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源码版本
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官方提供的Consumer消费消息的demo代码
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客户端消息的拉取
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带注释的源码地址
源码版本
4.8.0
官方提供的Consumer消费消息的demo代码
DefaultMQPushConsumer consumer = new DefaultMQPushConsumer("please_rename_unique_group_name_4");
// 1. 设置 NamesrvAddr 地址
consumer.setNamesrvAddr("127.0.0.1:9876");
// 2. 设置消费位点 可选值参考枚举 ConsumeFromWhere
consumer.setConsumeFromWhere(ConsumeFromWhere.CONSUME_FROM_FIRST_OFFSET);
// 3. 设置订阅topic
consumer.subscribe("TopicTest", "*");
// 4. 设置消费消息业务逻辑
consumer.registerMessageListener(new MessageListenerConcurrently() {
@Override
public ConsumeConcurrentlyStatus consumeMessage(List<MessageExt> msgs,
ConsumeConcurrentlyContext context) {
System.out.printf("%s Receive New Messages: %s %n", Thread.currentThread().getName(), msgs);
return ConsumeConcurrentlyStatus.CONSUME_SUCCESS;
}
});
// 5. 消费者启动
consumer.start();
可以看到这就是消费消息最简单的一个使用，我们来具体分析一下源码
1 2 3 4 目前都是设置一些消费者(DefaultMQPushConsumer)的属性，我们先不去具体分析,在后面实际使用的时候再去分析 ,我们直接从5消费者启动开始
@Override
public void start() throws MQClientException {
// 1.设置消费者groupID
setConsumerGroup(NamespaceUtil.wrapNamespace(this.getNamespace(), this.consumerGroup));
// 2.消费者启动
this.defaultMQPushConsumerImpl.start();
if (null != traceDispatcher) {
try {
traceDispatcher.start(this.getNamesrvAddr(), this.getAccessChannel());
} catch (MQClientException e) {
log.warn("trace dispatcher start failed ", e);
}
}
}
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设置消费者groupID -
消费者启动，我们进入到 defaultMQPushConsumerImpl.start();方法
public synchronized void start() throws MQClientException {
switch (this.serviceState) {
// 消费者刚刚创建，未启动
case CREATE_JUST:
log.info("the consumer [{}] start beginning. messageModel={}, isUnitMode={}", this.defaultMQPushConsumer.getConsumerGroup(),
this.defaultMQPushConsumer.getMessageModel(), this.defaultMQPushConsumer.isUnitMode());
this.serviceState = ServiceState.START_FAILED;
// 1. 检查配置参数
this.checkConfig();
/**
* 2. 根据topic 获取订阅消息
* 将DefaultMQPushConsumer的订阅信息copy到RebalanceService中
*/
this.copySubscription();
// 3. 集群模式将进程id设置为消费者实例名 否则使用pid
if (this.defaultMQPushConsumer.getMessageModel() == MessageModel.CLUSTERING) {
this.defaultMQPushConsumer.changeInstanceNameToPID();
}
// 4. 创建mqClient 缓存客户端和topic信息，各种service 一个进程只有一个实例
this.mQClientFactory = MQClientManager.getInstance().getOrCreateMQClientInstance(this.defaultMQPushConsumer, this.rpcHook);
// 5. 设置消费者组
this.rebalanceImpl.setConsumerGroup(this.defaultMQPushConsumer.getConsumerGroup());
// 6. 设置消费模式 分集群模式和广播模式
this.rebalanceImpl.setMessageModel(this.defaultMQPushConsumer.getMessageModel());
// 7. 设置负载均衡算法 默认avg
this.rebalanceImpl.setAllocateMessageQueueStrategy(this.defaultMQPushConsumer.getAllocateMessageQueueStrategy());
// 8. 设置mq客户端
this.rebalanceImpl.setmQClientFactory(this.mQClientFactory);
// 9. PullRequest封装实现类，封装了和broker的通信接口 后续从Broker拉取消息会用到
this.pullAPIWrapper = new PullAPIWrapper(
mQClientFactory,
this.defaultMQPushConsumer.getConsumerGroup(), isUnitMode());
// 10. 设置消息被客户端过滤调用的钩子函数
this.pullAPIWrapper.registerFilterMessageHook(filterMessageHookList);
// 11. 设置 消息消费进度存储器
if (this.defaultMQPushConsumer.getOffsetStore() != null) {
this.offsetStore = this.defaultMQPushConsumer.getOffsetStore();
} else {
