeader.setCommitOffset(commitOffset);
requestHeader.setSuspendTimeoutMillis(brokerSuspendMaxTimeMillis);
requestHeader.setSubscription(subExpression);
requestHeader.setSubVersion(subVersion);
requestHeader.setExpressionType(expressionType);
String brokerAddr = findBrokerResult.getBrokerAddr();
if (PullSysFlag.hasClassFilterFlag(sysFlagInner)) {
brokerAddr = computPullFromWhichFilterServer(mq.getTopic(), brokerAddr);
}
// 委托到 MQClientAPIImpl.pullMessage()
PullResult pullResult = this.mQClientFactory.getMQClientAPIImpl().pullMessage(
brokerAddr,
requestHeader,
timeoutMillis,
communicationMode,
pullCallback);
return pullResult;
}
throw new MQClientException("The broker[" + mq.getBrokerName() + "] not exist", null);
}
分为同步和异步两种模式，异步会调用之前注册的pullCallback回调函数。
public PullResult pullMessage(
final String addr,
final PullMessageRequestHeader requestHeader,
final long timeoutMillis,
final CommunicationMode communicationMode,
final PullCallback pullCallback
) throws RemotingException, MQBrokerException, InterruptedException {
RemotingCommand request = RemotingCommand.createRequestCommand(RequestCode.PULL_MESSAGE, requestHeader);
switch (communicationMode) {
case ONEWAY:
assert false;
return null;
case ASYNC:
this.pullMessageAsync(addr, request, timeoutMillis, pullCallback);
return null;
case SYNC:
return this.pullMessageSync(addr, request, timeoutMillis);
default:
assert false;
break;
}
return null;
}
// 异步
private void pullMessageAsync(
final String addr,
final RemotingCommand request,
final long timeoutMillis,
final PullCallback pullCallback
) throws RemotingException, InterruptedException {
this.remotingClient.invokeAsync(addr, request, timeoutMillis, new InvokeCallback() {
@Override
public void operationComplete(ResponseFuture responseFuture) {
RemotingCommand response = responseFuture.getResponseCommand();
if (response != null) {
try {
// 根据response构造pullResult
PullResult pullResult = MQClientAPIImpl.this.processPullResponse(response);
assert pullResult != null;
// 执行拉取回调函数逻辑
pullCallback.onSuccess(pullResult);
} catch (Exception e) {
pullCallback.onException(e);
}
} else {
if (!responseFuture.isSendRequestOK()) {
pullCallback.onException(new MQClientException("send request failed to " + addr + ". Request: " + request, responseFuture.getCause()));
} else if (responseFuture.isTimeout()) {
pullCallback.onException(new MQClientException("wait response from " + addr + " timeout :" + responseFuture.getTimeoutMillis() + "ms" + ". Request: " + request,
responseFuture.getCause()));
} else {
pullCallback.onException(new MQClientException("unknown reason. addr: " + addr + ", timeoutMillis: " + timeoutMillis + ". Request: " + request, responseFuture.getCause()));
}
}
}
});
}
// 同步
private PullResult pullMessageSync(
final String addr,
final RemotingCommand request,
final long timeoutMillis
) throws RemotingException, InterruptedException, MQBrokerException {
RemotingCommand response = this.remotingClient.invokeSync(addr, request, timeoutMillis);
assert response != null;
return this.processPullResponse(response);
}
消费消息
消费消息在回调函数中执行，具体为将消息提交到ConsumeMessageService，ConsumeMessageService有两个子类ConsumeMessageConcurrentlyService和ConsumeMessageOrderlyService，这里以ConsumeMessageConcurrentlyService为例介绍。入口为submitConsumeRequest()
public void submitConsumeRequest(
final List<MessageExt> msgs,
final ProcessQueue processQueue,
final MessageQueue messageQueue,
final boolean dispatchToConsume) {
