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jeremybenn |
/*
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* Written by Doug Lea with assistance from members of JCP JSR-166
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* Expert Group and released to the public domain, as explained at
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* http://creativecommons.org/licenses/publicdomain
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*/
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package java.util.concurrent;
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import java.util.concurrent.locks.*;
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import java.util.*;
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/**
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* An {@link ExecutorService} that executes each submitted task using
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* one of possibly several pooled threads, normally configured
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* using {@link Executors} factory methods.
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*
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* <p>Thread pools address two different problems: they usually
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* provide improved performance when executing large numbers of
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* asynchronous tasks, due to reduced per-task invocation overhead,
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* and they provide a means of bounding and managing the resources,
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* including threads, consumed when executing a collection of tasks.
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* Each <tt>ThreadPoolExecutor</tt> also maintains some basic
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* statistics, such as the number of completed tasks.
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*
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* <p>To be useful across a wide range of contexts, this class
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* provides many adjustable parameters and extensibility
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* hooks. However, programmers are urged to use the more convenient
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* {@link Executors} factory methods {@link
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* Executors#newCachedThreadPool} (unbounded thread pool, with
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* automatic thread reclamation), {@link Executors#newFixedThreadPool}
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* (fixed size thread pool) and {@link
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* Executors#newSingleThreadExecutor} (single background thread), that
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* preconfigure settings for the most common usage
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* scenarios. Otherwise, use the following guide when manually
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* configuring and tuning this class:
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*
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* <dl>
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*
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* <dt>Core and maximum pool sizes</dt>
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*
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* <dd>A <tt>ThreadPoolExecutor</tt> will automatically adjust the
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* pool size
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* (see {@link ThreadPoolExecutor#getPoolSize})
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* according to the bounds set by corePoolSize
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* (see {@link ThreadPoolExecutor#getCorePoolSize})
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* and
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* maximumPoolSize
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* (see {@link ThreadPoolExecutor#getMaximumPoolSize}).
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* When a new task is submitted in method {@link
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* ThreadPoolExecutor#execute}, and fewer than corePoolSize threads
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* are running, a new thread is created to handle the request, even if
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* other worker threads are idle. If there are more than
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* corePoolSize but less than maximumPoolSize threads running, a new
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* thread will be created only if the queue is full. By setting
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* corePoolSize and maximumPoolSize the same, you create a fixed-size
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* thread pool. By setting maximumPoolSize to an essentially unbounded
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* value such as <tt>Integer.MAX_VALUE</tt>, you allow the pool to
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* accommodate an arbitrary number of concurrent tasks. Most typically,
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* core and maximum pool sizes are set only upon construction, but they
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* may also be changed dynamically using {@link
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* ThreadPoolExecutor#setCorePoolSize} and {@link
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* ThreadPoolExecutor#setMaximumPoolSize}. <dd>
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*
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* <dt> On-demand construction
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*
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* <dd> By default, even core threads are initially created and
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* started only when new tasks arrive, but this can be overridden
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* dynamically using method {@link
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* ThreadPoolExecutor#prestartCoreThread} or
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* {@link ThreadPoolExecutor#prestartAllCoreThreads}.
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* You probably want to prestart threads if you construct the
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* pool with a non-empty queue. </dd>
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*
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* <dt>Creating new threads</dt>
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*
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* <dd>New threads are created using a {@link
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* java.util.concurrent.ThreadFactory}. If not otherwise specified, a
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* {@link Executors#defaultThreadFactory} is used, that creates threads to all
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* be in the same {@link ThreadGroup} and with the same
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* <tt>NORM_PRIORITY</tt> priority and non-daemon status. By supplying
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* a different ThreadFactory, you can alter the thread's name, thread
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* group, priority, daemon status, etc. If a <tt>ThreadFactory</tt> fails to create
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* a thread when asked by returning null from <tt>newThread</tt>,
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* the executor will continue, but might
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* not be able to execute any tasks. </dd>
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*
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* <dt>Keep-alive times</dt>
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*
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* <dd>If the pool currently has more than corePoolSize threads,
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* excess threads will be terminated if they have been idle for more
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* than the keepAliveTime (see {@link
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* ThreadPoolExecutor#getKeepAliveTime}). This provides a means of
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* reducing resource consumption when the pool is not being actively
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* used. If the pool becomes more active later, new threads will be
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* constructed. This parameter can also be changed dynamically using
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* method {@link ThreadPoolExecutor#setKeepAliveTime}. Using a value
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* of <tt>Long.MAX_VALUE</tt> {@link TimeUnit#NANOSECONDS} effectively
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* disables idle threads from ever terminating prior to shut down. By
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* default, the keep-alive policy applies only when there are more
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* than corePoolSizeThreads. But method {@link
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* ThreadPoolExecutor#allowCoreThreadTimeOut} can be used to apply
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* this time-out policy to core threads as well, so long as
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* the keepAliveTime value is non-zero. </dd>
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*
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* <dt>Queuing</dt>
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*
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* <dd>Any {@link BlockingQueue} may be used to transfer and hold
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* submitted tasks. The use of this queue interacts with pool sizing:
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*
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* <ul>
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*
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* <li> If fewer than corePoolSize threads are running, the Executor
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* always prefers adding a new thread
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* rather than queuing.</li>
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*
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* <li> If corePoolSize or more threads are running, the Executor
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* always prefers queuing a request rather than adding a new
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* thread.</li>
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*
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* <li> If a request cannot be queued, a new thread is created unless
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* this would exceed maximumPoolSize, in which case, the task will be
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* rejected.</li>
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*
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* </ul>
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*
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* There are three general strategies for queuing:
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* <ol>
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*
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* <li> <em> Direct handoffs.</em> A good default choice for a work
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* queue is a {@link SynchronousQueue} that hands off tasks to threads
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* without otherwise holding them. Here, an attempt to queue a task
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* will fail if no threads are immediately available to run it, so a
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* new thread will be constructed. This policy avoids lockups when
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* handling sets of requests that might have internal dependencies.
