/**
* Copyright 2012 Netflix, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.netflix.hystrix;
import com.netflix.hystrix.strategy.HystrixPlugins;
import com.netflix.hystrix.strategy.concurrency.HystrixConcurrencyStrategy;
import com.netflix.hystrix.strategy.concurrency.HystrixContextScheduler;
import com.netflix.hystrix.strategy.metrics.HystrixMetricsPublisherFactory;
import com.netflix.hystrix.strategy.properties.HystrixPropertiesFactory;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import rx.Scheduler;
import rx.functions.Func0;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
/**
* ThreadPool used to executed {@link HystrixCommand#run()} on separate threads when configured to do so with {@link HystrixCommandProperties#executionIsolationStrategy()}.
* <p>
* Typically each {@link HystrixCommandGroupKey} has its own thread-pool so that any one group of commands can not starve others from being able to run.
* <p>
* A {@link HystrixCommand} can be configured with a thread-pool explicitly by injecting a {@link HystrixThreadPoolKey} or via the
* {@link HystrixCommandProperties#executionIsolationThreadPoolKeyOverride()} otherwise it
* will derive a {@link HystrixThreadPoolKey} from the injected {@link HystrixCommandGroupKey}.
* <p>
* The pool should be sized large enough to handle normal healthy traffic but small enough that it will constrain concurrent execution if backend calls become latent.
* <p>
* For more information see the Github Wiki: https://github.com/Netflix/Hystrix/wiki/Configuration#wiki-ThreadPool and https://github.com/Netflix/Hystrix/wiki/How-it-Works#wiki-Isolation
*/
public interface HystrixThreadPool {
/**
* Implementation of {@link ThreadPoolExecutor}.
*
* @return ThreadPoolExecutor
*/
public ExecutorService getExecutor();
public Scheduler getScheduler();
public Scheduler getScheduler(Func0<Boolean> shouldInterruptThread);
/**
* Mark when a thread begins executing a command.
*/
public void markThreadExecution();
/**
* Mark when a thread completes executing a command.
*/
public void markThreadCompletion();
/**
* Mark when a command gets rejected from the threadpool
*/
public void markThreadRejection();
/**
* Whether the queue will allow adding an item to it.
* <p>
* This allows dynamic control of the max queueSize versus whatever the actual max queueSize is so that dynamic changes can be done via property changes rather than needing an app
* restart to adjust when commands should be rejected from queuing up.
*
* @return boolean whether there is space on the queue
*/
public boolean isQueueSpaceAvailable();
/**
* @ExcludeFromJavadoc
*/
/* package */static class Factory {
/*
* Use the String from HystrixThreadPoolKey.name() instead of the HystrixThreadPoolKey instance as it's just an interface and we can't ensure the object
* we receive implements hashcode/equals correctly and do not want the default hashcode/equals which would create a new threadpool for every object we get even if the name is the same
*/
/* package */final static ConcurrentHashMap<String, HystrixThreadPool> threadPools = new ConcurrentHashMap<String, HystrixThreadPool>();
/**
* Get the {@link HystrixThreadPool} instance for a given {@link HystrixThreadPoolKey}.
* <p>
* This is thread-safe and ensures only 1 {@link HystrixThreadPool} per {@link HystrixThreadPoolKey}.
*
* @return {@link HystrixThreadPool} instance
*/
/* package */static HystrixThreadPool getInstance(HystrixThreadPoolKey threadPoolKey, HystrixThreadPoolProperties.Setter propertiesBuilder) {
// get the key to use instead of using the object itself so that if people forget to implement equals/hashcode things will still work
String key = threadPoolKey.name();
// this should find it for all but the first time
HystrixThreadPool previouslyCached = threadPools.get(key);
if (previouslyCached != null) {
return previouslyCached;
}
// if we get here this is the first time so we need to initialize
synchronized (HystrixThreadPool.class) {
if (!threadPools.containsKey(key)) {
threadPools.put(key, new HystrixThreadPoolDefault(threadPoolKey, propertiesBuilder));
}
}
return threadPools.get(key);
}
/**
* Initiate the shutdown of all {@link HystrixThreadPool} instances.
* <p>
* NOTE: This is NOT thread-safe if HystrixCommands are concurrently being executed
* and causing thread-pools to initialize while also trying to shutdown.
* </p>
*/
/* package */static synchronized void shutdown() {
for (HystrixThreadPool pool : threadPools.values()) {
pool.getExecutor().shutdown();
}
threadPools.clear();
}
/**
* Initiate the shutdown of all {@link HystrixThreadPool} instances and wait up to the given time on each pool to complete.
* <p>
* NOTE: This is NOT thread-safe if HystrixCommands are concurrently being executed
* and causing thread-pools to initialize while also trying to shutdown.
