RocketMQ 源码分析 —— Filtersrv

1. 概述

Filtersrv ，负责自定义规则过滤 Consumer 从 Broker 拉取的消息。

为什么 Broker 不提供过滤消息的功能呢？我们来看看官方的说法：

• Broker 端消息过滤
  在 Broker 中，按照 Consumer 的要求做过滤，优点是减少了对于 Consumer 无用消息的网络传输。 缺点是增加了 Broker 的负担，实现相对复杂。
  (1). 淘宝 Notify 支持多种过滤方式，包含直接按照消息类型过滤，灵活的语法表达式过滤，几乎可以满足最苛刻的过滤需求。
  (2). 淘宝 RocketMQ 支持按照简单的 Message Tag 过滤，也支持按照 Message Header、body 进行过滤。
  (3). CORBA Notification 规范中也支持灵活的语法表达式过滤。
• Consumer 端消息过滤
  这种过滤方式可由应用完全自定义实现，但是缺点是很多无用的消息要传输到 Consumer 端。

就是在这种考虑下，Filtersrv 出现了。减少了 Broker 的负担，又减少了 Consumer 接收无用的消息。当然缺点也是有的，多了一层 Filtersrv 网络开销。

2. Filtersrv 注册到 Broker

• ???? 一个 Filtersrv 只对应一个 Broker。
• ???? 一个 Broker 可以对应多个 Filtersrv。Filtersrv 的高可用通过启动多个 Filtersrv 实现。
• ???? Filtersrv 注册失败时，主动退出关闭。

核心代码如下：

1: // ⬇️⬇️⬇️【FiltersrvController.java】
 2: public boolean initialize() {
 3:     // ....(省略代码)
 4: 
 5:     // 固定间隔注册到Broker
 6:     this.scheduledExecutorService.scheduleAtFixedRate(new Runnable() {
 7: 
 8:         @Override
 9:         public void run() {
10:             FiltersrvController.this.registerFilterServerToBroker();
11:         }
12:     }, 15, 10, TimeUnit.SECONDS); // TODO edit by 芋艿：initialDelay时间太短，可能导致初始化失败。从3=》15
13: 
14:     // ....(省略代码)
15: }
16: 
17: /**
18:  * 注册Filtersrv 到 Broker
19:  * ！！！如果注册失败，关闭Filtersrv
20:  */
21: public void registerFilterServerToBroker() {
22:     try {
23:         RegisterFilterServerResponseHeader responseHeader =
24:             this.filterServerOuterAPI.registerFilterServerToBroker(
25:                 this.filtersrvConfig.getConnectWhichBroker(), this.localAddr());
26:         this.defaultMQPullConsumer.getDefaultMQPullConsumerImpl().getPullAPIWrapper()
27:             .setDefaultBrokerId(responseHeader.getBrokerId());
28: 
29:         if (null == this.brokerName) {
30:             this.brokerName = responseHeader.getBrokerName();
31:         }
32: 
33:         log.info("register filter server<{}> to broker<{}> OK, Return: {} {}",
34:             this.localAddr(),
35:             this.filtersrvConfig.getConnectWhichBroker(),
36:             responseHeader.getBrokerName(),
37:             responseHeader.getBrokerId());
38:     } catch (Exception e) {
39:         log.warn("register filter server Exception", e);
40: 
41:         log.warn("access broker failed, kill oneself");
42:         System.exit(-1); // 异常退出
43:     }
44: }

3. 过滤类

3.1 Consumer 订阅时设置 过滤类代码

• ???? Consumer 针对每个 Topic 可以订阅不同的 过滤类代码。

1: // ⬇️⬇️⬇️【DefaultMQPushConsumer.java】
2: @Override
3: public void subscribe(String topic, String fullClassName, String filterClassSource) throws MQClientException {
4:     this.defaultMQPushConsumerImpl.subscribe(topic, fullClassName, filterClassSource);
5: }