switch (this.defaultMQPushConsumer.getMessageModel()) {
// 广播模式本地持久化消息消费进度存储器
case BROADCASTING:
this.offsetStore = new LocalFileOffsetStore(this.mQClientFactory, this.defaultMQPushConsumer.getConsumerGroup());
break;
// 集群模式持久化消息消费进度存储器
case CLUSTERING:
this.offsetStore = new RemoteBrokerOffsetStore(this.mQClientFactory, this.defaultMQPushConsumer.getConsumerGroup());
break;
default:
break;
}
// 设置集群模式持久化消息消费进度存储器
this.defaultMQPushConsumer.setOffsetStore(this.offsetStore);
}
// 12. 加载消费进度 分远程和本地，本地通过文件加载
this.offsetStore.load();
// 13. 构建消费服务 consumeMessageService接口有两个实现类: MessageListenerOrderly 处理顺序消费, MessageListenerConcurrently 处理并发消费
if (this.getMessageListenerInner() instanceof MessageListenerOrderly) {
this.consumeOrderly = true;
this.consumeMessageService =
new ConsumeMessageOrderlyService(this, (MessageListenerOrderly) this.getMessageListenerInner());
} else if (this.getMessageListenerInner() instanceof MessageListenerConcurrently) { // 异步消息 并发消费
this.consumeOrderly = false;
this.consumeMessageService =
new ConsumeMessageConcurrentlyService(this, (MessageListenerConcurrently) this.getMessageListenerInner());
}
// 14. 启动了清理等待处理消息线程
this.consumeMessageService.start();
// 15. 注册（缓存）consumer，保证CID单例
boolean registerOK = mQClientFactory.registerConsumer(this.defaultMQPushConsumer.getConsumerGroup(), this);
if (!registerOK) {
this.serviceState = ServiceState.CREATE_JUST;
this.consumeMessageService.shutdown(defaultMQPushConsumer.getAwaitTerminationMillisWhenShutdown());
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);
}
/**
* 16. 启动MQClientInstance 消费者拉取消息核心方法
* 会启动 PullMessageService 线程和 RebalanceService 线程
*/
mQClientFactory.start();
log.info("the consumer [{}] start OK.", this.defaultMQPushConsumer.getConsumerGroup());
// 17. 设置消费client状态为 运行状态
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;
}
// 从NameServer更新topic路由和订阅信息
this.updateTopicSubscribeInfoWhenSubscriptionChanged();
this.mQClientFactory.checkClientInBroker();
// 发送心跳，同步consumer配置到broker,同步FilterClass到FilterServer(PushConsumer)
this.mQClientFactory.sendHeartbeatToAllBrokerWithLock();
this.mQClientFactory.rebalanceImmediately();
}
上面代码都有详细注释,这里再详细分析一下
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首先检查客户端状态
private volatile ServiceState serviceState = ServiceState.CREATE_JUST;
可以看到初始状态就是CREATE_JUST 就进入到 case CREATE_JUST 代码块中，如果是 RUNNING 、START_FAILED 、SHUTDOWN_ALREADY 状态就抛出异常
我们现在来分析下 case CREATE_JUST 中的代码
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首先将client状态设置为 启动失败状态: START_FAILED -
检测配置参数，如果有配置为空或者配置错误则抛异常 -
根据topic 获取订阅消息
this.copySubscription();
private void copySubscription() throws MQClientException {
try {
/**
* key : topic
* value: sub expression
* 取出订阅关系表
*/
Map<String, String> sub = this.defaultMQPushConsumer.getSubscription();
if (sub != null) {
for (final Map.Entry<String, String> entry : sub.entrySet()) {
final String topic = entry.getKey();
final String subString = entry.getValue();
// 构建 SubscriptionData 主要是包括订阅的一些属性 比如
SubscriptionData subscriptionData = FilterAPI.buildSubscriptionData(this.defaultMQPushConsumer.getConsumerGroup(),
topic, subString);
// 把组装好的订阅关系保存到 rebalanceImpl 中
this.rebalanceImpl.getSubscriptionInner().put(topic, subscriptionData);
}
}
// 注册监听器
if (null == this.messageListenerInner) {
this.messageListenerInner = this.defaultMQPushConsumer.getMessageListener();
}
