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本文主要研究一下storm TridentBoltExecutor的finishBatch方法

MasterBatchCoordinator.nextTuple

storm-core-1.2.2-sources.jar!/org/apache/storm/trident/topology/MasterBatchCoordinator.java

    public void nextTuple() {sync();}private void sync() {// note that sometimes the tuples active may be less than max_spout_pending, e.g.// max_spout_pending = 3// tx 1, 2, 3 active, tx 2 is acked. there won't be a commit for tx 2 (because tx 1 isn't committed yet),// and there won't be a batch for tx 4 because there's max_spout_pending tx activeTransactionStatus maybeCommit = _activeTx.get(_currTransaction);if(maybeCommit!=null && maybeCommit.status == AttemptStatus.PROCESSED) {maybeCommit.status = AttemptStatus.COMMITTING;_collector.emit(COMMIT_STREAM_ID, new Values(maybeCommit.attempt), maybeCommit.attempt);LOG.debug("Emitted on [stream = {}], [tx_status = {}], [{}]", COMMIT_STREAM_ID, maybeCommit, this);}if(_active) {if(_activeTx.size() < _maxTransactionActive) {Long curr = _currTransaction;for(int i=0; i<_maxTransactionActive; i++) {if(!_activeTx.containsKey(curr) && isReady(curr)) {// by using a monotonically increasing attempt id, downstream tasks// can be memory efficient by clearing out state for old attempts// as soon as they see a higher attempt id for a transactionInteger attemptId = _attemptIds.get(curr);if(attemptId==null) {attemptId = 0;} else {attemptId++;}_attemptIds.put(curr, attemptId);for(TransactionalState state: _states) {state.setData(CURRENT_ATTEMPTS, _attemptIds);}TransactionAttempt attempt = new TransactionAttempt(curr, attemptId);final TransactionStatus newTransactionStatus = new TransactionStatus(attempt);_activeTx.put(curr, newTransactionStatus);_collector.emit(BATCH_STREAM_ID, new Values(attempt), attempt);LOG.debug("Emitted on [stream = {}], [tx_attempt = {}], [tx_status = {}], [{}]", BATCH_STREAM_ID, attempt, newTransactionStatus, this);_throttler.markEvent();}curr = nextTransactionId(curr);}}}}
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• MasterBatchCoordinator是整个trident的真正的spout，它的nextTuple方法会向TridentSpoutCoordinator向MasterBatchCoordinator.BATCH_STREAM_ID($batch)发射tuple

TridentSpoutCoordinator.execute

storm-core-1.2.2-sources.jar!/org/apache/storm/trident/spout/TridentSpoutCoordinator.java

    public void execute(Tuple tuple, BasicOutputCollector collector) {TransactionAttempt attempt = (TransactionAttempt) tuple.getValue(0);if(tuple.getSourceStreamId().equals(MasterBatchCoordinator.SUCCESS_STREAM_ID)) {_state.cleanupBefore(attempt.getTransactionId());_coord.success(attempt.getTransactionId());} else {long txid = attempt.getTransactionId();Object prevMeta = _state.getPreviousState(txid);Object meta = _coord.initializeTransaction(txid, prevMeta, _state.getState(txid));_state.overrideState(txid, meta);collector.emit(MasterBatchCoordinator.BATCH_STREAM_ID, new Values(attempt, meta));}}
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• TridentSpoutCoordinator接收MasterBatchCoordinator在MasterBatchCoordinator.BATCH_STREAM_ID($batch)发过来的tuple，然后向包装用户spout的TridentBoltExecutor发送batch指令

TridentBoltExecutor(TridentSpoutExecutor)

storm-core-1.2.2-sources.jar!/org/apache/storm/trident/topology/TridentBoltExecutor.java