3.2 Consumer 上传 过滤类代码

• ???? Consumer 心跳注册到 Broker 的同时，上传 过滤类代码 到 Broker 对应的所有 Filtersrv。

1: // ⬇️⬇️⬇️【MQClientInstance.java】
 2: /**
 3:  * 发送心跳到Broker，上传过滤类源码到Filtersrv
 4:  */
 5: public void sendHeartbeatToAllBrokerWithLock() {
 6:     if (this.lockHeartbeat.tryLock()) {
 7:         try {
 8:             this.sendHeartbeatToAllBroker();
 9:             this.uploadFilterClassSource();
10:         } catch (final Exception e) {
11:             log.error("sendHeartbeatToAllBroker exception", e);
12:         } finally {
13:             this.lockHeartbeat.unlock();
14:         }
15:     } else {
16:         log.warn("lock heartBeat, but failed.");
17:     }
18: }
19: 
20: /**
21:  * 上传过滤类到Filtersrv
22:  */
23: private void uploadFilterClassSource() {
24:     Iterator<Entry<String, MQConsumerInner>> it = this.consumerTable.entrySet().iterator();
25:     while (it.hasNext()) {
26:         Entry<String, MQConsumerInner> next = it.next();
27:         MQConsumerInner consumer = next.getValue();
28:         if (ConsumeType.CONSUME_PASSIVELY == consumer.consumeType()) {
29:             Set<SubscriptionData> subscriptions = consumer.subscriptions();
30:             for (SubscriptionData sub : subscriptions) {
31:                 if (sub.isClassFilterMode() && sub.getFilterClassSource() != null) {
32:                     final String consumerGroup = consumer.groupName();
33:                     final String className = sub.getSubString();
34:                     final String topic = sub.getTopic();
35:                     final String filterClassSource = sub.getFilterClassSource();
36:                     try {
37:                         this.uploadFilterClassToAllFilterServer(consumerGroup, className, topic, filterClassSource);
38:                     } catch (Exception e) {
39:                         log.error("uploadFilterClassToAllFilterServer Exception", e);
40:                     }
41:                 }
42:             }
43:         }
44:     }
45: }

3.3 Filter 编译 过滤类代码

• ???? Filtersrv 处理 Consumer 上传的 过滤类代码，并进行编译使用。

核心代码如下：

 1: // ⬇️⬇️⬇️【FilterClassManager.java】
 2: /**
 3:  * 注册过滤类
 4:  *
 5:  * @param consumerGroup 消费分组
 6:  * @param topic Topic
 7:  * @param className 过滤类名
 8:  * @param classCRC 过滤类源码CRC
 9:  * @param filterSourceBinary 过滤类源码
10:  * @return 是否注册成功
11:  */
12: public boolean registerFilterClass(final String consumerGroup, final String topic,
13:     final String className, final int classCRC, final byte[] filterSourceBinary) {
14:     final String key = buildKey(consumerGroup, topic);
15:     // 判断是否要注册新的过滤类
16:     boolean registerNew = false;
17:     FilterClassInfo filterClassInfoPrev = this.filterClassTable.get(key);
18:     if (null == filterClassInfoPrev) {
19:         registerNew = true;
20:     } else {
21:         if (this.filtersrvController.getFiltersrvConfig().isClientUploadFilterClassEnable()) {
22:             if (filterClassInfoPrev.getClassCRC() != classCRC && classCRC != 0) { // 类有变化
23:                 registerNew = true;
24:             }
25:         }
26:     }
27:     // 注册新的过滤类
28:     if (registerNew) {
29:         synchronized (this.compileLock) {
30:             filterClassInfoPrev = this.filterClassTable.get(key);
31:             if (null != filterClassInfoPrev && filterClassInfoPrev.getClassCRC() == classCRC) {
32:                 return true;
33:             }
34:             try {
35:                 FilterClassInfo filterClassInfoNew = new FilterClassInfo();
36:                 filterClassInfoNew.setClassName(className);
37:                 filterClassInfoNew.setClassCRC(0);
38:                 filterClassInfoNew.setMessageFilter(null);
39: 
40:                 if (this.filtersrvController.getFiltersrvConfig().isClientUploadFilterClassEnable()) {
41:                     String javaSource = new String(filterSourceBinary, MixAll.DEFAULT_CHARSET);
42:                     // 编译新的过滤类
43:                     Class<?> newClass = DynaCode.compileAndLoadClass(className, javaSource);
44:                     // 创建新的过滤类对象
45:                     Object newInstance = newClass.newInstance();
46:                     filterClassInfoNew.setMessageFilter((MessageFilter) newInstance);
47:                     filterClassInfoNew.setClassCRC(classCRC);
48:                 }
49: 
50:                 this.filterClassTable.put(key, filterClassInfoNew);
51:             } catch (Throwable e) {
52:                 String info = String.format("FilterServer, registerFilterClass Exception, consumerGroup: %s topic: %s className: %s",
53:                             consumerGroup, topic, className);
54:                 log.error(info, e);
55:                 return false;
56:             }
57:         }
58:     }
59: 
60:     return true;
61: }

4. 过滤消息

4.1 Consumer 从 Filtersrv 拉取消息

• ???? Consumer 拉取 使用过滤类方式订阅 的消费消息时，从 Broker 对应的 Filtersrv 列表随机选择一个拉取消息。如果选择不到 Filtersrv，则无法拉取消息。因此，Filtersrv 一定要做高可用。

