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本文主要研究一下dubbo的EagerThreadPool
EagerThreadPool
dubbo-2.7.2/dubbo-common/src/main/java/org/apache/dubbo/common/threadpool/support/eager/EagerThreadPool.java
public class EagerThreadPool implements ThreadPool {
@Override
public Executor getExecutor(URL url) {
String name = url.getParameter(THREAD_NAME_KEY, DEFAULT_THREAD_NAME);
int cores = url.getParameter(CORE_THREADS_KEY, DEFAULT_CORE_THREADS);
int threads = url.getParameter(THREADS_KEY, Integer.MAX_VALUE);
int queues = url.getParameter(QUEUES_KEY, DEFAULT_QUEUES);
int alive = url.getParameter(ALIVE_KEY, DEFAULT_ALIVE);
// init queue and executor
TaskQueue taskQueue = new TaskQueue(queues <= 0 ? 1 : queues);
EagerThreadPoolExecutor executor = new EagerThreadPoolExecutor(cores,
threads,
alive,
TimeUnit.MILLISECONDS,
taskQueue,
new NamedInternalThreadFactory(name, true),
new AbortPolicyWithReport(name, url));
taskQueue.setExecutor(executor);
return executor;
}
} - EagerThreadPool实现了ThreadPool接口，其getExecutor创建的是EagerThreadPoolExecutor，它使用的queue为TaskQueue，使用的threadFactory为NamedInternalThreadFactory，使用的rejectedExecutionHandler为AbortPolicyWithReport
EagerThreadPoolExecutor
dubbo-2.7.2/dubbo-common/src/main/java/org/apache/dubbo/common/threadpool/support/eager/EagerThreadPoolExecutor.java
public class EagerThreadPoolExecutor extends ThreadPoolExecutor {
/**
* task count
*/
private final AtomicInteger submittedTaskCount = new AtomicInteger(0);
public EagerThreadPoolExecutor(int corePoolSize,
int maximumPoolSize,
long keepAliveTime,
TimeUnit unit, TaskQueue workQueue,
ThreadFactory threadFactory,
RejectedExecutionHandler handler) {
super(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue, threadFactory, handler);
}
/**
* @return current tasks which are executed
*/
public int getSubmittedTaskCount() {
return submittedTaskCount.get();
}
@Override
protected void afterExecute(Runnable r, Throwable t) {
submittedTaskCount.decrementAndGet();
}
@Override
public void execute(Runnable command) {
if (command == null) {
throw new NullPointerException();
}
// do not increment in method beforeExecute!
submittedTaskCount.incrementAndGet();
try {
super.execute(command);
} catch (RejectedExecutionException rx) {
// retry to offer the task into queue.
final TaskQueue queue = (TaskQueue) super.getQueue();
try {
if (!queue.retryOffer(command, 0, TimeUnit.MILLISECONDS)) {
submittedTaskCount.decrementAndGet();
throw new RejectedExecutionException("Queue capacity is full.", rx);
}
} catch (InterruptedException x) {
submittedTaskCount.decrementAndGet();
throw new RejectedExecutionException(x);
}
} catch (Throwable t) {
// decrease any way
submittedTaskCount.decrementAndGet();
throw t;
}
}
} - EagerThreadPoolExecutor继承了ThreadPoolExecutor，它维护了submittedTaskCount，在执行任务之前递增，在afterExecute的时候胡递减；其execute方法会捕获RejectedExecutionException，然后使用TaskQueue的retryOffer再重新入队，入队不成功才抛出RejectedExecutionException
TaskQueue
dubbo-2.7.2/dubbo-common/src/main/java/org/apache/dubbo/common/threadpool/support/eager/TaskQueue.java
public class TaskQueue extends LinkedBlockingQueue {
private static final long serialVersionUID = -2635853580887179627L;
private EagerThreadPoolExecutor executor;
public TaskQueue(int capacity) {
super(capacity);
}
public void setExecutor(EagerThreadPoolExecutor exec) {
executor = exec;
}
@Override
public boolean offer(Runnable runnable) {
if (executor == null) {
throw new RejectedExecutionException("The task queue does not have executor!");
}
int currentPoolThreadSize = executor.getPoolSize();
// have free worker. put task into queue to let the worker deal with task.
if (executor.getSubmittedTaskCount() < currentPoolThreadSize) {
return super.offer(runnable);
}
// return false to let executor create new worker.
if (currentPoolThreadSize < executor.getMaximumPoolSize()) {
return false;
}
// currentPoolThreadSize >= max
return super.offer(runnable);
}
/**
* retry offer task
*
* @param o task
* @return offer success or not
* @throws RejectedExecutionException if executor is terminated.
