聊聊storm TridentBoltExecutor的finishBatch方法

序

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 active
        TransactionStatus 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 transaction
                        Integer 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);
                }
            }
        }
    }

• MasterBatchCoordinator是整個trident的真正的spout，它的nextTuple方法會向TridentSpoutCoordinator向MasterBatchCoordinator.BATCH_STREAM_ID($batch)發射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));
        }
                
    }

• TridentSpoutCoordinator接收MasterBatchCoordinator在MasterBatchCoordinator.BATCH_STREAM_ID($batch)發過來的tuple，然後向包裝用戶spout的TridentBoltExecutor發送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 there
        
        
        TrackedBatch 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 tasks
        if(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 seen
                return;
            }
        }
        
        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;
    }

• TridentBoltExecutor.execute方法，首先會創建並初始化TrackedBatch(如果TrackedBatch不存在的話)，之後接收到batch指令的時候，對tracked.receivedTuple累加，然後調用_bolt.execute(tracked.info, tuple)
• 對於spout來說，這裏的_bolt是TridentSpoutExecutor，它的execute方法會往下游的TridentBoltExecutor發射一個batch的tuples；由於spout的expectedTaskReports==0，所以這裏在調用完TridentSpoutExecutor發射batch的tuples時，它就立馬調用finishBatch
• finishBatch操作，這裏會通過COORD_STREAM往下游的TridentBoltExecutor發射[id,count]數據，告知下游TridentBoltExecutor說它一共發射了多少tuples

TridentBoltExecutor(SubtopologyBolt)

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

    @Override
    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 there
        
        
        TrackedBatch 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 tasks
        if(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 seen
                return;
            }
        }
        
        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 received
                failBatch(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;
    }

• TridentBoltExecutor(SubtopologyBolt)是spout下游的bolt，它的_bolt是SubtopologyBolt，而且它的tracked.condition.expectedTaskReports不爲0，因而它是在接收到TupleType.COORD的tuple的時候，才進行checkFinish操作(這裏先忽略TupleType.COMMIT類型)
• 由於BoltExecutor是使用Utils.asyncLoop來挨個消費receiveQueue的數據的，而且emitBatch的時候也是挨個接收batch的tuples，最後再接收到TridentBoltExecutor(TridentSpoutExecutor)在finishBatch的時候通過COORD_STREAM發過來的[id,count]的tuple(注意這裏的COORD_STREAM是分發給每個task的，如果TridentBoltExecutor有多個parallel，則他們是按各自的task來接收的)
• 所以TridentBoltExecutor(SubtopologyBolt)先挨個處理每個tuple，處理完之後才輪到TupleType.COORD這個tuple，然後觸發checkFinish操作；在沒有commitStream的情況下，tracked.receivedCommit默認爲true，因而這裏只要檢測收到的tuples與應收的tuples數一致，就執行_bolt.finishBatch操作完成一個batch，然後再往它的下游TridentBoltExecutor發射它應收的[id,count]的tuple

小結

• 對於trident來說，真正的spout是MasterBatchCoordinator，它的nextTuple會觸發batch的發送，它將batch指令發送給TridentSpoutCoordinator，而TridentSpoutCoordinator將觸發TridentBoltExecutor(TridentSpoutExecutor)的execute方法，進而觸發ITridentSpout的emitter的emitBatch，從而發送一個batch的數據
• TridentBoltExecutor(TridentSpoutExecutor)的expectedTaskReports==0，它在調用完TridentSpoutExecutor發射batch的tuples時，就立馬調用finishBatch操作，通過COORD_STREAM往下游的TridentBoltExecutor發射[id,count]數據，告知下游TridentBoltExecutor說它一共發射了多少tuples
• spout的下游bolt爲TridentBoltExecutor(SubtopologyBolt)，它的tracked.condition.expectedTaskReports不爲0，因而它是在接收到TupleType.COORD的tuple的時候，才進行checkFinish操作(這裏先忽略TupleType.COMMIT類型)，由於spout是先執行emitBatch操作再最後finishBatch發送[id,count]數據，正常情況下按順序進入到TridentBoltExecutor(SubtopologyBolt)的receiveQueue隊列，然後TridentBoltExecutor(SubtopologyBolt)挨個消費tuple，調用SubtopologyBolt.execute，最後再處理[id,count]數據，觸發checkFinish操作，只要檢測收到的tuples與應收的tuples數一致，就執行SubtopologyBolt.finishBatch操作完成這個batch，然後再往它的下游TridentBoltExecutor發射它應收的[id,count]的tuple

doc

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