企业搜索引擎开发之连接器connector（十四）
回顾Context类的start方法，还有一部分是启动调度器的方法
/** * Start up the Scheduler. */ private void startScheduler() { traversalScheduler = (TraversalScheduler) getRequiredBean("TraversalScheduler", TraversalScheduler.class); if (traversalScheduler != null) { traversalScheduler.init(); } }
即执行TraversalScheduler类对象的init()方法
TraversalScheduler是实现Runnable接口的类，实现该接口的多线程方法，其源码如下：
/** * Scheduler that schedules connector traversal. This class is thread safe. * Must initialize TraversalScheduler before running it. * * <p> This facility includes a schedule thread that runs a loop. * Each iteration it asks the instantiator for the schedule * for each Connector Instance and runs batches for those that * are * <OL> * <LI> scheduled to run. * <LI> have not exhausted their quota for the current time interval. * <LI> are not currently running. * </OL> * The implementation must handle the situation that a Connector * Instance is running. */ public class TraversalScheduler implements Runnable { public static final String SCHEDULER_CURRENT_TIME = "/Scheduler/currentTime"; private static final Logger LOGGER = Logger.getLogger(TraversalScheduler.class.getName()); private final Instantiator instantiator; private boolean isInitialized; // Protected by instance lock. private boolean isShutdown; // Protected by instance lock. /** * Create a scheduler object. * * @param instantiator used to get schedule for connector instances */ public TraversalScheduler(Instantiator instantiator) { this.instantiator = instantiator; this.isInitialized = false; this.isShutdown = false; } public synchronized void init() { if (isInitialized) { return; } isInitialized = true; isShutdown = false; new Thread(this, "TraversalScheduler").start(); } public synchronized void shutdown() { if (isShutdown) { return; } isInitialized = false; isShutdown = true; } /** * Determines whether scheduler should run. * * @return true if we are in a running state and scheduler should run or * continue running. */ private synchronized boolean isRunningState() { return isInitialized && !isShutdown; } private void scheduleBatches() { for (String connectorName : instantiator.getConnectorNames()) { NDC.pushAppend(connectorName); try { instantiator.getConnectorCoordinator(connectorName).startBatch(); } catch (ConnectorNotFoundException e) { // Looks like the connector just got deleted. Don't schedule it. } finally { NDC.pop(); } } } public void run() { NDC.push("Traverse"); try { while (true) { try { if (!isRunningState()) { LOGGER.info("TraversalScheduler thread is stopping due to " + "shutdown or not being initialized."); return; } scheduleBatches(); // Give someone else a chance to run. try { synchronized (this) { wait(1000); } } catch (InterruptedException e) { // May have been interrupted for shutdown. } } catch (Throwable t) { LOGGER.log(Level.SEVERE, "TraversalScheduler caught unexpected Throwable: ", t); } } } finally { NDC.remove(); } } }
TraversalScheduler类依赖于Instantiator类，用于Instantiator遍历所有连接器的ConnectorCoordinatorImpl对象并启用startBatch()方法
多线程实现方法run()里面是一个死循环，不断的轮询执行scheduleBatches()方法
我们回顾前面的ConnectorCoordinatorImpl类的startBatch()方法
//@Override public synchronized boolean startBatch() throws ConnectorNotFoundException { verifyConnectorInstanceAvailable(); if (!shouldRun()) { return false; } BatchSize batchSize = loadManager.determineBatchSize(); if (batchSize.getMaximum() == 0) { return false; } taskHandle = null; currentBatchKey = new Object(); try { BatchCoordinator batchCoordinator = new BatchCoordinator(this); TraversalManager traversalManager = getConnectorInterfaces().getTraversalManager(); Traverser traverser = new QueryTraverser(pusherFactory, traversalManager, batchCoordinator, name, Context.getInstance().getTraversalContext()); TimedCancelable batch = new CancelableBatch(traverser, name, batchCoordinator, batchCoordinator, batchSize); taskHandle = threadPool.submit(batch); return true; } catch (ConnectorNotFoundException cnfe) { LOGGER.log(Level.WARNING, "Connector not found - this is normal if you " + " recently reconfigured your connector instance: " + cnfe); } catch (InstantiatorException ie) { LOGGER.log(Level.WARNING, "Failed to perform connector content traversal.", ie); delayTraversal(TraversalDelayPolicy.ERROR); } return false; }
方法首先执行!shouldRun()的判断，我们分析一下该方法的源码：
/** * Returns {@code true} if it is OK to start a traversal, * {@code false} otherwise. */ // Package access because this is called by tests. synchronized boolean shouldRun() { // Are we already running? If so, we shouldn't run again. if (taskHandle != null && !taskHandle.isDone()) { return false; } // Don't run if we have postponed traversals. if (System.currentTimeMillis() < traversalDelayEnd) { return false; } Schedule schedule = getSchedule(); // Don't run if traversals are disabled. if (schedule.isDisabled()) { return false; } // Don't run if we have exceeded our configured host load. if (loadManager.shouldDelay()) { return false; } // OK to run if we are within one of the Schedule's traversal intervals. Calendar now = Calendar.getInstance(); int hour = now.get(Calendar.HOUR_OF_DAY); for (ScheduleTimeInterval interval : schedule.getTimeIntervals()) { int startHour = interval.getStartTime().getHour(); int endHour = interval.getEndTime().getHour(); if (0 == endHour) { endHour = 24; } if (endHour < startHour) { // The traversal interval straddles midnight. if ((hour >= startHour) || (hour < endHour)) { return true; } } else { // The traversal interval falls wholly within the day. if ((hour >= startHour) && (hour < endHour)) { return true; } } } return false; }
该方法对是否调度连接器做出审查，如上轮调度是否完成、调度设置是否可用、加载管理器是否要求延迟、调度时机是否成熟等
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本系列企业搜索引擎开发之连接器connector系本人原创
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本文链接 http://www.cnblogs.com/chenying99/archive/2013/03/20/2970378.html