switch (this.defaultMQPushConsumer.getMessageModel()) {
case BROADCASTING:
break;
case CLUSTERING:
/**
* 如果是集群模式，则将重试topic也加入到subscriptionInner中，
* 消息重试是以消费组为单位，topic为 %RETRY% + 消费组名
*/
final String retryTopic = MixAll.getRetryTopic(this.defaultMQPushConsumer.getConsumerGroup());
SubscriptionData subscriptionData = FilterAPI.buildSubscriptionData(this.defaultMQPushConsumer.getConsumerGroup(),
retryTopic, SubscriptionData.SUB_ALL);
this.rebalanceImpl.getSubscriptionInner().put(retryTopic, subscriptionData);
break;
default:
break;
}
} catch (Exception e) {
throw new MQClientException("subscription exception", e);
}
}
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集群模式将进程id设置为消费者实例名 否则使用pid
public void changeInstanceNameToPID() {
if (this.instanceName.equals("DEFAULT")) {
this.instanceName = String.valueOf(UtilAll.getPid());
}
}
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创建 mqClient 缓存客户端和topic信息，各种service 一个进程只有一个实例，我们进入 getOrCreateMQClientInstance方法看看
private ConcurrentMap<String/* clientId */, MQClientInstance> factoryTable =
new ConcurrentHashMap<String, MQClientInstance>();
public MQClientInstance getOrCreateMQClientInstance(final ClientConfig clientConfig, RPCHook rpcHook) {
String clientId = clientConfig.buildMQClientId();
MQClientInstance instance = this.factoryTable.get(clientId);
if (null == instance) {
instance =
new MQClientInstance(clientConfig.cloneClientConfig(),
this.factoryIndexGenerator.getAndIncrement(), clientId, rpcHook);
MQClientInstance prev = this.factoryTable.putIfAbsent(clientId, instance);
if (prev != null) {
instance = prev;
log.warn("Returned Previous MQClientInstance for clientId:[{}]", clientId);
} else {
log.info("Created new MQClientInstance for clientId:[{}]", clientId);
}
}
return instance;
}
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设置消费者组 -
设置消费模式 分集群模式和广播模式 -
设置负载均衡算法 默认avg -
设置mq客户端 -
PullRequest封装实现类，封装了和broker的通信接口 后续从Broker拉取消息会用到 -
设置消息被客户端过滤调用的钩子函数 -
设置 消息消费进度存储器 -
加载消费进度 分远程和本地，本地通过文件加载 目前远程实现类是个空方法，只有本地加载有具体实现方法，我们看看 LocalFileOffsetStore中load的实现
//以MessageQueue为键-消费偏移量为值的缓存表
private ConcurrentMap<MessageQueue, AtomicLong> offsetTable = new ConcurrentHashMap<MessageQueue, AtomicLong>();
public void load() throws MQClientException {
//从本地磁盘中进行读取json文件-并进行序列化封装转化为map
OffsetSerializeWrapper offsetSerializeWrapper = this.readLocalOffset();
if (offsetSerializeWrapper != null && offsetSerializeWrapper.getOffsetTable() != null) {
//存入缓存表
offsetTable.putAll(offsetSerializeWrapper.getOffsetTable());
for (MessageQueue mq : offsetSerializeWrapper.getOffsetTable().keySet()) {
AtomicLong offset = offsetSerializeWrapper.getOffsetTable().get(mq);
log.info("load consumer's offset, {} {} {}",
this.groupName,
mq,
offset.get());
}
}
}
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构建消费服务 consumeMessageService接口有两个实现类: MessageListenerOrderly 处理顺序消费, MessageListenerConcurrently 处理并发消费 -
启动清理过期消息的线程 消息过期时间为15分钟,15分钟清理一次,延迟15分钟启动,我们这里看看 ConsumeMessageConcurrentlyService中的start方法
public void start() {
this.cleanExpireMsgExecutors.scheduleAtFixedRate(new Runnable() {
@Override
public void run() {
// 清理异常消息
cleanExpireMsg();
}
}, this.defaultMQPushConsumer.getConsumeTimeout(), this.defaultMQPushConsumer.getConsumeTimeout(), TimeUnit.MINUTES);
}
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注册（缓存）consumer，保证CID单例， mQClientFactory是我们5步创建的，我们看看registerConsumer方法