    public void execute(Tuple tuple) {if(TupleUtils.isTick(tuple)) {long now = System.currentTimeMillis();if(now - _lastRotate > _messageTimeoutMs) {_batches.rotate();_lastRotate = now;}return;}String batchGroup = _batchGroupIds.get(tuple.getSourceGlobalStreamId());if(batchGroup==null) {// this is so we can do things like have simple DRPC that doesn't need to use batch processing_coordCollector.setCurrBatch(null);_bolt.execute(null, tuple);_collector.ack(tuple);return;}IBatchID id = (IBatchID) tuple.getValue(0);//get transaction id//if it already exists and attempt id is greater than the attempt thereTrackedBatch tracked = (TrackedBatch) _batches.get(id.getId());
//        if(_batches.size() > 10 && _context.getThisTaskIndex() == 0) {
//            System.out.println("Received in " + _context.getThisComponentId() + " " + _context.getThisTaskIndex()
//                    + " (" + _batches.size() + ")" +
//                    "\ntuple: " + tuple +
//                    "\nwith tracked " + tracked +
//                    "\nwith id " + id +
//                    "\nwith group " + batchGroup
//                    + "\n");
//
//        }//System.out.println("Num tracked: " + _batches.size() + " " + _context.getThisComponentId() + " " + _context.getThisTaskIndex());// this code here ensures that only one attempt is ever tracked for a batch, so when// failures happen you don't get an explosion in memory usage in the tasksif(tracked!=null) {if(id.getAttemptId() > tracked.attemptId) {_batches.remove(id.getId());tracked = null;} else if(id.getAttemptId() < tracked.attemptId) {// no reason to try to execute a previous attempt than we've already seenreturn;}}if(tracked==null) {tracked = new TrackedBatch(new BatchInfo(batchGroup, id, _bolt.initBatchState(batchGroup, id)), _coordConditions.get(batchGroup), id.getAttemptId());_batches.put(id.getId(), tracked);}_coordCollector.setCurrBatch(tracked);//System.out.println("TRACKED: " + tracked + " " + tuple);TupleType t = getTupleType(tuple, tracked);if(t==TupleType.COMMIT) {tracked.receivedCommit = true;checkFinish(tracked, tuple, t);} else if(t==TupleType.COORD) {int count = tuple.getInteger(1);tracked.reportedTasks++;tracked.expectedTupleCount+=count;checkFinish(tracked, tuple, t);} else {tracked.receivedTuples++;boolean success = true;try {_bolt.execute(tracked.info, tuple);if(tracked.condition.expectedTaskReports==0) {success = finishBatch(tracked, tuple);}} catch(FailedException e) {failBatch(tracked, e);}if(success) {_collector.ack(tuple);                   } else {_collector.fail(tuple);}}_coordCollector.setCurrBatch(null);}private boolean finishBatch(TrackedBatch tracked, Tuple finishTuple) {boolean success = true;try {_bolt.finishBatch(tracked.info);String stream = COORD_STREAM(tracked.info.batchGroup);for(Integer task: tracked.condition.targetTasks) {_collector.emitDirect(task, stream, finishTuple, new Values(tracked.info.batchId, Utils.get(tracked.taskEmittedTuples, task, 0)));}if(tracked.delayedAck!=null) {_collector.ack(tracked.delayedAck);tracked.delayedAck = null;}} catch(FailedException e) {failBatch(tracked, e);success = false;}_batches.remove(tracked.info.batchId.getId());return success;}
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• TridentBoltExecutor.execute方法，首先会创建并初始化TrackedBatch(如果TrackedBatch不存在的话)，之后接收到batch指令的时候，对tracked.receivedTuple累加，然后调用_bolt.execute(tracked.info, tuple)
• 对于spout来说，这里的_bolt是TridentSpoutExecutor，它的execute方法会往下游的TridentBoltExecutor发射一个batch的tuples；由于spout的expectedTaskReports==0，所以这里在调用完TridentSpoutExecutor发射batch的tuples时，它就立马调用finishBatch
• finishBatch操作，这里会通过COORD_STREAM往下游的TridentBoltExecutor发射[id,count]数据，告知下游TridentBoltExecutor说它一共发射了多少tuples

TridentBoltExecutor(SubtopologyBolt)

storm-core-1.2.2-sources.jar!/org/apache/storm/trident/topology/TridentBoltExecutor.java

