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本文次要钻研一下jedis的testWhileIdle
testWhileIdle
org/apache/commons/pool2/impl/GenericObjectPool.java
@Override public void evict() throws Exception { assertOpen(); if (!idleObjects.isEmpty()) { PooledObject<T> underTest = null; final EvictionPolicy<T> evictionPolicy = getEvictionPolicy(); synchronized (evictionLock) { final EvictionConfig evictionConfig = new EvictionConfig( getMinEvictableIdleDuration(), getSoftMinEvictableIdleDuration(), getMinIdle()); final boolean testWhileIdle = getTestWhileIdle(); for (int i = 0, m = getNumTests(); i < m; i++) { if (evictionIterator == null || !evictionIterator.hasNext()) { evictionIterator = new EvictionIterator(idleObjects); } if (!evictionIterator.hasNext()) { // Pool exhausted, nothing to do here return; } try { underTest = evictionIterator.next(); } catch (final NoSuchElementException nsee) { // Object was borrowed in another thread // Don't count this as an eviction test so reduce i; i--; evictionIterator = null; continue; } if (!underTest.startEvictionTest()) { // Object was borrowed in another thread // Don't count this as an eviction test so reduce i; i--; continue; } // User provided eviction policy could throw all sorts of // crazy exceptions. Protect against such an exception // killing the eviction thread. boolean evict; try { evict = evictionPolicy.evict(evictionConfig, underTest, idleObjects.size()); } catch (final Throwable t) { // Slightly convoluted as SwallowedExceptionListener // uses Exception rather than Throwable PoolUtils.checkRethrow(t); swallowException(new Exception(t)); // Don't evict on error conditions evict = false; } if (evict) { destroy(underTest, DestroyMode.NORMAL); destroyedByEvictorCount.incrementAndGet(); } else { if (testWhileIdle) { boolean active = false; try { factory.activateObject(underTest); active = true; } catch (final Exception e) { destroy(underTest, DestroyMode.NORMAL); destroyedByEvictorCount.incrementAndGet(); } if (active) { boolean validate = false; Throwable validationThrowable = null; try { validate = factory.validateObject(underTest); } catch (final Throwable t) { PoolUtils.checkRethrow(t); validationThrowable = t; } if (!validate) { destroy(underTest, DestroyMode.NORMAL); destroyedByEvictorCount.incrementAndGet(); if (validationThrowable != null) { if (validationThrowable instanceof RuntimeException) { throw (RuntimeException) validationThrowable; } throw (Error) validationThrowable; } } else { try { factory.passivateObject(underTest); } catch (final Exception e) { destroy(underTest, DestroyMode.NORMAL); destroyedByEvictorCount.incrementAndGet(); } } } } if (!underTest.endEvictionTest(idleObjects)) { // TODO - May need to add code here once additional // states are used } } } } } final AbandonedConfig ac = this.abandonedConfig; if (ac != null && ac.getRemoveAbandonedOnMaintenance()) { removeAbandoned(ac); } }GenericObjectPool的evict办法在idleObjects不为空的时候会执行evict逻辑，它先通过getNumTests获取每次要对多少个idleObject进行验证，之后循环解决，首先通过evictionPolicy.evict判断是否须要evict，如果是则执行destroy办法，否则判断是否testWhileIdle，若是则先执行activateObject办法，再执行validateObject，如果activateObject或者validateObject失败则执行destroy办法，如果validateObject胜利则执行passivateObject办法
JedisFactory
redis/clients/jedis/JedisFactory.java