* </p>
*/
/* package */static synchronized void shutdown(long timeout, TimeUnit unit) {
for (HystrixThreadPool pool : threadPools.values()) {
pool.getExecutor().shutdown();
}
for (HystrixThreadPool pool : threadPools.values()) {
try {
while (! pool.getExecutor().awaitTermination(timeout, unit)) {
}
} catch (InterruptedException e) {
throw new RuntimeException("Interrupted while waiting for thread-pools to terminate. Pools may not be correctly shutdown or cleared.", e);
}
}
threadPools.clear();
}
}
/**
* @ExcludeFromJavadoc
* @ThreadSafe
*/
/* package */static class HystrixThreadPoolDefault implements HystrixThreadPool {
private static final Logger logger = LoggerFactory.getLogger(HystrixThreadPoolDefault.class);
private final HystrixThreadPoolProperties properties;
private final BlockingQueue<Runnable> queue;
private final ThreadPoolExecutor threadPool;
private final HystrixThreadPoolMetrics metrics;
private final int queueSize;
public HystrixThreadPoolDefault(HystrixThreadPoolKey threadPoolKey, HystrixThreadPoolProperties.Setter propertiesDefaults) {
this.properties = HystrixPropertiesFactory.getThreadPoolProperties(threadPoolKey, propertiesDefaults);
HystrixConcurrencyStrategy concurrencyStrategy = HystrixPlugins.getInstance().getConcurrencyStrategy();
this.queueSize = properties.maxQueueSize().get();
this.metrics = HystrixThreadPoolMetrics.getInstance(threadPoolKey,
concurrencyStrategy.getThreadPool(threadPoolKey, properties),
properties);
this.threadPool = this.metrics.getThreadPool();
this.queue = this.threadPool.getQueue();
/* strategy: HystrixMetricsPublisherThreadPool */
HystrixMetricsPublisherFactory.createOrRetrievePublisherForThreadPool(threadPoolKey, this.metrics, this.properties);
}
@Override
public ThreadPoolExecutor getExecutor() {
touchConfig();
return threadPool;
}
@Override
public Scheduler getScheduler() {
//by default, interrupt underlying threads on timeout
return getScheduler(new Func0<Boolean>() {
@Override
public Boolean call() {
return true;
}
});
}
@Override
public Scheduler getScheduler(Func0<Boolean> shouldInterruptThread) {
touchConfig();
return new HystrixContextScheduler(HystrixPlugins.getInstance().getConcurrencyStrategy(), this, shouldInterruptThread);
}
// allow us to change things via fast-properties by setting it each time
private void touchConfig() {
final int dynamicCoreSize = properties.coreSize().get();
final int configuredMaximumSize = properties.maximumSize().get();
int dynamicMaximumSize = properties.actualMaximumSize();
final boolean allowSizesToDiverge = properties.getAllowMaximumSizeToDivergeFromCoreSize().get();
boolean maxTooLow = false;
if (allowSizesToDiverge && configuredMaximumSize < dynamicCoreSize) {
//if user sets maximum < core (or defaults get us there), we need to maintain invariant of core <= maximum
dynamicMaximumSize = dynamicCoreSize;
maxTooLow = true;
}
// In JDK 6, setCorePoolSize and setMaximumPoolSize will execute a lock operation. Avoid them if the pool size is not changed.
if (threadPool.getCorePoolSize() != dynamicCoreSize || (allowSizesToDiverge && threadPool.getMaximumPoolSize() != dynamicMaximumSize)) {
if (maxTooLow) {
logger.error("Hystrix ThreadPool configuration for : " + metrics.getThreadPoolKey().name() + " is trying to set coreSize = " +
dynamicCoreSize + " and maximumSize = " + configuredMaximumSize + ". Maximum size will be set to " +
dynamicMaximumSize + ", the coreSize value, since it must be equal to or greater than the coreSize value");
}
threadPool.setCorePoolSize(dynamicCoreSize);
threadPool.setMaximumPoolSize(dynamicMaximumSize);
}
threadPool.setKeepAliveTime(properties.keepAliveTimeMinutes().get(), TimeUnit.MINUTES);
}
@Override
public void markThreadExecution() {
metrics.markThreadExecution();
}
@Override
public void markThreadCompletion() {
metrics.markThreadCompletion();
}
@Override
public void markThreadRejection() {
metrics.markThreadRejection();
}
/**
* Whether the threadpool queue has space available according to the <code>queueSizeRejectionThreshold</code> settings.
*
* Note that the <code>queueSize</code> is an final instance variable on HystrixThreadPoolDefault, and not looked up dynamically.
* The data structure is static, so this does not make sense as a dynamic lookup.
* The <code>queueSizeRejectionThreshold</code> can be dynamic (up to <code>queueSize</code>), so that should
* still get checked on each invocation.
* <p>
* If a SynchronousQueue implementation is used (<code>maxQueueSize</code> <= 0), it always returns 0 as the size so this would always return true.
*/
@Override
public boolean isQueueSpaceAvailable() {
if (queueSize <= 0) {
// we don't have a queue so we won't look for space but instead
// let the thread-pool reject or not
return true;
} else {
return threadPool.getQueue().size() < properties.queueSizeRejectionThreshold().get();
}
}
}
}