org.apache.cassandra.concurrent

Class DebuggableThreadPoolExecutor

java.lang.Object

java.util.concurrent.AbstractExecutorService

java.util.concurrent.ThreadPoolExecutor

org.apache.cassandra.concurrent.DebuggableThreadPoolExecutor

All Implemented Interfaces:

java.util.concurrent.Executor, java.util.concurrent.ExecutorService, LocalAwareExecutorService, ResizableThreadPool

Direct Known Subclasses:

JMXEnabledThreadPoolExecutor

public class DebuggableThreadPoolExecutor
extends java.util.concurrent.ThreadPoolExecutor
implements LocalAwareExecutorService

This class encorporates some Executor best practices for Cassandra. Most of the executors in the system should use or extend this. There are two main improvements over a vanilla TPE: - If a task throws an exception, the default uncaught exception handler will be invoked; if there is no such handler, the exception will be logged. - MaximumPoolSize is not supported. Here is what that means (quoting TPE javadoc): If fewer than corePoolSize threads are running, the Executor always prefers adding a new thread rather than queuing. If corePoolSize or more threads are running, the Executor always prefers queuing a request rather than adding a new thread. If a request cannot be queued, a new thread is created unless this would exceed maximumPoolSize, in which case, the task will be rejected. We don't want this last stage of creating new threads if the queue is full; it makes it needlessly difficult to reason about the system's behavior. In other words, if DebuggableTPE has allocated our maximum number of (core) threads and the queue is full, we want the enqueuer to block. But to allow the number of threads to drop if a stage is less busy, core thread timeout is enabled.

Nested Class Summary

Nested classes/interfaces inherited from class java.util.concurrent.ThreadPoolExecutor

java.util.concurrent.ThreadPoolExecutor.AbortPolicy, java.util.concurrent.ThreadPoolExecutor.CallerRunsPolicy, java.util.concurrent.ThreadPoolExecutor.DiscardOldestPolicy, java.util.concurrent.ThreadPoolExecutor.DiscardPolicy

Nested classes/interfaces inherited from interface org.apache.cassandra.concurrent.LocalAwareExecutorService

LocalAwareExecutorService.MaximumPoolSizeListener

Field Summary

Fields

Modifier and Type	Field and Description
static java.util.concurrent.RejectedExecutionHandler	blockingExecutionHandler
protected static org.slf4j.Logger	logger

Constructor Summary

Constructors

Constructor and Description
DebuggableThreadPoolExecutor(int corePoolSize, int maximumPoolSize, long keepAliveTime, java.util.concurrent.TimeUnit unit, java.util.concurrent.BlockingQueue<java.lang.Runnable> workQueue, java.util.concurrent.ThreadFactory threadFactory)
DebuggableThreadPoolExecutor(int corePoolSize, long keepAliveTime, java.util.concurrent.TimeUnit unit, java.util.concurrent.BlockingQueue<java.lang.Runnable> queue, java.util.concurrent.ThreadFactory factory)
DebuggableThreadPoolExecutor(java.lang.String threadPoolName, int priority)