private final ConcurrentMap<String/* group */, MQConsumerInner> consumerTable = new ConcurrentHashMap<String, MQConsumerInner>();
public boolean registerConsumer(final String group, final MQConsumerInner consumer) {
if (null == group || null == consumer) {
return false;
}
MQConsumerInner prev = this.consumerTable.putIfAbsent(group, consumer);
if (prev != null) {
log.warn("the consumer group[" + group + "] exist already.");
return false;
}
return true;
}
可以看到只是将 consumer 放入consumerTable 中，没有向nameServer 注册
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启动MQClientInstance 消费者拉取消息核心方法 ，会启动 PullMessageService 线程和 RebalanceService 线程，我们进入 mQClientFactory的start方法
public void start() throws MQClientException {
synchronized (this) {
switch (this.serviceState) {
case CREATE_JUST:
this.serviceState = ServiceState.START_FAILED;
// If not specified,looking address from name server
// 1. 获取 namesrvAddr 地址
if (null == this.clientConfig.getNamesrvAddr()) {
this.mQClientAPIImpl.fetchNameServerAddr();
}
/**
* 2. Start request-response channel netty相关网络请求封装
* 启动一个netty客户端
*/
this.mQClientAPIImpl.start();
// 3. Start various schedule tasks 启动一些定时器
this.startScheduledTask();
// 4. Start pull service
/**
* 核心方法 开启拉取消息线程, 方法逻辑在本类的 run 方法 @{link PullMessageService run 方法}
*/
this.pullMessageService.start();
// 5. Start rebalance service
this.rebalanceService.start();
// 6. Start push service 发送要求重新的消息
this.defaultMQProducer.getDefaultMQProducerImpl().start(false);
log.info("the client factory [{}] start OK", this.clientId);
// 7. 将 serviceState 状态设置为运行状态
this.serviceState = ServiceState.RUNNING;
break;
case START_FAILED:
throw new MQClientException("The Factory object[" + this.getClientId() + "] has been created before, and failed.", null);
default:
break;
}
}
}
上面的注释比较详细了，我们分析一下3启动了哪些定时器
private void startScheduledTask() {
// 每隔2分钟尝试获取一次NameServer地址
if (null == this.clientConfig.getNamesrvAddr()) {
this.scheduledExecutorService.scheduleAtFixedRate(new Runnable() {
@Override
public void run() {
try {
MQClientInstance.this.mQClientAPIImpl.fetchNameServerAddr();
} catch (Exception e) {
log.error("ScheduledTask fetchNameServerAddr exception", e);
}
}
}, 1000 * 10, 1000 * 60 * 2, TimeUnit.MILLISECONDS);
}
// 默认每隔30S尝试更新主题路由信息
this.scheduledExecutorService.scheduleAtFixedRate(new Runnable() {
@Override
public void run() {
try {
MQClientInstance.this.updateTopicRouteInfoFromNameServer();
} catch (Exception e) {
log.error("ScheduledTask updateTopicRouteInfoFromNameServer exception", e);
}
}
}, 10, this.clientConfig.getPollNameServerInterval(), TimeUnit.MILLISECONDS);
// 每隔30S 进行Broker心跳检测
this.scheduledExecutorService.scheduleAtFixedRate(new Runnable() {
@Override
public void run() {
try {
MQClientInstance.this.cleanOfflineBroker();
MQClientInstance.this.sendHeartbeatToAllBrokerWithLock();
} catch (Exception e) {
log.error("ScheduledTask sendHeartbeatToAllBroker exception", e);
}
}
}, 1000, this.clientConfig.getHeartbeatBrokerInterval(), TimeUnit.MILLISECONDS);
// //默认每隔5秒持久化ConsumeOffset
this.scheduledExecutorService.scheduleAtFixedRate(new Runnable() {
@Override
public void run() {
try {
MQClientInstance.this.persistAllConsumerOffset();
} catch (Exception e) {
log.error("ScheduledTask persistAllConsumerOffset exception", e);
}
}
}, 1000 * 10, this.clientConfig.getPersistConsumerOffsetInterval(), TimeUnit.MILLISECONDS);