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* Direct handoffs generally require unbounded maximumPoolSizes to
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* avoid rejection of new submitted tasks. This in turn admits the
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* possibility of unbounded thread growth when commands continue to
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* arrive on average faster than they can be processed. </li>
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*
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* <li><em> Unbounded queues.</em> Using an unbounded queue (for
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* example a {@link LinkedBlockingQueue} without a predefined
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* capacity) will cause new tasks to wait in the queue when all
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* corePoolSize threads are busy. Thus, no more than corePoolSize
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* threads will ever be created. (And the value of the maximumPoolSize
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* therefore doesn't have any effect.) This may be appropriate when
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* each task is completely independent of others, so tasks cannot
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* affect each others execution; for example, in a web page server.
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* While this style of queuing can be useful in smoothing out
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* transient bursts of requests, it admits the possibility of
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* unbounded work queue growth when commands continue to arrive on
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* average faster than they can be processed. </li>
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*
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* <li><em>Bounded queues.</em> A bounded queue (for example, an
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* {@link ArrayBlockingQueue}) helps prevent resource exhaustion when
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* used with finite maximumPoolSizes, but can be more difficult to
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* tune and control. Queue sizes and maximum pool sizes may be traded
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* off for each other: Using large queues and small pools minimizes
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* CPU usage, OS resources, and context-switching overhead, but can
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* lead to artificially low throughput. If tasks frequently block (for
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* example if they are I/O bound), a system may be able to schedule
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* time for more threads than you otherwise allow. Use of small queues
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* generally requires larger pool sizes, which keeps CPUs busier but
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* may encounter unacceptable scheduling overhead, which also
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* decreases throughput. </li>
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*
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* </ol>
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*
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* </dd>
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*
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* <dt>Rejected tasks</dt>
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*
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* <dd> New tasks submitted in method {@link
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* ThreadPoolExecutor#execute} will be <em>rejected</em> when the
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* Executor has been shut down, and also when the Executor uses finite
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* bounds for both maximum threads and work queue capacity, and is
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* saturated. In either case, the <tt>execute</tt> method invokes the
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* {@link RejectedExecutionHandler#rejectedExecution} method of its
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* {@link RejectedExecutionHandler}. Four predefined handler policies
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* are provided:
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*
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* <ol>
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*
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* <li> In the
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* default {@link ThreadPoolExecutor.AbortPolicy}, the handler throws a
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* runtime {@link RejectedExecutionException} upon rejection. </li>
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*
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* <li> In {@link
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* ThreadPoolExecutor.CallerRunsPolicy}, the thread that invokes
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* <tt>execute</tt> itself runs the task. This provides a simple
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* feedback control mechanism that will slow down the rate that new
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* tasks are submitted. </li>
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*
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* <li> In {@link ThreadPoolExecutor.DiscardPolicy},
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* a task that cannot be executed is simply dropped. </li>
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*
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* <li>In {@link
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* ThreadPoolExecutor.DiscardOldestPolicy}, if the executor is not
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* shut down, the task at the head of the work queue is dropped, and
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* then execution is retried (which can fail again, causing this to be
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* repeated.) </li>
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*
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* </ol>
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*
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* It is possible to define and use other kinds of {@link
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* RejectedExecutionHandler} classes. Doing so requires some care
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* especially when policies are designed to work only under particular
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* capacity or queuing policies. </dd>
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*
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* <dt>Hook methods</dt>
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*
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* <dd>This class provides <tt>protected</tt> overridable {@link
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* ThreadPoolExecutor#beforeExecute} and {@link
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* ThreadPoolExecutor#afterExecute} methods that are called before and
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* after execution of each task. These can be used to manipulate the
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* execution environment; for example, reinitializing ThreadLocals,
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* gathering statistics, or adding log entries. Additionally, method
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* {@link ThreadPoolExecutor#terminated} can be overridden to perform
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* any special processing that needs to be done once the Executor has
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* fully terminated.