@Override public void activateObject(PooledObject<Jedis> pooledJedis) throws Exception { final BinaryJedis jedis = pooledJedis.getObject(); if (jedis.getDB() != clientConfig.getDatabase()) { jedis.select(clientConfig.getDatabase()); } } @Override public boolean validateObject(PooledObject<Jedis> pooledJedis) { final BinaryJedis jedis = pooledJedis.getObject(); try { String host = jedisSocketFactory.getHost(); int port = jedisSocketFactory.getPort(); String connectionHost = jedis.getClient().getHost(); int connectionPort = jedis.getClient().getPort(); return host.equals(connectionHost) && port == connectionPort && jedis.isConnected() && jedis.ping().equals("PONG"); } catch (final Exception e) { logger.error("Error while validating pooled Jedis object.", e); return false; } } @Override public void passivateObject(PooledObject<Jedis> pooledJedis) throws Exception { // TODO maybe should select db 0? Not sure right now. } @Override public void destroyObject(PooledObject<Jedis> pooledJedis) throws Exception { final BinaryJedis jedis = pooledJedis.getObject(); if (jedis.isConnected()) { try { // need a proper test, probably with mock if (!jedis.isBroken()) { jedis.quit(); } } catch (RuntimeException e) { logger.warn("Error while QUIT", e); } try { jedis.close(); } catch (RuntimeException e) { logger.warn("Error while close", e); } } }JedisFactory的activateObject判断db是否一样，不一样则执行select办法；validateObject办法则执行ping；passivateObject办法为空操作；destroyObject办法会判断是否broken，非broken执行quit，最初执行close办法
Evictor
org/apache/commons/pool2/impl/BaseGenericObjectPool.java
/** * The idle object evictor {@link TimerTask}. * * @see GenericKeyedObjectPool#setTimeBetweenEvictionRunsMillis */ class Evictor implements Runnable { private ScheduledFuture<?> scheduledFuture; /** * Cancels the scheduled future. */ void cancel() { scheduledFuture.cancel(false); } /** * Run pool maintenance. Evict objects qualifying for eviction and then * ensure that the minimum number of idle instances are available. * Since the Timer that invokes Evictors is shared for all Pools but * pools may exist in different class loaders, the Evictor ensures that * any actions taken are under the class loader of the factory * associated with the pool. */ @Override public void run() { final ClassLoader savedClassLoader = Thread.currentThread().getContextClassLoader(); try { if (factoryClassLoader != null) { // Set the class loader for the factory final ClassLoader cl = factoryClassLoader.get(); if (cl == null) { // The pool has been dereferenced and the class loader // GC'd. Cancel this timer so the pool can be GC'd as // well. cancel(); return; } Thread.currentThread().setContextClassLoader(cl); } // Evict from the pool try { evict(); } catch(final Exception e) { swallowException(e); } catch(final OutOfMemoryError oome) { // Log problem but give evictor thread a chance to continue // in case error is recoverable oome.printStackTrace(System.err); } // Re-create idle instances. try { ensureMinIdle(); } catch (final Exception e) { swallowException(e); } } finally { // Restore the previous CCL Thread.currentThread().setContextClassLoader(savedClassLoader); } } /** * Sets the scheduled future. * * @param scheduledFuture the scheduled future. */ void setScheduledFuture(final ScheduledFuture<?> scheduledFuture) { this.scheduledFuture = scheduledFuture; } }Evictor实现了Runnable办法，其run办法先执行evict办法，后执行ensureMinIdle办法
setTimeBetweenEvictionRuns
org/apache/commons/pool2/impl/BaseGenericObjectPool.java
/** * Sets the number of milliseconds to sleep between runs of the idle object evictor thread. * <ul> * <li>When positive, the idle object evictor thread starts.</li> * <li>When non-positive, no idle object evictor thread runs.</li> * </ul> * * @param timeBetweenEvictionRuns * duration to sleep between evictor runs * * @see #getTimeBetweenEvictionRunsMillis * @since 2.10.0 */ public final void setTimeBetweenEvictionRuns(final Duration timeBetweenEvictionRuns) { this.durationBetweenEvictionRuns = PoolImplUtils.nonNull(timeBetweenEvictionRuns, BaseObjectPoolConfig.DEFAULT_TIME_BETWEEN_EVICTION_RUNS); startEvictor(this.durationBetweenEvictionRuns); }setTimeBetweenEvictionRuns办法会给durationBetweenEvictionRuns赋值，同时执行startEvictor办法
startEvictor
org/apache/commons/pool2/impl/BaseGenericObjectPool.java