//默认每隔1S检查线程池适配
this.scheduledExecutorService.scheduleAtFixedRate(new Runnable() {
@Override
public void run() {
try {
MQClientInstance.this.adjustThreadPool();
} catch (Exception e) {
log.error("ScheduledTask adjustThreadPool exception", e);
}
}
}, 1, 1, TimeUnit.MINUTES);
}
然后我们再回来重点分析一下拉取消息的方法
// 启动线程 线程的run方法实现在 PullMessageService 中
this.pullMessageService.start();
private final LinkedBlockingQueue<PullRequest> pullRequestQueue = new LinkedBlockingQueue<PullRequest>();
public void run() {
log.info(this.getServiceName() + " service started");
while (!this.isStopped()) {
try {
// 从LinkedBlockingQueue中拉取 pullRequest 如果队列为空 则阻塞等待
PullRequest pullRequest = this.pullRequestQueue.take();
this.pullMessage(pullRequest);
} catch (InterruptedException ignored) {
} catch (Exception e) {
log.error("Pull Message Service Run Method exception", e);
}
}
log.info(this.getServiceName() + " service end");
}
可以看到主要是从pullRequestQueue 中获取PullRequest 然后去消费消息。所以可以确定的是什么地方向pullRequestQueue put值就是真正的消息拉取的实现
然后我们重点看看 pullRequestQueue 这个队列是如何放入数据到里面的，查看调用链发现主要是如下方法调用
PullRequest pullRequest = this.pullRequestQueue.take();
可以看到有两个地方，我们一起来看看这两个方法
// DefaultMQPushConsumerImpl.class
public void executePullRequestImmediately(final PullRequest pullRequest) {
this.mQClientFactory.getPullMessageService().executePullRequestImmediately(pullRequest);
}
// PullMessageService.class
public void executePullRequestLater(final PullRequest pullRequest, final long timeDelay) {
if (!isStopped()) {
this.scheduledExecutorService.schedule(new Runnable() {
@Override
public void run() {
PullMessageService.this.executePullRequestImmediately(pullRequest);
}
}, timeDelay, TimeUnit.MILLISECONDS);
} else {
log.warn("PullMessageServiceScheduledThread has shutdown");
}
}
可以看到executePullRequestImmediately 方法是立即放入pullRequest,executePullRequestLater 方法是延迟放入pullRequest，什么时候需要延迟放入pullRequest 呢，都是出现异常的情况下，什么时候立即放入呢，我们看下这个方法executePullRequestImmediately 的调用链：
调用地方有两个地方调用
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DefaultMQPushConsumerImpl.class中的pullMessage方法 -
“RebalancePushImpl.class 中的 dispatchPullRequest方法,这个是消息队列的负载均衡
客户端消息的拉取
所以很明显DefaultMQPushConsumerImpl.class中的pullMessage` 方法就是消息拉取的核心方法，我们来看看这个方法
public void pullMessage(final PullRequest pullRequest) {
// 1.获取处理队列ProcessQueue
final ProcessQueue processQueue = pullRequest.getProcessQueue();
// 2.如果dropped=true，那么return
if (processQueue.isDropped()) {
log.info("the pull request[{}] is dropped.", pullRequest.toString());
return;
}
//3.然后更新该消息队列最后一次拉取的时间
pullRequest.getProcessQueue().setLastPullTimestamp(System.currentTimeMillis());
try {
//4.如果消费者 服务状态不为ServiceState.RUNNING，默认延迟3秒再执行
this.makeSureStateOK();
} catch (MQClientException e) {
log.warn("pullMessage exception, consumer state not ok", e);
//4.1 延迟执行放入pullRequest操作
this.executePullRequestLater(pullRequest, pullTimeDelayMillsWhenException);
return;
}
//5.是否暂停，如果有那么延迟3s执行，目前我没有发现哪里有调用暂停，可能是为以后预留
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;
}
//6.消息的拉取会有流量控制，当processQueue没有消费的消息的数量达到（默认1000个）会触发流量控制
long cachedMessageCount = processQueue.getMsgCount().get();
long cachedMessageSizeInMiB = processQueue.getMsgSize().get() / (1024 * 1024);
if (cachedMessageCount > this.defaultMQPushConsumer.getPullThresholdForQueue()) {
//PullRequest延迟50ms后，放入LinkedBlockQueue中，每触发1000次打印一次警告
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;