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*
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* <p>If hook or callback methods throw
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* exceptions, internal worker threads may in turn fail and
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* abruptly terminate.</dd>
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*
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* <dt>Queue maintenance</dt>
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*
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* <dd> Method {@link ThreadPoolExecutor#getQueue} allows access to
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* the work queue for purposes of monitoring and debugging. Use of
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* this method for any other purpose is strongly discouraged. Two
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* supplied methods, {@link ThreadPoolExecutor#remove} and {@link
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* ThreadPoolExecutor#purge} are available to assist in storage
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* reclamation when large numbers of queued tasks become
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* cancelled.</dd>
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*
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* <dt>Finalization</dt>
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*
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* <dd> A pool that is no longer referenced in a program <em>AND</em>
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* has no remaining threads will be <tt>shutdown</tt>
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* automatically. If you would like to ensure that unreferenced pools
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* are reclaimed even if users forget to call {@link
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* ThreadPoolExecutor#shutdown}, then you must arrange that unused
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* threads eventually die, by setting appropriate keep-alive times,
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* using a lower bound of zero core threads and/or setting {@link
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* ThreadPoolExecutor#allowCoreThreadTimeOut}. </dd> </dl>
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*
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* <p> <b>Extension example</b>. Most extensions of this class
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* override one or more of the protected hook methods. For example,
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* here is a subclass that adds a simple pause/resume feature:
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*
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* <pre>
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* class PausableThreadPoolExecutor extends ThreadPoolExecutor {
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* private boolean isPaused;
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* private ReentrantLock pauseLock = new ReentrantLock();
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* private Condition unpaused = pauseLock.newCondition();
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*
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* public PausableThreadPoolExecutor(...) { super(...); }
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*
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* protected void beforeExecute(Thread t, Runnable r) {
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* super.beforeExecute(t, r);
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* pauseLock.lock();
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* try {
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* while (isPaused) unpaused.await();
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* } catch (InterruptedException ie) {
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* t.interrupt();
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* } finally {
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* pauseLock.unlock();
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* }
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* }
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*
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* public void pause() {
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* pauseLock.lock();
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* try {
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* isPaused = true;
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* } finally {
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* pauseLock.unlock();
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* }
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* }
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*
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* public void resume() {
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* pauseLock.lock();
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* try {
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* isPaused = false;
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* unpaused.signalAll();
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* } finally {
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* pauseLock.unlock();
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* }
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* }
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* }
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* </pre>
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* @since 1.5
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* @author Doug Lea
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*/
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public class ThreadPoolExecutor extends AbstractExecutorService {
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/**
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* Only used to force toArray() to produce a Runnable[].
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*/
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private static final Runnable[] EMPTY_RUNNABLE_ARRAY = new Runnable[0];
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/**
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* Permission for checking shutdown
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*/
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private static final RuntimePermission shutdownPerm =
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new RuntimePermission("modifyThread");
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/**
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* Queue used for holding tasks and handing off to worker threads.
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*/
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private final BlockingQueue<Runnable> workQueue;
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/**
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* Lock held on updates to poolSize, corePoolSize, maximumPoolSize, and
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* workers set.
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*/
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private final ReentrantLock mainLock = new ReentrantLock();
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/**
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* Wait condition to support awaitTermination
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*/
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private final Condition termination = mainLock.newCondition();
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/**
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* Set containing all worker threads in pool.
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*/
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private final HashSet<Worker> workers = new HashSet<Worker>();
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/**
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* Timeout in nanoseconds for idle threads waiting for work.
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* Threads use this timeout only when there are more than
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* corePoolSize present. Otherwise they wait forever for new work.
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*/
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private volatile long keepAliveTime;
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/**
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* If false (default) core threads stay alive even when idle.
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* If true, core threads use keepAliveTime to time out waiting for work.
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*/
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private volatile boolean allowCoreThreadTimeOut;
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/**
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|
|
* Core pool size, updated only while holding mainLock,
|
340 |
|
|
* but volatile to allow concurrent readability even
|
341 |
|
|
* during updates.
|
342 |
|
|
*/
|
343 |
|
|
private volatile int corePoolSize;
|
344 |
|
|
|
345 |
|
|
/**
|
346 |
|
|
* Maximum pool size, updated only while holding mainLock
|
347 |
|
|
* but volatile to allow concurrent readability even
|
348 |
|
|
* during updates.
|
349 |
|
|
*/
|
350 |
|
|
private volatile int maximumPoolSize;
|
351 |
|
|
|
352 |
|
|
/**
|
353 |
|
|
* Current pool size, updated only while holding mainLock
|
354 |
|
|
* but volatile to allow concurrent readability even
|
355 |
|
|
* during updates.
|
356 |
|
|
*/
|
357 |
|
|
private volatile int poolSize;
|
358 |
|
|
|
359 |
|
|
/**
|
360 |
|
|
* Lifecycle state
|
361 |
|
|
*/
|
362 |
|
|
volatile int runState;
|
363 |
|
|
|
364 |
|
|
// Special values for runState
|
365 |
|
|
/** Normal, not-shutdown mode */
|
366 |
|
|
static final int RUNNING = 0;
|
367 |
|
|
/** Controlled shutdown mode */
|
368 |
|
|
static final int SHUTDOWN = 1;
|
369 |
|
|
/** Immediate shutdown mode */
|
370 |
|
|
static final int STOP = 2;
|
371 |
|
|
/** Final state */
|
372 |
|
|
static final int TERMINATED = 3;
|
373 |
|
|
|
374 |
|
|
/**
|
375 |
|
|
* Handler called when saturated or shutdown in execute.