Method Summary

Modifier and Type	Method and Description
protected void	afterExecute(java.lang.Runnable r, java.lang.Throwable t)
protected void	beforeExecute(java.lang.Thread t, java.lang.Runnable r)
static DebuggableThreadPoolExecutor	createCachedThreadpoolWithMaxSize(java.lang.String threadPoolName) Creates a thread pool that creates new threads as needed, but will reuse previously constructed threads when they are available.
static DebuggableThreadPoolExecutor	createWithFixedPoolSize(java.lang.String threadPoolName, int size) Returns a ThreadPoolExecutor with a fixed number of threads.
static DebuggableThreadPoolExecutor	createWithMaximumPoolSize(java.lang.String threadPoolName, int size, int keepAliveTime, java.util.concurrent.TimeUnit unit) Returns a ThreadPoolExecutor with a fixed maximum number of threads, but whose threads are terminated when idle for too long.
void	execute(java.lang.Runnable command)
void	execute(java.lang.Runnable command, ExecutorLocals locals)
static java.lang.Throwable	extractThrowable(java.lang.Runnable runnable)
int	getActiveTaskCount() Returns the approximate number of threads that are actively executing tasks.
int	getPendingTaskCount() Returns the approximate total of tasks waiting to be executed.
static void	handleOrLog(java.lang.Throwable t) Send @param t to the default uncaught exception handler, or log it if none such is set up
static void	logExceptionsAfterExecute(java.lang.Runnable r, java.lang.Throwable t) Send @param t and any exception wrapped by @param r to the default uncaught exception handler, or log them if none such is set up
void	maybeExecuteImmediately(java.lang.Runnable command)
protected static void	maybeResetTraceSessionWrapper(java.lang.Runnable r)
protected <T> java.util.concurrent.RunnableFuture<T>	newTaskFor(java.util.concurrent.Callable<T> callable)
protected <T> java.util.concurrent.RunnableFuture<T>	newTaskFor(java.lang.Runnable runnable, T result)
protected void	onFinalAccept(java.lang.Runnable task)
protected void	onFinalRejection(java.lang.Runnable task)
protected void	onInitialRejection(java.lang.Runnable task)

Methods inherited from class java.util.concurrent.ThreadPoolExecutor

allowCoreThreadTimeOut, allowsCoreThreadTimeOut, awaitTermination, finalize, getActiveCount, getCompletedTaskCount, getCorePoolSize, getKeepAliveTime, getLargestPoolSize, getMaximumPoolSize, getPoolSize, getQueue, getRejectedExecutionHandler, getTaskCount, getThreadFactory, isShutdown, isTerminated, isTerminating, prestartAllCoreThreads, prestartCoreThread, purge, remove, setCorePoolSize, setKeepAliveTime, setMaximumPoolSize, setRejectedExecutionHandler, setThreadFactory, shutdown, shutdownNow, terminated, toString

Methods inherited from class java.util.concurrent.AbstractExecutorService

invokeAll, invokeAll, invokeAny, invokeAny, submit, submit, submit

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.apache.cassandra.concurrent.LocalAwareExecutorService

getCompletedTaskCount, getMaxTasksQueued

Methods inherited from interface java.util.concurrent.ExecutorService

awaitTermination, invokeAll, invokeAll, invokeAny, invokeAny, isShutdown, isTerminated, shutdown, shutdownNow, submit, submit, submit

Methods inherited from interface org.apache.cassandra.concurrent.ResizableThreadPool

getCorePoolSize, getMaximumPoolSize, setCorePoolSize, setMaximumPoolSize

Field Detail

logger

protected static final org.slf4j.Logger logger

blockingExecutionHandler

public static final java.util.concurrent.RejectedExecutionHandler blockingExecutionHandler

Constructor Detail

DebuggableThreadPoolExecutor

public DebuggableThreadPoolExecutor(java.lang.String threadPoolName,
                                    int priority)

DebuggableThreadPoolExecutor

public DebuggableThreadPoolExecutor(int corePoolSize,
                                    long keepAliveTime,
                                    java.util.concurrent.TimeUnit unit,
                                    java.util.concurrent.BlockingQueue<java.lang.Runnable> queue,
                                    java.util.concurrent.ThreadFactory factory)

DebuggableThreadPoolExecutor

public DebuggableThreadPoolExecutor(int corePoolSize,
                                    int maximumPoolSize,
                                    long keepAliveTime,
                                    java.util.concurrent.TimeUnit unit,
                                    java.util.concurrent.BlockingQueue<java.lang.Runnable> workQueue,
                                    java.util.concurrent.ThreadFactory threadFactory)

Method Detail

createCachedThreadpoolWithMaxSize

public static DebuggableThreadPoolExecutor createCachedThreadpoolWithMaxSize(java.lang.String threadPoolName)

Creates a thread pool that creates new threads as needed, but will reuse previously constructed threads when they are available.