*/
public boolean retryOffer(Runnable o, long timeout, TimeUnit unit) throws InterruptedException {
if (executor.isShutdown()) {
throw new RejectedExecutionException("Executor is shutdown!");
}
return super.offer(o, timeout, unit);
}
} - TaskQueue继承了LinkedBlockingQueue，它覆盖了offer方法，该方法在submittedTaskCount小于poolSize的时候会入队，如果大于等于poolSize则再判断currentPoolThreadSize是否小于maximumPoolSize，如果小于则返回false让线程池创建新线程，最后在currentPoolThreadSize大于等于maximumPoolSize的时候入队
NamedInternalThreadFactory
dubbo-2.7.2/dubbo-common/src/main/java/org/apache/dubbo/common/threadlocal/NamedInternalThreadFactory.java
public class NamedInternalThreadFactory extends NamedThreadFactory {
public NamedInternalThreadFactory() {
super();
}
public NamedInternalThreadFactory(String prefix) {
super(prefix, false);
}
public NamedInternalThreadFactory(String prefix, boolean daemon) {
super(prefix, daemon);
}
@Override
public Thread newThread(Runnable runnable) {
String name = mPrefix + mThreadNum.getAndIncrement();
InternalThread ret = new InternalThread(mGroup, runnable, name, 0);
ret.setDaemon(mDaemon);
return ret;
}
}- NamedInternalThreadFactory继承了NamedThreadFactory，这里创建的是InternalThread
AbortPolicyWithReport
dubbo-2.7.2/dubbo-common/src/main/java/org/apache/dubbo/common/threadpool/support/AbortPolicyWithReport.java
public class AbortPolicyWithReport extends ThreadPoolExecutor.AbortPolicy {
protected static final Logger logger = LoggerFactory.getLogger(AbortPolicyWithReport.class);
private final String threadName;
private final URL url;
private static volatile long lastPrintTime = 0;
private static final long TEN_MINUTES_MILLS = 10 * 60 * 1000;
private static final String OS_WIN_PREFIX = "win";
private static final String OS_NAME_KEY = "os.name";
private static final String WIN_DATETIME_FORMAT = "yyyy-MM-dd_HH-mm-ss";
private static final String DEFAULT_DATETIME_FORMAT = "yyyy-MM-dd_HH:mm:ss";
private static Semaphore guard = new Semaphore(1);
public AbortPolicyWithReport(String threadName, URL url) {
this.threadName = threadName;
this.url = url;
}
@Override
public void rejectedExecution(Runnable r, ThreadPoolExecutor e) {
String msg = String.format("Thread pool is EXHAUSTED!" +
" Thread Name: %s, Pool Size: %d (active: %d, core: %d, max: %d, largest: %d), Task: %d (completed: "
+ "%d)," +
" Executor status:(isShutdown:%s, isTerminated:%s, isTerminating:%s), in %s://%s:%d!",
threadName, e.getPoolSize(), e.getActiveCount(), e.getCorePoolSize(), e.getMaximumPoolSize(),
e.getLargestPoolSize(),
e.getTaskCount(), e.getCompletedTaskCount(), e.isShutdown(), e.isTerminated(), e.isTerminating(),
url.getProtocol(), url.getIp(), url.getPort());
logger.warn(msg);
dumpJStack();
throw new RejectedExecutionException(msg);
}
private void dumpJStack() {
long now = System.currentTimeMillis();
//dump every 10 minutes
if (now - lastPrintTime < TEN_MINUTES_MILLS) {
return;
}
if (!guard.tryAcquire()) {
return;
}
ExecutorService pool = Executors.newSingleThreadExecutor();
pool.execute(() -> {
String dumpPath = url.getParameter(DUMP_DIRECTORY, System.getProperty("user.home"));
SimpleDateFormat sdf;
String os = System.getProperty(OS_NAME_KEY).toLowerCase();
// window system don't support ":" in file name
if (os.contains(OS_WIN_PREFIX)) {
sdf = new SimpleDateFormat(WIN_DATETIME_FORMAT);
} else {
sdf = new SimpleDateFormat(DEFAULT_DATETIME_FORMAT);
}
String dateStr = sdf.format(new Date());
//try-with-resources
try (FileOutputStream jStackStream = new FileOutputStream(
new File(dumpPath, "Dubbo_JStack.log" + "." + dateStr))) {
JVMUtil.jstack(jStackStream);
} catch (Throwable t) {
logger.error("dump jStack error", t);
} finally {
guard.release();
}
lastPrintTime = System.currentTimeMillis();
});
//must shutdown thread pool ,if not will lead to OOM
pool.shutdown();
}
}- AbortPolicyWithReport继承了ThreadPoolExecutor.AbortPolicy，其rejectedExecution方法会输出包含thread pool相关信息的msg，然后使用warn级别打印出来，然后进行dumpJStack，最后再抛出RejectedExecutionException
小结
EagerThreadPool实现了ThreadPool接口，其getExecutor创建的是EagerThreadPoolExecutor，它使用的queue为TaskQueue，使用的threadFactory为NamedInternalThreadFactory，使用的rejectedExecutionHandler为AbortPolicyWithReport
doc
- EagerThreadPool