|
376 |
|
|
*/
|
377 |
|
|
private volatile RejectedExecutionHandler handler;
|
378 |
|
|
|
379 |
|
|
/**
|
380 |
|
|
* Factory for new threads.
|
381 |
|
|
*/
|
382 |
|
|
private volatile ThreadFactory threadFactory;
|
383 |
|
|
|
384 |
|
|
/**
|
385 |
|
|
* Tracks largest attained pool size.
|
386 |
|
|
*/
|
387 |
|
|
private int largestPoolSize;
|
388 |
|
|
|
389 |
|
|
/**
|
390 |
|
|
* Counter for completed tasks. Updated only on termination of
|
391 |
|
|
* worker threads.
|
392 |
|
|
*/
|
393 |
|
|
private long completedTaskCount;
|
394 |
|
|
|
395 |
|
|
/**
|
396 |
|
|
* The default rejected execution handler
|
397 |
|
|
*/
|
398 |
|
|
private static final RejectedExecutionHandler defaultHandler =
|
399 |
|
|
new AbortPolicy();
|
400 |
|
|
|
401 |
|
|
/**
|
402 |
|
|
* Invokes the rejected execution handler for the given command.
|
403 |
|
|
*/
|
404 |
|
|
void reject(Runnable command) {
|
405 |
|
|
handler.rejectedExecution(command, this);
|
406 |
|
|
}
|
407 |
|
|
|
408 |
|
|
/**
|
409 |
|
|
* Creates and returns a new thread running firstTask as its first
|
410 |
|
|
* task. Call only while holding mainLock.
|
411 |
|
|
* @param firstTask the task the new thread should run first (or
|
412 |
|
|
* null if none)
|
413 |
|
|
* @return the new thread, or null if threadFactory fails to create thread
|
414 |
|
|
*/
|
415 |
|
|
private Thread addThread(Runnable firstTask) {
|
416 |
|
|
if (runState == TERMINATED) // Don't create thread if terminated
|
417 |
|
|
return null;
|
418 |
|
|
Worker w = new Worker(firstTask);
|
419 |
|
|
Thread t = threadFactory.newThread(w);
|
420 |
|
|
if (t != null) {
|
421 |
|
|
w.thread = t;
|
422 |
|
|
workers.add(w);
|
423 |
|
|
int nt = ++poolSize;
|
424 |
|
|
if (nt > largestPoolSize)
|
425 |
|
|
largestPoolSize = nt;
|
426 |
|
|
}
|
427 |
|
|
return t;
|
428 |
|
|
}
|
429 |
|
|
|
430 |
|
|
/**
|
431 |
|
|
* Creates and starts a new thread running firstTask as its first
|
432 |
|
|
* task, only if fewer than corePoolSize threads are running.
|
433 |
|
|
* @param firstTask the task the new thread should run first (or
|
434 |
|
|
* null if none)
|
435 |
|
|
* @return true if successful.
|
436 |
|
|
*/
|
437 |
|
|
private boolean addIfUnderCorePoolSize(Runnable firstTask) {
|
438 |
|
|
Thread t = null;
|
439 |
|
|
final ReentrantLock mainLock = this.mainLock;
|
440 |
|
|
mainLock.lock();
|
441 |
|
|
try {
|
442 |
|
|
if (poolSize < corePoolSize)
|
443 |
|
|
t = addThread(firstTask);
|
444 |
|
|
} finally {
|
445 |
|
|
mainLock.unlock();
|
446 |
|
|
}
|
447 |
|
|
if (t == null)
|
448 |
|
|
return false;
|
449 |
|
|
t.start();
|
450 |
|
|
return true;
|
451 |
|
|
}
|
452 |
|
|
|
453 |
|
|
/**
|
454 |
|
|
* Creates and starts a new thread only if fewer than maximumPoolSize
|
455 |
|
|
* threads are running. The new thread runs as its first task the
|
456 |
|
|
* next task in queue, or if there is none, the given task.
|
457 |
|
|
* @param firstTask the task the new thread should run first (or
|
458 |
|
|
* null if none)
|
459 |
|
|
* @return 0 if a new thread cannot be created, a positive number
|
460 |
|
|
* if firstTask will be run in a new thread, or a negative number
|
461 |
|
|
* if a new thread was created but is running some other task, in
|
462 |
|
|
* which case the caller must try some other way to run firstTask
|
463 |
|
|
* (perhaps by calling this method again).