Parameters:

threadPoolName - the name of the threads created by this executor

Returns:

The new DebuggableThreadPoolExecutor

createWithFixedPoolSize

public static DebuggableThreadPoolExecutor createWithFixedPoolSize(java.lang.String threadPoolName,
                                                                   int size)

Returns a ThreadPoolExecutor with a fixed number of threads. When all threads are actively executing tasks, new tasks are queued. If (most) threads are expected to be idle most of the time, prefer createWithMaxSize() instead.

Parameters:

threadPoolName - the name of the threads created by this executor

size - the fixed number of threads for this executor

Returns:

the new DebuggableThreadPoolExecutor

createWithMaximumPoolSize

public static DebuggableThreadPoolExecutor createWithMaximumPoolSize(java.lang.String threadPoolName,
                                                                     int size,
                                                                     int keepAliveTime,
                                                                     java.util.concurrent.TimeUnit unit)

Returns a ThreadPoolExecutor with a fixed maximum number of threads, but whose threads are terminated when idle for too long. When all threads are actively executing tasks, new tasks are queued.

Parameters:

threadPoolName - the name of the threads created by this executor

size - the maximum number of threads for this executor

keepAliveTime - the time an idle thread is kept alive before being terminated

unit - tht time unit for keepAliveTime

Returns:

the new DebuggableThreadPoolExecutor

onInitialRejection

protected void onInitialRejection(java.lang.Runnable task)

onFinalAccept

protected void onFinalAccept(java.lang.Runnable task)

onFinalRejection

protected void onFinalRejection(java.lang.Runnable task)

execute

public void execute(java.lang.Runnable command,
                    ExecutorLocals locals)

Specified by:

execute in interface LocalAwareExecutorService

maybeExecuteImmediately

public void maybeExecuteImmediately(java.lang.Runnable command)

Specified by:

maybeExecuteImmediately in interface LocalAwareExecutorService

execute

public void execute(java.lang.Runnable command)

Specified by:

execute in interface java.util.concurrent.Executor

Overrides:

execute in class java.util.concurrent.ThreadPoolExecutor

newTaskFor

protected <T> java.util.concurrent.RunnableFuture<T> newTaskFor(java.lang.Runnable runnable,
                                                                T result)

Overrides:

newTaskFor in class java.util.concurrent.AbstractExecutorService

newTaskFor

protected <T> java.util.concurrent.RunnableFuture<T> newTaskFor(java.util.concurrent.Callable<T> callable)

Overrides:

newTaskFor in class java.util.concurrent.AbstractExecutorService

afterExecute

protected void afterExecute(java.lang.Runnable r,
                            java.lang.Throwable t)

Overrides:

afterExecute in class java.util.concurrent.ThreadPoolExecutor

maybeResetTraceSessionWrapper

protected static void maybeResetTraceSessionWrapper(java.lang.Runnable r)

beforeExecute

protected void beforeExecute(java.lang.Thread t,
                             java.lang.Runnable r)

Overrides:

beforeExecute in class java.util.concurrent.ThreadPoolExecutor

getActiveTaskCount

public int getActiveTaskCount()

Description copied from interface: LocalAwareExecutorService

Returns the approximate number of threads that are actively executing tasks.

Specified by:

getActiveTaskCount in interface LocalAwareExecutorService

Returns:

the number of threads

getPendingTaskCount

public int getPendingTaskCount()

Description copied from interface: LocalAwareExecutorService

Returns the approximate total of tasks waiting to be executed. Because the states of tasks and threads may change dynamically during computation, the returned value is only an approximation, but one that does not ever decrease across successive calls.

Specified by:

getPendingTaskCount in interface LocalAwareExecutorService

Returns:

the number of tasks

logExceptionsAfterExecute

public static void logExceptionsAfterExecute(java.lang.Runnable r,
                                             java.lang.Throwable t)

Send @param t and any exception wrapped by @param r to the default uncaught exception handler, or log them if none such is set up

handleOrLog

public static void handleOrLog(java.lang.Throwable t)

Send @param t to the default uncaught exception handler, or log it if none such is set up

extractThrowable

public static java.lang.Throwable extractThrowable(java.lang.Runnable runnable)

Returns:

any exception wrapped by @param runnable, i.e., if it is a FutureTask