/** * <p>Starts the evictor with the given delay. If there is an evictor * running when this method is called, it is stopped and replaced with a * new evictor with the specified delay.</p> * * <p>This method needs to be final, since it is called from a constructor. * See POOL-195.</p> * * @param delay time in milliseconds before start and between eviction runs */ final void startEvictor(final Duration delay) { synchronized (evictionLock) { final boolean isPositiverDelay = PoolImplUtils.isPositive(delay); if (evictor == null) { // Starting evictor for the first time or after a cancel if (isPositiverDelay) { // Starting new evictor evictor = new Evictor(); EvictionTimer.schedule(evictor, delay, delay); } } else if (isPositiverDelay) { // Stop or restart of existing evictor: Restart synchronized (EvictionTimer.class) { // Ensure no cancel can happen between cancel / schedule calls EvictionTimer.cancel(evictor, evictorShutdownTimeoutDuration, true); evictor = null; evictionIterator = null; evictor = new Evictor(); EvictionTimer.schedule(evictor, delay, delay); } } else { // Stopping evictor EvictionTimer.cancel(evictor, evictorShutdownTimeoutDuration, false); } } }startEvictor办法会判断delay是否是负数，是的话，则执行EvictionTimer.schedule(evictor, delay, delay)，不是则执行EvictionTimer.cancel(evictor, evictorShutdownTimeoutDuration, false)；对于evictor不为null的会先执行cancel再执行schedule
EvictionTimer
org/apache/commons/pool2/impl/EvictionTimer.java
/** * Adds the specified eviction task to the timer. Tasks that are added with * a call to this method *must* call {@link * #cancel(BaseGenericObjectPool.Evictor, Duration, boolean)} * to cancel the task to prevent memory and/or thread leaks in application * server environments. * * @param task Task to be scheduled. * @param delay Delay in milliseconds before task is executed. * @param period Time in milliseconds between executions. */ static synchronized void schedule( final BaseGenericObjectPool<?>.Evictor task, final Duration delay, final Duration period) { if (null == executor) { executor = new ScheduledThreadPoolExecutor(1, new EvictorThreadFactory()); executor.setRemoveOnCancelPolicy(true); executor.scheduleAtFixedRate(new Reaper(), delay.toMillis(), period.toMillis(), TimeUnit.MILLISECONDS); } final WeakReference<Runnable> ref = new WeakReference<>(task); final WeakRunner runner = new WeakRunner(ref); final ScheduledFuture<?> scheduledFuture = executor.scheduleWithFixedDelay(runner, delay.toMillis(), period.toMillis(), TimeUnit.MILLISECONDS); task.setScheduledFuture(scheduledFuture); taskMap.put(ref, runner); }schedule办法应用的是ScheduledThreadPoolExecutor的scheduleWithFixedDelay办法来执行evictor；而再executor为null时会创立ScheduledThreadPoolExecutor，同时触发scheduleAtFixedRate来执行Reaper
Reaper
org/apache/commons/pool2/impl/EvictionTimer.java
/** * Task that removes references to abandoned tasks and shuts * down the executor if there are no live tasks left. */ private static class Reaper implements Runnable { @Override public void run() { synchronized (EvictionTimer.class) { for (final Entry<WeakReference<Runnable>, WeakRunner> entry : taskMap.entrySet()) { if (entry.getKey().get() == null) { executor.remove(entry.getValue()); taskMap.remove(entry.getKey()); } } if (taskMap.isEmpty() && executor != null) { executor.shutdown(); executor.setCorePoolSize(0); executor = null; } } } }Reaper次要是遍历taskMap，删除被cancel掉的task
小结
jedis的testWhileIdle是依赖Evictor来进行的，即Evictor它通过evictionPolicy.evict判断是否须要evict，如果是则执行evict逻辑，即destroy办法，否则走testWhileIdle的逻辑。testWhileIdle先执行activateObject办法，再执行validateObject，如果activateObject或者validateObject失败则执行destroy办法，最初如果validateObject胜利则执行passivateObject办法。
Evictor实现了Runnable办法，其run办法先执行evict办法，后执行ensureMinIdle办法；BaseGenericObjectPool的setTimeBetweenEvictionRuns办法会给durationBetweenEvictionRuns赋值，同时执行startEvictor办法，即触发执行EvictionTimer.schedule(evictor, delay, delay)，schedule办法应用的是ScheduledThreadPoolExecutor的scheduleWithFixedDelay办法来执行evictor。
doc
- GenericObjectPool参数解析