序
本文主要研究一下storm的window trigger
WindowTridentProcessor.prepare
storm-core-1.2.2-sources.jar!/org/apache/storm/trident/windowing/WindowTridentProcessor.java
public void prepare(Map stormConf, TopologyContext context, TridentContext tridentContext) {
this.topologyContext = context;
List<TridentTuple.Factory> parents = tridentContext.getParentTupleFactories();
if (parents.size() != 1) {
throw new RuntimeException("Aggregation related operation can only have one parent");
}
Long maxTuplesCacheSize = getWindowTuplesCacheSize(stormConf);
this.tridentContext = tridentContext;
collector = new FreshCollector(tridentContext);
projection = new TridentTupleView.ProjectionFactory(parents.get(0), inputFields);
windowStore = windowStoreFactory.create(stormConf);
windowTaskId = windowId + WindowsStore.KEY_SEPARATOR + topologyContext.getThisTaskId() + WindowsStore.KEY_SEPARATOR;
windowTriggerInprocessId = getWindowTriggerInprocessIdPrefix(windowTaskId);
tridentWindowManager = storeTuplesInStore ?
new StoreBasedTridentWindowManager(windowConfig, windowTaskId, windowStore, aggregator, tridentContext.getDelegateCollector(), maxTuplesCacheSize, inputFields)
: new InMemoryTridentWindowManager(windowConfig, windowTaskId, windowStore, aggregator, tridentContext.getDelegateCollector());
tridentWindowManager.prepare();
}- 這裏調用了tridentWindowManager.prepare()
AbstractTridentWindowManager.prepare
storm-core-1.2.2-sources.jar!/org/apache/storm/trident/windowing/AbstractTridentWindowManager.java
public AbstractTridentWindowManager(WindowConfig windowConfig, String windowTaskId, WindowsStore windowStore,
Aggregator aggregator, BatchOutputCollector delegateCollector) {
this.windowTaskId = windowTaskId;
this.windowStore = windowStore;
this.aggregator = aggregator;
this.delegateCollector = delegateCollector;
windowTriggerCountId = WindowTridentProcessor.TRIGGER_COUNT_PREFIX + windowTaskId;
windowManager = new WindowManager<>(new TridentWindowLifeCycleListener());
WindowStrategy<T> windowStrategy = windowConfig.getWindowStrategy();
EvictionPolicy<T> evictionPolicy = windowStrategy.getEvictionPolicy();
windowManager.setEvictionPolicy(evictionPolicy);
triggerPolicy = windowStrategy.getTriggerPolicy(windowManager, evictionPolicy);
windowManager.setTriggerPolicy(triggerPolicy);
}
public void prepare() {
preInitialize();
initialize();
postInitialize();
}
private void postInitialize() {
// start trigger once the initialization is done.
triggerPolicy.start();
}- AbstractTridentWindowManager在構造器裏頭調用windowStrategy.getTriggerPolicy獲取triggerPolicy；prepare方法調用了postInitialize，而它觸發triggerPolicy.start()
SlidingDurationWindowStrategy.getTriggerPolicy
storm-core-1.2.2-sources.jar!/org/apache/storm/trident/windowing/strategy/SlidingDurationWindowStrategy.java
/**
* Returns a {@code TriggerPolicy} which triggers for every configured sliding window duration.
*
* @param triggerHandler
* @param evictionPolicy
* @return
*/
@Override
public TriggerPolicy<T> getTriggerPolicy(TriggerHandler triggerHandler, EvictionPolicy<T> evictionPolicy) {
return new TimeTriggerPolicy<>(windowConfig.getSlidingLength(), triggerHandler, evictionPolicy);
}- 以SlidingDurationWindowStrategy爲例，這裏創建的是TimeTriggerPolicy，其duration爲windowConfig.getSlidingLength()，而triggerHandler則爲WindowManager
TimeTriggerPolicy.start
storm-core-1.2.2-sources.jar!/org/apache/storm/windowing/TimeTriggerPolicy.java
public void start() {
executorFuture = executor.scheduleAtFixedRate(newTriggerTask(), duration, duration, TimeUnit.MILLISECONDS);
}
private Runnable newTriggerTask() {
return new Runnable() {
@Override
public void run() {
// do not process current timestamp since tuples might arrive while the trigger is executing
long now = System.currentTimeMillis() - 1;
try {
/*
* set the current timestamp as the reference time for the eviction policy
* to evict the events
*/
if (evictionPolicy != null) {
evictionPolicy.setContext(new DefaultEvictionContext(now, null, null, duration));
}
handler.onTrigger();
} catch (Throwable th) {
LOG.error("handler.onTrigger failed ", th);
/*
* propagate it so that task gets canceled and the exception
* can be retrieved from executorFuture.get()
*/
throw th;
}
}
};
}- start方法註冊了一個調度任務，每隔duration觸發(
windowConfig.getSlidingLength())；而run方法是觸發handler.onTrigger()，即WindowManager.onTrigger()
WindowManager.onTrigger
storm-core-1.2.2-sources.jar!/org/apache/storm/windowing/WindowManager.java
/**
* The callback invoked by the trigger policy.