}
//7.当processQueue中没有消费的消息体总大小 大于(默认100m)时，触发流控，
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;
}
//8.如果不是顺序消息，判断processQueue中消息的最大间距，就是消息的最大位置和最小位置的差值如果大于默认值2000，那么触发流控
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, pullTimeDelayMillsWhenException);
log.info("pull message later because not locked in broker, {}", pullRequest);
return;
}
}
//9.获取主题订阅信息
final SubscriptionData subscriptionData = this.rebalanceImpl.getSubscriptionInner().get(pullRequest.getMessageQueue().getTopic());
if (null == subscriptionData) {
this.executePullRequestLater(pullRequest, pullTimeDelayMillsWhenException);
log.warn("find the consumer's subscription failed, {}", pullRequest);
return;
}
final long beginTimestamp = System.currentTimeMillis();
//10.new一个回调方法，这个回调方法在broker端拉取完消息将调用
PullCallback pullCallback = new PullCallback() {
@Override
public void onSuccess(PullResult pullResult) {
if (pullResult != null) {
pullResult = DefaultMQPushConsumerImpl.this.pullAPIWrapper.processPullResult(pullRequest.getMessageQueue(), pullResult,
subscriptionData);
switch (pullResult.getPullStatus()) {
case FOUND:
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;
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());
boolean dispatchToConsume = processQueue.putMessage(pullResult.getMsgFoundList());
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:
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;
}
}
}
这里的源码比较长，我们重点看看消息拉取的核心方法
// 进入 this.pullAPIWrapper.pullKernelImpl 方法中
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 {
//15.查找Broker信息
FindBrokerResult findBrokerResult =
this.mQClientFactory.findBrokerAddressInSubscribe(mq.getBrokerName(),
this.recalculatePullFromWhichNode(mq), false);
//16.如果没有找到对应的broker，那么重新从nameServer拉取信息
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;
// 是否是从broker
if (findBrokerResult.isSlave()) {
sysFlagInner = PullSysFlag.clearCommitOffsetFlag(sysFlagInner);
}
// 构建消息请求头
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);
// 获取broker地址
String brokerAddr = findBrokerResult.getBrokerAddr();
if (PullSysFlag.hasClassFilterFlag(sysFlagInner)) {
brokerAddr = computePullFromWhichFilterServer(mq.getTopic(), brokerAddr);
}
/**
* 真正的消息拉取实现类 重要方法
*/
PullResult pullResult = this.mQClientFactory.getMQClientAPIImpl().pullMessage(
brokerAddr,
requestHeader,
timeoutMillis,
communicationMode,
pullCallback);
return pullResult;
}
throw new MQClientException("The broker[" + mq.getBrokerName() + "] not exist", null);
}
前面的一些是构建一些请求头，我们不看，重点看看this.mQClientFactory.getMQClientAPIImpl().pullMessage 方法，才是真正的消息拉取
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;
// 异步拉取消息
case ASYNC:
this.pullMessageAsync(addr, request, timeoutMillis, pullCallback);
return null;
// 同步拉取消息
case SYNC:
return this.pullMessageSync(addr, request, timeoutMillis);
default:
assert false;
break;
}
return null;
}
这里我们看看异步消息拉取的实现
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 {
PullResult pullResult = MQClientAPIImpl.this.processPullResponse(response, addr);
assert pullResult != null;
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()));
}
}
}
});
}
可以看到 就是基于Netty来拉取消息的。源码有点多，刚不动了，后续有时间继续分析消费者消费消息的源码，到这里消费者拉取消息的源码就分析的差不多了
带注释的源码地址
持续更新 https://github.com/weihubeats/rocketmq
原文始发于微信公众号（小奏技术）：干了几天的万字 RocketMQ Consumer启动流程及消息的拉取源码分析(保姆级分析)
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