Package com.google.apphosting.runtime

Class ThreadGroupPool

java.lang.Object

com.google.apphosting.runtime.ThreadGroupPool

public class ThreadGroupPool
extends Object

ThreadGroupPool is a very simple thread pool where each pooled thread is in its own ThreadGroup. Unfortunately threads cannot be moved around between thread groups, so we just pool (ThreadGroup, Thread) pairs. If additional threads are started in a thread group, they are expected to have exited before the runnable provided to start(java.lang.String, java.lang.Runnable) completes. If this is not the case, the thread will be dropped from the thread pool and detailed diagnostics will be written to the log.

Unlike thread names, thread group names are immutable so thread groups will be named with a specified prefix with a counter appended. The name of the main thread for each thread pool is determined when start(java.lang.String, java.lang.Runnable) is called.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	ThreadGroupPool.Builder	Builder for ThreadGroupPool.

Constructor Summary

Constructors

Constructor	Description
ThreadGroupPool(ThreadGroup parentThreadGroup, String threadGroupNamePrefix, Thread.UncaughtExceptionHandler uncaughtExceptionHandler, boolean ignoreDaemonThreads)

Method Summary

Modifier and Type	Method	Description
static ThreadGroupPool.Builder	builder()
static CountDownLatch	resetCurrentThread()	If the current thread is main thread started in response to a call to start(java.lang.String, java.lang.Runnable), this method will arrange for it to expect to be "restarted."
void	start(String threadName, Runnable runnable)	Execute runnable in a thread named threadName.
int	waitingThreadCount()

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details

ThreadGroupPool

public ThreadGroupPool(ThreadGroup parentThreadGroup,
 String threadGroupNamePrefix,
 Thread.UncaughtExceptionHandler uncaughtExceptionHandler,
 boolean ignoreDaemonThreads)

Method Details

builder

public static ThreadGroupPool.Builder builder()

start

public void start(String threadName,
 Runnable runnable)
           throws InterruptedException

Execute runnable in a thread named threadName. This may be a newly created thread or it may be a thread that was was already used to run one or more previous invocations.

runnable can spawn other threads in the pooled ThreadGroup, but they must all exit before the runnable completes. Failure of the extra threads to complete will result in a severe log message and the dropping of this thread from the pool.

This method will block until the thread begins executing runnable. If executing Runnable.run() on runnable throws an exception, the thread will not be returned to the thread pool.

Throws:

InterruptedException

waitingThreadCount

public int waitingThreadCount()

resetCurrentThread

public static CountDownLatch resetCurrentThread()
                                         throws InterruptedException

If the current thread is main thread started in response to a call to start(java.lang.String, java.lang.Runnable), this method will arrange for it to expect to be "restarted." See ThreadGroupPool.RestartableThread for more information.

Throws:

IllegalStateException - If the current thread is not a main thread.

InterruptedException