|
464 |
|
|
*/
|
465 |
|
|
private int addIfUnderMaximumPoolSize(Runnable firstTask) {
|
466 |
|
|
Thread t = null;
|
467 |
|
|
int status = 0;
|
468 |
|
|
final ReentrantLock mainLock = this.mainLock;
|
469 |
|
|
mainLock.lock();
|
470 |
|
|
try {
|
471 |
|
|
if (poolSize < maximumPoolSize) {
|
472 |
|
|
Runnable next = workQueue.poll();
|
473 |
|
|
if (next == null) {
|
474 |
|
|
next = firstTask;
|
475 |
|
|
status = 1;
|
476 |
|
|
} else
|
477 |
|
|
status = -1;
|
478 |
|
|
t = addThread(next);
|
479 |
|
|
}
|
480 |
|
|
} finally {
|
481 |
|
|
mainLock.unlock();
|
482 |
|
|
}
|
483 |
|
|
if (t == null)
|
484 |
|
|
return 0;
|
485 |
|
|
t.start();
|
486 |
|
|
return status;
|
487 |
|
|
}
|
488 |
|
|
|
489 |
|
|
|
490 |
|
|
/**
|
491 |
|
|
* Gets the next task for a worker thread to run.
|
492 |
|
|
* @return the task
|
493 |
|
|
*/
|
494 |
|
|
Runnable getTask() {
|
495 |
|
|
for (;;) {
|
496 |
|
|
try {
|
497 |
|
|
switch (runState) {
|
498 |
|
|
case RUNNING: {
|
499 |
|
|
// untimed wait if core and not allowing core timeout
|
500 |
|
|
if (poolSize <= corePoolSize && !allowCoreThreadTimeOut)
|
501 |
|
|
return workQueue.take();
|
502 |
|
|
|
503 |
|
|
long timeout = keepAliveTime;
|
504 |
|
|
if (timeout <= 0) // die immediately for 0 timeout
|
505 |
|
|
return null;
|
506 |
|
|
Runnable r = workQueue.poll(timeout, TimeUnit.NANOSECONDS);
|
507 |
|
|
if (r != null)
|
508 |
|
|
return r;
|
509 |
|
|
if (poolSize > corePoolSize || allowCoreThreadTimeOut)
|
510 |
|
|
return null; // timed out
|
511 |
|
|
// Else, after timeout, the pool shrank. Retry
|
512 |
|
|
break;
|
513 |
|
|
}
|
514 |
|
|
|
515 |
|
|
case SHUTDOWN: {
|
516 |
|
|
// Help drain queue
|
517 |
|
|
Runnable r = workQueue.poll();
|
518 |
|
|
if (r != null)
|
519 |
|
|
return r;
|
520 |
|
|
|
521 |
|
|
// Check if can terminate
|
522 |
|
|
if (workQueue.isEmpty()) {
|
523 |
|
|
interruptIdleWorkers();
|
524 |
|
|
return null;
|
525 |
|
|
}
|
526 |
|
|
|
527 |
|
|
// Else there could still be delayed tasks in queue.
|
528 |
|
|
return workQueue.take();
|
529 |
|
|
}
|
530 |
|
|
|
531 |
|
|
case STOP:
|
532 |
|
|
return null;
|
533 |
|
|
default:
|
534 |
|
|
assert false;
|
535 |
|
|
}
|
536 |
|
|
} catch (InterruptedException ie) {
|
537 |
|
|
// On interruption, re-check runstate
|
538 |
|
|
}
|
539 |
|
|
}
|
540 |
|
|
}
|
541 |
|
|
|
542 |
|
|
/**
|
543 |
|
|
* Wakes up all threads that might be waiting for tasks.
|
544 |
|
|
*/
|
545 |
|
|
void interruptIdleWorkers() {
|
546 |
|
|
final ReentrantLock mainLock = this.mainLock;
|
547 |
|
|
mainLock.lock();
|
548 |
|
|
try {
|
549 |
|
|
for (Worker w : workers)
|
550 |
|
|
w.interruptIfIdle();
|
551 |
|
|
} finally {
|
552 |
|
|
mainLock.unlock();
|
553 |
|
|
}
|
554 |
|
|
}
|
555 |
|
|
|
556 |
|
|
/**
|
557 |
|
|
* Performs bookkeeping for a terminated worker thread.
|
558 |
|
|
* @param w the worker
|
559 |
|
|
*/
|
560 |
|
|
void workerDone(Worker w) {
|
561 |
|
|
final ReentrantLock mainLock = this.mainLock;
|
562 |
|
|
mainLock.lock();
|
563 |
|
|
try {
|
564 |
|
|
completedTaskCount += w.completedTasks;
|
565 |
|
|
workers.remove(w);
|
566 |
|
|
if (--poolSize > 0)
|
567 |
|
|
return;
|
568 |
|
|
|
569 |
|
|
// Else, this is the last thread. Deal with potential shutdown.
|
570 |
|
|
|
571 |
|
|
int state = runState;
|
572 |
|
|
assert state != TERMINATED;
|
573 |
|
|
|
574 |
|
|
if (state != STOP) {
|
575 |
|
|
// If there are queued tasks but no threads, create
|
576 |
|
|
// replacement thread. We must create it initially
|
577 |
|
|
// idle to avoid orphaned tasks in case addThread
|
578 |
|
|
// fails. This also handles case of delayed tasks
|
579 |
|
|
// that will sometime later become runnable.