1: // ⬇️⬇️⬇️【PullAPIWrapper.java】
 2: /**
 3:  * 拉取消息核心方法
 4:  *
 5:  * @param mq 消息嘟列
 6:  * @param subExpression 订阅表达式
 7:  * @param subVersion 订阅版本号
 8:  * @param offset 拉取队列开始位置
 9:  * @param maxNums 批量拉 取消息数量
10:  * @param sysFlag 拉取系统标识
11:  * @param commitOffset 提交消费进度
12:  * @param brokerSuspendMaxTimeMillis broker挂起请求最大时间
13:  * @param timeoutMillis 请求broker超时时间
14:  * @param communicationMode 通讯模式
15:  * @param pullCallback 拉取回调
16:  * @return 拉取消息结果。只有通讯模式为同步时，才返回结果，否则返回null。
17:  * @throws MQClientException 当寻找不到 broker 时，或发生其他client异常
18:  * @throws RemotingException 当远程调用发生异常时
19:  * @throws MQBrokerException 当 broker 发生异常时。只有通讯模式为同步时才会发生该异常。
20:  * @throws InterruptedException 当发生中断异常时
21:  */
22: protected PullResult pullKernelImpl(
23:     final MessageQueue mq,
24:     final String subExpression,
25:     final long subVersion,
26:     final long offset,
27:     final int maxNums,
28:     final int sysFlag,
29:     final long commitOffset,
30:     final long brokerSuspendMaxTimeMillis,
31:     final long timeoutMillis,
32:     final CommunicationMode communicationMode,
33:     final PullCallback pullCallback
34: ) throws MQClientException, RemotingException, MQBrokerException, InterruptedException {
35:     // // ....(省略代码)
36:     // 请求拉取消息
37:     if (findBrokerResult != null) {
38:         // ....(省略代码)
39:         // 若订阅topic使用过滤类，使用filtersrv获取消息
40:         String brokerAddr = findBrokerResult.getBrokerAddr();
41:         if (PullSysFlag.hasClassFilterFlag(sysFlagInner)) {
42:             brokerAddr = computPullFromWhichFilterServer(mq.getTopic(), brokerAddr);
43:         }
44: 
45:         PullResult pullResult = this.mQClientFactory.getMQClientAPIImpl().pullMessage(
46:             brokerAddr,
47:             requestHeader,
48:             timeoutMillis,
49:             communicationMode,
50:             pullCallback);
51: 
52:         return pullResult;
53:     }
54: 
55:     // Broker信息不存在，则抛出异常
56:     throw new MQClientException("The broker[" + mq.getBrokerName() + "] not exist", null);
57: }
58: 
59: /**
60:  * 计算filtersrv地址。如果有多个filtersrv，随机选择一个。
61:  *
62:  * @param topic Topic
63:  * @param brokerAddr broker地址
64:  * @return filtersrv地址
65:  * @throws MQClientException 当filtersrv不存在时
66:  */
67: private String computPullFromWhichFilterServer(final String topic, final String brokerAddr)
68:     throws MQClientException {
69:     ConcurrentHashMap<String, TopicRouteData> topicRouteTable = this.mQClientFactory.getTopicRouteTable();
70:     if (topicRouteTable != null) {
71:         TopicRouteData topicRouteData = topicRouteTable.get(topic);
72:         List<String> list = topicRouteData.getFilterServerTable().get(brokerAddr);
73:         if (list != null && !list.isEmpty()) {
74:             return list.get(randomNum() % list.size());
75:         }
76:     }
77:     throw new MQClientException("Find Filter Server Failed, Broker Addr: " + brokerAddr + " topic: "
78:         + topic, null);
79: }

4.2 Filtersrv 从 Broker 拉取消息

• ???? Filtersrv 拉取消息后，会建议 Consumer 向 Broker主节点 拉取消息。
• ???? Filtersrv 可以理解成一个 Consumer，向 Broker 拉取消息时，实际使用的 DefaultMQPullConsumer.java 的方法和逻辑。