    @Overridepublic void execute(Tuple tuple) {if(TupleUtils.isTick(tuple)) {long now = System.currentTimeMillis();if(now - _lastRotate > _messageTimeoutMs) {_batches.rotate();_lastRotate = now;}return;}String batchGroup = _batchGroupIds.get(tuple.getSourceGlobalStreamId());if(batchGroup==null) {// this is so we can do things like have simple DRPC that doesn't need to use batch processing_coordCollector.setCurrBatch(null);_bolt.execute(null, tuple);_collector.ack(tuple);return;}IBatchID id = (IBatchID) tuple.getValue(0);//get transaction id//if it already exists and attempt id is greater than the attempt thereTrackedBatch tracked = (TrackedBatch) _batches.get(id.getId());
//        if(_batches.size() > 10 && _context.getThisTaskIndex() == 0) {
//            System.out.println("Received in " + _context.getThisComponentId() + " " + _context.getThisTaskIndex()
//                    + " (" + _batches.size() + ")" +
//                    "\ntuple: " + tuple +
//                    "\nwith tracked " + tracked +
//                    "\nwith id " + id +
//                    "\nwith group " + batchGroup
//                    + "\n");
//
//        }//System.out.println("Num tracked: " + _batches.size() + " " + _context.getThisComponentId() + " " + _context.getThisTaskIndex());// this code here ensures that only one attempt is ever tracked for a batch, so when// failures happen you don't get an explosion in memory usage in the tasksif(tracked!=null) {if(id.getAttemptId() > tracked.attemptId) {_batches.remove(id.getId());tracked = null;} else if(id.getAttemptId() < tracked.attemptId) {// no reason to try to execute a previous attempt than we've already seenreturn;}}if(tracked==null) {tracked = new TrackedBatch(new BatchInfo(batchGroup, id, _bolt.initBatchState(batchGroup, id)), _coordConditions.get(batchGroup), id.getAttemptId());_batches.put(id.getId(), tracked);}_coordCollector.setCurrBatch(tracked);//System.out.println("TRACKED: " + tracked + " " + tuple);TupleType t = getTupleType(tuple, tracked);if(t==TupleType.COMMIT) {tracked.receivedCommit = true;checkFinish(tracked, tuple, t);} else if(t==TupleType.COORD) {int count = tuple.getInteger(1);tracked.reportedTasks++;tracked.expectedTupleCount+=count;checkFinish(tracked, tuple, t);} else {tracked.receivedTuples++;boolean success = true;try {_bolt.execute(tracked.info, tuple);if(tracked.condition.expectedTaskReports==0) {success = finishBatch(tracked, tuple);}} catch(FailedException e) {failBatch(tracked, e);}if(success) {_collector.ack(tuple);                   } else {_collector.fail(tuple);}}_coordCollector.setCurrBatch(null);}private void checkFinish(TrackedBatch tracked, Tuple tuple, TupleType type) {if(tracked.failed) {failBatch(tracked);_collector.fail(tuple);return;}CoordCondition cond = tracked.condition;boolean delayed = tracked.delayedAck==null &&(cond.commitStream!=null && type==TupleType.COMMIT|| cond.commitStream==null);if(delayed) {tracked.delayedAck = tuple;}boolean failed = false;if(tracked.receivedCommit && tracked.reportedTasks == cond.expectedTaskReports) {if(tracked.receivedTuples == tracked.expectedTupleCount) {finishBatch(tracked, tuple);                } else {//TODO: add logging that not all tuples were receivedfailBatch(tracked);_collector.fail(tuple);failed = true;}}if(!delayed && !failed) {_collector.ack(tuple);}}private boolean finishBatch(TrackedBatch tracked, Tuple finishTuple) {boolean success = true;try {_bolt.finishBatch(tracked.info);String stream = COORD_STREAM(tracked.info.batchGroup);for(Integer task: tracked.condition.targetTasks) {_collector.emitDirect(task, stream, finishTuple, new Values(tracked.info.batchId, Utils.get(tracked.taskEmittedTuples, task, 0)));}if(tracked.delayedAck!=null) {_collector.ack(tracked.delayedAck);tracked.delayedAck = null;}} catch(FailedException e) {failBatch(tracked, e);success = false;}_batches.remove(tracked.info.batchId.getId());return success;}
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• TridentBoltExecutor(SubtopologyBolt)是spout下游的bolt，它的_bolt是SubtopologyBolt，而且它的tracked.condition.expectedTaskReports不为0，因而它是在接收到TupleType.COORD的tuple的时候，才进行checkFinish操作(这里先忽略TupleType.COMMIT类型)
• 由于BoltExecutor是使用Utils.asyncLoop来挨个消费receiveQueue的数据的，而且emitBatch的时候也是挨个接收batch的tuples，最后再接收到TridentBoltExecutor(TridentSpoutExecutor)在finishBatch的时候通过COORD_STREAM发过来的[id,count]的tuple(注意这里的COORD_STREAM是分发给每个task的，如果TridentBoltExecutor有多个parallel，则他们是按各自的task来接收的)
• 所以TridentBoltExecutor(SubtopologyBolt)先挨个处理每个tuple，处理完之后才轮到TupleType.COORD这个tuple，然后触发checkFinish操作；在没有commitStream的情况下，tracked.receivedCommit默认为true，因而这里只要检测收到的tuples与应收的tuples数一致，就执行_bolt.finishBatch操作完成一个batch，然后再往它的下游TridentBoltExecutor发射它应收的[id,count]的tuple

小结

• 对于trident来说，真正的spout是MasterBatchCoordinator，它的nextTuple会触发batch的发送，它将batch指令发送给TridentSpoutCoordinator，而TridentSpoutCoordinator将触发TridentBoltExecutor(TridentSpoutExecutor)的execute方法，进而触发ITridentSpout的emitter的emitBatch，从而发送一个batch的数据
• TridentBoltExecutor(TridentSpoutExecutor)的expectedTaskReports==0，它在调用完TridentSpoutExecutor发射batch的tuples时，就立马调用finishBatch操作，通过COORD_STREAM往下游的TridentBoltExecutor发射[id,count]数据，告知下游TridentBoltExecutor说它一共发射了多少tuples
• spout的下游bolt为TridentBoltExecutor(SubtopologyBolt)，它的tracked.condition.expectedTaskReports不为0，因而它是在接收到TupleType.COORD的tuple的时候，才进行checkFinish操作(这里先忽略TupleType.COMMIT类型)，由于spout是先执行emitBatch操作再最后finishBatch发送[id,count]数据，正常情况下按顺序进入到TridentBoltExecutor(SubtopologyBolt)的receiveQueue队列，然后TridentBoltExecutor(SubtopologyBolt)挨个消费tuple，调用SubtopologyBolt.execute，最后再处理[id,count]数据，触发checkFinish操作，只要检测收到的tuples与应收的tuples数一致，就执行SubtopologyBolt.finishBatch操作完成这个batch，然后再往它的下游TridentBoltExecutor发射它应收的[id,count]的tuple

doc

• Trident Tutorial
• 聊聊storm worker的executor与task
• 聊聊storm的AggregateProcessor的execute及finishBatch方法