|
580 |
|
|
if (!workQueue.isEmpty()) {
|
581 |
|
|
Thread t = addThread(null);
|
582 |
|
|
if (t != null)
|
583 |
|
|
t.start();
|
584 |
|
|
return;
|
585 |
|
|
}
|
586 |
|
|
|
587 |
|
|
// Otherwise, we can exit without replacement
|
588 |
|
|
if (state == RUNNING)
|
589 |
|
|
return;
|
590 |
|
|
}
|
591 |
|
|
|
592 |
|
|
// Either state is STOP, or state is SHUTDOWN and there is
|
593 |
|
|
// no work to do. So we can terminate.
|
594 |
|
|
termination.signalAll();
|
595 |
|
|
runState = TERMINATED;
|
596 |
|
|
// fall through to call terminate() outside of lock.
|
597 |
|
|
} finally {
|
598 |
|
|
mainLock.unlock();
|
599 |
|
|
}
|
600 |
|
|
|
601 |
|
|
assert runState == TERMINATED;
|
602 |
|
|
terminated();
|
603 |
|
|
}
|
604 |
|
|
|
605 |
|
|
/**
|
606 |
|
|
* Worker threads
|
607 |
|
|
*/
|
608 |
|
|
private class Worker implements Runnable {
|
609 |
|
|
|
610 |
|
|
/**
|
611 |
|
|
* The runLock is acquired and released surrounding each task
|
612 |
|
|
* execution. It mainly protects against interrupts that are
|
613 |
|
|
* intended to cancel the worker thread from instead
|
614 |
|
|
* interrupting the task being run.
|
615 |
|
|
*/
|
616 |
|
|
private final ReentrantLock runLock = new ReentrantLock();
|
617 |
|
|
|
618 |
|
|
/**
|
619 |
|
|
* Initial task to run before entering run loop
|
620 |
|
|
*/
|
621 |
|
|
private Runnable firstTask;
|
622 |
|
|
|
623 |
|
|
/**
|
624 |
|
|
* Per thread completed task counter; accumulated
|
625 |
|
|
* into completedTaskCount upon termination.
|
626 |
|
|
*/
|
627 |
|
|
volatile long completedTasks;
|
628 |
|
|
|
629 |
|
|
/**
|
630 |
|
|
* Thread this worker is running in. Acts as a final field,
|
631 |
|
|
* but cannot be set until thread is created.
|
632 |
|
|
*/
|
633 |
|
|
Thread thread;
|
634 |
|
|
|
635 |
|
|
Worker(Runnable firstTask) {
|
636 |
|
|
this.firstTask = firstTask;
|
637 |
|
|
}
|
638 |
|
|
|
639 |
|
|
boolean isActive() {
|
640 |
|
|
return runLock.isLocked();
|
641 |
|
|
}
|
642 |
|
|
|
643 |
|
|
/**
|
644 |
|
|
* Interrupts thread if not running a task.
|
645 |
|
|
*/
|
646 |
|
|
void interruptIfIdle() {
|
647 |
|
|
final ReentrantLock runLock = this.runLock;
|
648 |
|
|
if (runLock.tryLock()) {
|
649 |
|
|
try {
|
650 |
|
|
thread.interrupt();
|
651 |
|
|
} finally {
|
652 |
|
|
runLock.unlock();
|
653 |
|
|
}
|
654 |
|
|
}
|
655 |
|
|
}
|
656 |
|
|
|
657 |
|
|
/**
|
658 |
|
|
* Interrupts thread even if running a task.
|
659 |
|
|
*/
|
660 |
|
|
void interruptNow() {
|
661 |
|
|
thread.interrupt();
|
662 |
|
|
}
|
663 |
|
|
|
664 |
|
|
/**
|
665 |
|
|
* Runs a single task between before/after methods.
|
666 |
|
|
*/
|
667 |
|
|
private void runTask(Runnable task) {
|
668 |
|
|
final ReentrantLock runLock = this.runLock;
|
669 |
|
|
runLock.lock();
|
670 |
|
|
try {
|
671 |
|
|
// If not shutting down then clear an outstanding interrupt.
|
672 |
|
|
if (runState != STOP &&
|
673 |
|
|
Thread.interrupted() &&
|
674 |
|
|
runState == STOP) // Re-interrupt if stopped after clearing
|
675 |
|
|
thread.interrupt();
|
676 |
|
|
boolean ran = false;
|
677 |
|
|
beforeExecute(thread, task);
|
678 |
|
|
try {
|
679 |
|
|
task.run();
|
680 |
|
|
ran = true;
|
681 |
|
|
afterExecute(task, null);
|
682 |
|
|
++completedTasks;
|
683 |
|
|
} catch (RuntimeException ex) {
|
684 |
|
|
if (!ran)
|
685 |
|
|
afterExecute(task, ex);
|
686 |
|
|
// Else the exception occurred within
|
687 |
|
|
// afterExecute itself in which case we don't
|
688 |
|
|
// want to call it again.