 1: // ⬇️⬇️⬇️【DefaultRequestProcessor.java】
  2: /**
  3:  * 拉取消息
  4:  *
  5:  * @param ctx 拉取消息context
  6:  * @param request 拉取消息请求
  7:  * @return 响应
  8:  * @throws Exception 当发生异常时
  9:  */
 10: private RemotingCommand pullMessageForward(final ChannelHandlerContext ctx, final RemotingCommand request) throws Exception {
 11:     final RemotingCommand response = RemotingCommand.createResponseCommand(PullMessageResponseHeader.class);
 12:     final PullMessageResponseHeader responseHeader = (PullMessageResponseHeader) response.readCustomHeader();
 13:     final PullMessageRequestHeader requestHeader =
 14:         (PullMessageRequestHeader) request.decodeCommandCustomHeader(PullMessageRequestHeader.class);
 15: 
 16:     final FilterContext filterContext = new FilterContext();
 17:     filterContext.setConsumerGroup(requestHeader.getConsumerGroup());
 18: 
 19:     response.setOpaque(request.getOpaque());
 20: 
 21:     DefaultMQPullConsumer pullConsumer = this.filtersrvController.getDefaultMQPullConsumer();
 22: 
 23:     // 校验Topic过滤类是否完整
 24:     final FilterClassInfo findFilterClass = this.filtersrvController.getFilterClassManager().findFilterClass(requestHeader.getConsumerGroup(), requestHeader.getTopic());
 25:     if (null == findFilterClass) {
 26:         response.setCode(ResponseCode.SYSTEM_ERROR);
 27:         response.setRemark("Find Filter class failed, not registered");
 28:         return response;
 29:     }
 30:     if (null == findFilterClass.getMessageFilter()) {
 31:         response.setCode(ResponseCode.SYSTEM_ERROR);
 32:         response.setRemark("Find Filter class failed, registered but no class");
 33:         return response;
 34:     }
 35: 
 36:     // 设置下次请求从 Broker主节点。
 37:     responseHeader.setSuggestWhichBrokerId(MixAll.MASTER_ID);
 38: 
 39:     MessageQueue mq = new MessageQueue();
 40:     mq.setTopic(requestHeader.getTopic());
 41:     mq.setQueueId(requestHeader.getQueueId());
 42:     mq.setBrokerName(this.filtersrvController.getBrokerName());
 43:     long offset = requestHeader.getQueueOffset();
 44:     int maxNums = requestHeader.getMaxMsgNums();
 45: 
 46:     final PullCallback pullCallback = new PullCallback() {
 47: 
 48:         @Override
 49:         public void onSuccess(PullResult pullResult) {
 50:             responseHeader.setMaxOffset(pullResult.getMaxOffset());
 51:             responseHeader.setMinOffset(pullResult.getMinOffset());
 52:             responseHeader.setNextBeginOffset(pullResult.getNextBeginOffset());
 53:             response.setRemark(null);
 54: 
 55:             switch (pullResult.getPullStatus()) {
 56:                 case FOUND:
 57:                     response.setCode(ResponseCode.SUCCESS);
 58: 
 59:                     List<MessageExt> msgListOK = new ArrayList<MessageExt>();
 60:                     try {
 61:                         for (MessageExt msg : pullResult.getMsgFoundList()) {
 62:                             // 使用过滤类过滤消息
 63:                             boolean match = findFilterClass.getMessageFilter().match(msg, filterContext);
 64:                             if (match) {
 65:                                 msgListOK.add(msg);
 66:                             }
 67:                         }
 68: 
 69:                         if (!msgListOK.isEmpty()) {
 70:                             returnResponse(requestHeader.getConsumerGroup(), requestHeader.getTopic(), ctx, response, msgListOK);
 71:                             return;
 72:                         } else {
 73:                             response.setCode(ResponseCode.PULL_RETRY_IMMEDIATELY);
 74:                         }
 75:                     } catch (Throwable e) {
 76:                         final String error =
 77:                             String.format("do Message Filter Exception, ConsumerGroup: %s Topic: %s ",
 78:                                 requestHeader.getConsumerGroup(), requestHeader.getTopic());
 79:                         log.error(error, e);
 80: 
 81:                         response.setCode(ResponseCode.SYSTEM_ERROR);
 82:                         response.setRemark(error + RemotingHelper.exceptionSimpleDesc(e));
 83:                         returnResponse(requestHeader.getConsumerGroup(), requestHeader.getTopic(), ctx, response, null);
 84:                         return;
 85:                     }
 86: 
 87:                     break;
 88:                 case NO_MATCHED_MSG:
 89:                     response.setCode(ResponseCode.PULL_RETRY_IMMEDIATELY);
 90:                     break;
 91:                 case NO_NEW_MSG:
 92:                     response.setCode(ResponseCode.PULL_NOT_FOUND);
 93:                     break;
 94:                 case OFFSET_ILLEGAL:
 95:                     response.setCode(ResponseCode.PULL_OFFSET_MOVED);
 96:                     break;
 97:                 default:
 98:                     break;
 99:             }
100: 
101:             returnResponse(requestHeader.getConsumerGroup(), requestHeader.getTopic(), ctx, response, null);
102:         }
103: 
104:         @Override
105:         public void onException(Throwable e) {
106:             response.setCode(ResponseCode.SYSTEM_ERROR);
107:             response.setRemark("Pull Callback Exception, " + RemotingHelper.exceptionSimpleDesc(e));
108:             returnResponse(requestHeader.getConsumerGroup(), requestHeader.getTopic(), ctx, response, null);
109:             return;
110:         }
111:     };
112: 
113:     // 拉取消息
114:     pullConsumer.pullBlockIfNotFound(mq, null, offset, maxNums, pullCallback);
115:     return null;
116: }

5. Filtersrv 高可用