*/
@Override
public boolean onTrigger() {
List<Event<T>> windowEvents = null;
List<T> expired = null;
try {
lock.lock();
/*
* scan the entire window to handle out of order events in
* the case of time based windows.
*/
windowEvents = scanEvents(true);
expired = new ArrayList<>(expiredEvents);
expiredEvents.clear();
} finally {
lock.unlock();
}
List<T> events = new ArrayList<>();
List<T> newEvents = new ArrayList<>();
for (Event<T> event : windowEvents) {
events.add(event.get());
if (!prevWindowEvents.contains(event)) {
newEvents.add(event.get());
}
}
prevWindowEvents.clear();
if (!events.isEmpty()) {
prevWindowEvents.addAll(windowEvents);
LOG.debug("invoking windowLifecycleListener onActivation, [{}] events in window.", events.size());
windowLifecycleListener.onActivation(events, newEvents, expired);
} else {
LOG.debug("No events in the window, skipping onActivation");
}
triggerPolicy.reset();
return !events.isEmpty();
}- 這裏調用了windowLifecycleListener.onActivation(events, newEvents, expired)，而windowLifecycleListener爲AbstractTridentWindowManager的TridentWindowLifeCycleListener
TridentWindowLifeCycleListener.onActivation
storm-core-1.2.2-sources.jar!/org/apache/storm/trident/windowing/AbstractTridentWindowManager.java
/**
* Listener to reeive any activation/expiry of windowing events and take further action on them.
*/
class TridentWindowLifeCycleListener implements WindowLifecycleListener<T> {
@Override
public void onExpiry(List<T> expiredEvents) {
LOG.debug("onExpiry is invoked");
onTuplesExpired(expiredEvents);
}
@Override
public void onActivation(List<T> events, List<T> newEvents, List<T> expired) {
LOG.debug("onActivation is invoked with events size: [{}]", events.size());
// trigger occurred, create an aggregation and keep them in store
int currentTriggerId = triggerId.incrementAndGet();
execAggregatorAndStoreResult(currentTriggerId, events);
}
}
private void execAggregatorAndStoreResult(int currentTriggerId, List<T> tupleEvents) {
List<TridentTuple> resultTuples = getTridentTuples(tupleEvents);
// run aggregator to compute the result
AccumulatedTuplesCollector collector = new AccumulatedTuplesCollector(delegateCollector);
Object state = aggregator.init(currentTriggerId, collector);
for (TridentTuple resultTuple : resultTuples) {
aggregator.aggregate(state, resultTuple, collector);
}
aggregator.complete(state, collector);
List<List<Object>> resultantAggregatedValue = collector.values;
ArrayList<WindowsStore.Entry> entries = Lists.newArrayList(new WindowsStore.Entry(windowTriggerCountId, currentTriggerId + 1),
new WindowsStore.Entry(WindowTridentProcessor.generateWindowTriggerKey(windowTaskId, currentTriggerId), resultantAggregatedValue));
windowStore.putAll(entries);
pendingTriggers.add(new TriggerResult(currentTriggerId, resultantAggregatedValue));
}- TridentWindowLifeCycleListener.onActivation方法主要是execAggregatorAndStoreResult
- 而execAggregatorAndStoreResult則依次調用aggregator的init、aggregate及complete方法
- 最後將TriggerResult放入pendingTriggers
小結
- storm在TimeTriggerPolicy.start的時候註冊了定時任務TriggerTask，以SlidingDurationWindowStrategy爲例，它的調度間隔爲windowConfig.getSlidingLength()
- TriggerTask定時觸發WindowManager.onTrigger方法，該方法會回調windowLifecycleListener.onActivation
- AbstractTridentWindowManager提供了TridentWindowLifeCycleListener，它的onActivation主要是調用execAggregatorAndStoreResult；而execAggregatorAndStoreResult方法主要完成對aggregator的一系列調用，先是調用init方法，然後遍歷resultTuples挨個調用aggregate方法，最後complete方法(
從這裏可以清晰看到Aggregator接口的各個方法的調用邏輯及順序)
doc
- Windowing Support in Core Storm