|
689 |
|
|
throw ex;
|
690 |
|
|
}
|
691 |
|
|
} finally {
|
692 |
|
|
runLock.unlock();
|
693 |
|
|
}
|
694 |
|
|
}
|
695 |
|
|
|
696 |
|
|
/**
|
697 |
|
|
* Main run loop
|
698 |
|
|
*/
|
699 |
|
|
public void run() {
|
700 |
|
|
try {
|
701 |
|
|
Runnable task = firstTask;
|
702 |
|
|
firstTask = null;
|
703 |
|
|
while (task != null || (task = getTask()) != null) {
|
704 |
|
|
runTask(task);
|
705 |
|
|
task = null; // unnecessary but can help GC
|
706 |
|
|
}
|
707 |
|
|
} finally {
|
708 |
|
|
workerDone(this);
|
709 |
|
|
}
|
710 |
|
|
}
|
711 |
|
|
}
|
712 |
|
|
|
713 |
|
|
// Public methods
|
714 |
|
|
|
715 |
|
|
/**
|
716 |
|
|
* Creates a new <tt>ThreadPoolExecutor</tt> with the given initial
|
717 |
|
|
* parameters and default thread factory and rejected execution handler.
|
718 |
|
|
* It may be more convenient to use one of the {@link Executors} factory
|
719 |
|
|
* methods instead of this general purpose constructor.
|
720 |
|
|
*
|
721 |
|
|
* @param corePoolSize the number of threads to keep in the
|
722 |
|
|
* pool, even if they are idle.
|
723 |
|
|
* @param maximumPoolSize the maximum number of threads to allow in the
|
724 |
|
|
* pool.
|
725 |
|
|
* @param keepAliveTime when the number of threads is greater than
|
726 |
|
|
* the core, this is the maximum time that excess idle threads
|
727 |
|
|
* will wait for new tasks before terminating.
|
728 |
|
|
* @param unit the time unit for the keepAliveTime
|
729 |
|
|
* argument.
|
730 |
|
|
* @param workQueue the queue to use for holding tasks before they
|
731 |
|
|
* are executed. This queue will hold only the <tt>Runnable</tt>
|
732 |
|
|
* tasks submitted by the <tt>execute</tt> method.
|
733 |
|
|
* @throws IllegalArgumentException if corePoolSize, or
|
734 |
|
|
* keepAliveTime less than zero, or if maximumPoolSize less than or
|
735 |
|
|
* equal to zero, or if corePoolSize greater than maximumPoolSize.
|
736 |
|
|
* @throws NullPointerException if <tt>workQueue</tt> is null
|
737 |
|
|
*/
|
738 |
|
|
public ThreadPoolExecutor(int corePoolSize,
|
739 |
|
|
int maximumPoolSize,
|
740 |
|
|
long keepAliveTime,
|
741 |
|
|
TimeUnit unit,
|
742 |
|
|
BlockingQueue<Runnable> workQueue) {
|
743 |
|
|
this(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue,
|
744 |
|
|
Executors.defaultThreadFactory(), defaultHandler);
|
745 |
|
|
}
|
746 |
|
|
|
747 |
|
|
/**
|
748 |
|
|
* Creates a new <tt>ThreadPoolExecutor</tt> with the given initial
|
749 |
|
|
* parameters and default rejected execution handler.
|
750 |
|
|
*
|
751 |
|
|
* @param corePoolSize the number of threads to keep in the
|
752 |
|
|
* pool, even if they are idle.
|
753 |
|
|
* @param maximumPoolSize the maximum number of threads to allow in the
|
754 |
|
|
* pool.
|
755 |
|
|
* @param keepAliveTime when the number of threads is greater than
|
756 |
|
|
* the core, this is the maximum time that excess idle threads
|
757 |
|
|
* will wait for new tasks before terminating.
|
758 |
|
|
* @param unit the time unit for the keepAliveTime
|
759 |
|
|
* argument.
|
760 |
|
|
* @param workQueue the queue to use for holding tasks before they
|
761 |
|
|
* are executed. This queue will hold only the <tt>Runnable</tt>
|
762 |
|
|
* tasks submitted by the <tt>execute</tt> method.
|
763 |
|
|
* @param threadFactory the factory to use when the executor
|
764 |
|
|
* creates a new thread.
|
765 |
|
|
* @throws IllegalArgumentException if corePoolSize, or
|
766 |
|
|
* keepAliveTime less than zero, or if maximumPoolSize less than or
|
767 |
|
|
* equal to zero, or if corePoolSize greater than maximumPoolSize.
|
768 |
|
|
* @throws NullPointerException if <tt>workQueue</tt>
|
769 |
|
|
* or <tt>threadFactory</tt> are null.