final int consumeBatchSize = this.defaultMQPushConsumer.getConsumeMessageBatchMaxSize();
if (msgs.size() <= consumeBatchSize) {
// 构造消费请求
ConsumeRequest consumeRequest = new ConsumeRequest(msgs, processQueue, messageQueue);
try {
this.consumeExecutor.submit(consumeRequest);
} catch (RejectedExecutionException e) {
this.submitConsumeRequestLater(consumeRequest);
}
} else {
// 消息数量超过单次消费限制，分批处理
for (int total = 0; total < msgs.size(); ) {
List<MessageExt> msgThis = new ArrayList<MessageExt>(consumeBatchSize);
for (int i = 0; i < consumeBatchSize; i++, total++) {
if (total < msgs.size()) {
msgThis.add(msgs.get(total));
} else {
break;
}
}
ConsumeRequest consumeRequest = new ConsumeRequest(msgThis, processQueue, messageQueue);
try {
this.consumeExecutor.submit(consumeRequest);
} catch (RejectedExecutionException e) {
for (; total < msgs.size(); total++) {
msgThis.add(msgs.get(total));
}
this.submitConsumeRequestLater(consumeRequest);
}
}
}
}
主要消费逻辑还是在ConsumeRequest，ConsumeRequest实现了Runnable接口，具体看run()方法：
public void run() {
if (this.processQueue.isDropped()) {
// 状态检查
log.info("the message queue not be able to consume, because it's dropped. group={} {}", ConsumeMessageConcurrentlyService.this.consumerGroup, this.messageQueue);
return;
}
// listener 为具体实现消费消息逻辑的地方
MessageListenerConcurrently listener = ConsumeMessageConcurrentlyService.this.messageListener;
ConsumeConcurrentlyContext context = new ConsumeConcurrentlyContext(messageQueue);
ConsumeConcurrentlyStatus status = null;
defaultMQPushConsumerImpl.resetRetryAndNamespace(msgs, defaultMQPushConsumer.getConsumerGroup());
ConsumeMessageContext consumeMessageContext = null;
// 前置hook
if (ConsumeMessageConcurrentlyService.this.defaultMQPushConsumerImpl.hasHook()) {
consumeMessageContext = new ConsumeMessageContext();
consumeMessageContext.setNamespace(defaultMQPushConsumer.getNamespace());
consumeMessageContext.setConsumerGroup(defaultMQPushConsumer.getConsumerGroup());
consumeMessageContext.setProps(new HashMap<String, String>());
consumeMessageContext.setMq(messageQueue);
consumeMessageContext.setMsgList(msgs);
consumeMessageContext.setSuccess(false);
ConsumeMessageConcurrentlyService.this.defaultMQPushConsumerImpl.executeHookBefore(consumeMessageContext);
}
long beginTimestamp = System.currentTimeMillis();
boolean hasException = false;
ConsumeReturnType returnType = ConsumeReturnType.SUCCESS;
try {
if (msgs != null && !msgs.isEmpty()) {
for (MessageExt msg : msgs) {
MessageAccessor.setConsumeStartTimeStamp(msg, String.valueOf(System.currentTimeMillis()));
}
}
// 调用 listener 消费消息
status = listener.consumeMessage(Collections.unmodifiableList(msgs), context);
} catch (Throwable e) {
log.warn("consumeMessage exception: {} Group: {} Msgs: {} MQ: {}",
RemotingHelper.exceptionSimpleDesc(e),
ConsumeMessageConcurrentlyService.this.consumerGroup,
msgs,
messageQueue);
hasException = true;
}
long consumeRT = System.currentTimeMillis() - beginTimestamp;
// 消费状态处理
if (null == status) {
if (hasException) {
returnType = ConsumeReturnType.EXCEPTION;
} else {
returnType = ConsumeReturnType.RETURNNULL;
}
} else if (consumeRT >= defaultMQPushConsumer.getConsumeTimeout() * 60 * 1000) {
returnType = ConsumeReturnType.TIME_OUT;
} else if (ConsumeConcurrentlyStatus.RECONSUME_LATER == status) {
returnType = ConsumeReturnType.FAILED;
} else if (ConsumeConcurrentlyStatus.CONSUME_SUCCESS == status) {
returnType = ConsumeReturnType.SUCCESS;
}
if (ConsumeMessageConcurrentlyService.this.defaultMQPushConsumerImpl.hasHook()) {
consumeMessageContext.getProps().put(MixAll.CONSUME_CONTEXT_TYPE, returnType.name());
}
if (null == status) {
log.warn("consumeMessage return null, Group: {} Msgs: {} MQ: {}",
ConsumeMessageConcurrentlyService.this.consumerGroup,
msgs,
messageQueue);
status = ConsumeConcurrentlyStatus.RECONSUME_LATER;
}
// 消费后置hook
if (ConsumeMessageConcurrentlyService.this.defaultMQPushConsumerImpl.hasHook()) {
consumeMessageContext.setStatus(status.toString());
consumeMessageContext.setSuccess(ConsumeConcurrentlyStatus.CONSUME_SUCCESS == status);
ConsumeMessageConcurrentlyService.this.defaultMQPushConsumerImpl.executeHookAfter(consumeMessageContext);
}
ConsumeMessageConcurrentlyService.this.getConsumerStatsManager()
.incConsumeRT(ConsumeMessageConcurrentlyService.this.consumerGroup, messageQueue.getTopic(), consumeRT);
if (!processQueue.isDropped()) {
// 处理消息消费结果
ConsumeMessageConcurrentlyService.this.processConsumeResult(status, context, this);
} else {
log.warn("processQueue is dropped without process consume result. messageQueue={}, msgs={}", messageQueue, msgs);
}
}
public MessageQueue getMessageQueue() {
return messageQueue;
}
}
processConsumeResult()对消费结果做处理：成功则从从ProcessQueue中移除消息，失败则将消息发送到broker重新消费。
public void processConsumeResult(
final ConsumeConcurrentlyStatus status,
final ConsumeConcurrentlyContext context,
final ConsumeRequest consumeRequest
) {
int ackIndex = context.getAckIndex();
if (consumeRequest.getMsgs().isEmpty())
return;
switch (status) {
// 消费成功
case CONSUME_SUCCESS:
if (ackIndex >= consumeRequest.getMsgs().size()) {
ackIndex = consumeRequest.getMsgs().size() - 1;
}
int ok = ackIndex + 1;
int failed = consumeRequest.getMsgs().size() - ok;
this.getConsumerStatsManager().incConsumeOKTPS(consumerGroup, consumeRequest.getMessageQueue().getTopic(), ok);
this.getConsumerStatsManager().incConsumeFailedTPS(consumerGroup, consumeRequest.getMessageQueue().getTopic(), failed);
break;
// 消费失败，需重试
case RECONSUME_LATER:
ackIndex = -1;
this.getConsumerStatsManager().incConsumeFailedTPS(consumerGroup, consumeRequest.getMessageQueue().getTopic(),
consumeRequest.getMsgs().size());
break;
default:
break;
}
switch (this.defaultMQPushConsumer.getMessageModel()) {
case BROADCASTING:
for (int i = ackIndex + 1; i < consumeRequest.getMsgs().size(); i++) {
MessageExt msg = consumeRequest.getMsgs().get(i);
log.warn("BROADCASTING, the message consume failed, drop it, {}", msg.toString());
}
break;
case CLUSTERING:
List<MessageExt> msgBackFailed = new ArrayList<MessageExt>(consumeRequest.getMsgs().size());
for (int i = ackIndex + 1; i < consumeRequest.getMsgs().size(); i++) {
MessageExt msg = consumeRequest.getMsgs().get(i);
// 消费失败消息发送到broker重新消费
boolean result = this.sendMessageBack(msg, context);
if (!result) {
msg.setReconsumeTimes(msg.getReconsumeTimes() + 1);
msgBackFailed.add(msg);
}
}
if (!msgBackFailed.isEmpty()) {
consumeRequest.getMsgs().removeAll(msgBackFailed);
this.submitConsumeRequestLater(msgBackFailed, consumeRequest.getProcessQueue(), consumeRequest.getMessageQueue());
}
break;
default:
break;
}
// 从ProcessQueue 中移除已经消费完成的消息
long offset = consumeRequest.getProcessQueue().removeMessage(consumeRequest.getMsgs());
if (offset >= 0 && !consumeRequest.getProcessQueue().isDropped()) {
this.defaultMQPushConsumerImpl.getOffsetStore().updateOffset(consumeRequest.getMessageQueue(), offset, true);
}
}
下面看流程图：