|
770 |
|
|
*/
|
771 |
|
|
public ThreadPoolExecutor(int corePoolSize,
|
772 |
|
|
int maximumPoolSize,
|
773 |
|
|
long keepAliveTime,
|
774 |
|
|
TimeUnit unit,
|
775 |
|
|
BlockingQueue<Runnable> workQueue,
|
776 |
|
|
ThreadFactory threadFactory) {
|
777 |
|
|
this(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue,
|
778 |
|
|
threadFactory, defaultHandler);
|
779 |
|
|
}
|
780 |
|
|
|
781 |
|
|
/**
|
782 |
|
|
* Creates a new <tt>ThreadPoolExecutor</tt> with the given initial
|
783 |
|
|
* parameters and default thread factory.
|
784 |
|
|
*
|
785 |
|
|
* @param corePoolSize the number of threads to keep in the
|
786 |
|
|
* pool, even if they are idle.
|
787 |
|
|
* @param maximumPoolSize the maximum number of threads to allow in the
|
788 |
|
|
* pool.
|
789 |
|
|
* @param keepAliveTime when the number of threads is greater than
|
790 |
|
|
* the core, this is the maximum time that excess idle threads
|
791 |
|
|
* will wait for new tasks before terminating.
|
792 |
|
|
* @param unit the time unit for the keepAliveTime
|
793 |
|
|
* argument.
|
794 |
|
|
* @param workQueue the queue to use for holding tasks before they
|
795 |
|
|
* are executed. This queue will hold only the <tt>Runnable</tt>
|
796 |
|
|
* tasks submitted by the <tt>execute</tt> method.
|
797 |
|
|
* @param handler the handler to use when execution is blocked
|
798 |
|
|
* because the thread bounds and queue capacities are reached.
|
799 |
|
|
* @throws IllegalArgumentException if corePoolSize, or
|
800 |
|
|
* keepAliveTime less than zero, or if maximumPoolSize less than or
|
801 |
|
|
* equal to zero, or if corePoolSize greater than maximumPoolSize.
|
802 |
|
|
* @throws NullPointerException if <tt>workQueue</tt>
|
803 |
|
|
* or <tt>handler</tt> are null.
|
804 |
|
|
*/
|
805 |
|
|
public ThreadPoolExecutor(int corePoolSize,
|
806 |
|
|
int maximumPoolSize,
|
807 |
|
|
long keepAliveTime,
|
808 |
|
|
TimeUnit unit,
|
809 |
|
|
BlockingQueue<Runnable> workQueue,
|
810 |
|
|
RejectedExecutionHandler handler) {
|
811 |
|
|
this(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue,
|
812 |
|
|
Executors.defaultThreadFactory(), handler);
|
813 |
|
|
}
|
814 |
|
|
|
815 |
|
|
/**
|
816 |
|
|
* Creates a new <tt>ThreadPoolExecutor</tt> with the given initial
|
817 |
|
|
* parameters.
|
818 |
|
|
*
|
819 |
|
|
* @param corePoolSize the number of threads to keep in the
|
820 |
|
|
* pool, even if they are idle.
|
821 |
|
|
* @param maximumPoolSize the maximum number of threads to allow in the
|
822 |
|
|
* pool.
|
823 |
|
|
* @param keepAliveTime when the number of threads is greater than
|
824 |
|
|
* the core, this is the maximum time that excess idle threads
|
825 |
|
|
* will wait for new tasks before terminating.
|
826 |
|
|
* @param unit the time unit for the keepAliveTime
|
827 |
|
|
* argument.
|
828 |
|
|
* @param workQueue the queue to use for holding tasks before they
|
829 |
|
|
* are executed. This queue will hold only the <tt>Runnable</tt>
|
830 |
|
|
* tasks submitted by the <tt>execute</tt> method.
|
831 |
|
|
* @param threadFactory the factory to use when the executor
|
832 |
|
|
* creates a new thread.
|
833 |
|
|
* @param handler the handler to use when execution is blocked
|
834 |
|
|
* because the thread bounds and queue capacities are reached.
|
835 |
|
|
* @throws IllegalArgumentException if corePoolSize, or
|
836 |
|
|
* keepAliveTime less than zero, or if maximumPoolSize less than or
|
837 |
|
|
* equal to zero, or if corePoolSize greater than maximumPoolSize.
|
838 |
|
|
* @throws NullPointerException if <tt>workQueue</tt>
|
839 |
|
|
* or <tt>threadFactory</tt> or <tt>handler</tt> are null.
|
840 |
|
|
*/
|
841 |
|
|
public ThreadPoolExecutor(int corePoolSize,
|
842 |
|
|
int maximumPoolSize,
|
843 |
|
|
long keepAliveTime,
|
844 |
|
|
TimeUnit unit,
|
845 |
|
|
BlockingQueue<Runnable> workQueue,
|
846 |
|
|
ThreadFactory threadFactory,
|
847 |
|
|
RejectedExecutionHandler handler) {
|
848 |
|
|
if (corePoolSize < 0 ||
|
849 |
|
|
maximumPoolSize <= 0 ||
|
850 |
|
|
maximumPoolSize < corePoolSize ||
|
851 |
|
|
keepAliveTime < 0)
|
852 |
|
|
throw new IllegalArgumentException();
|
853 |
|
|
if (workQueue == null || threadFactory == null || handler == null)
|
854 |
|
|
throw new NullPointerException();
|
855 |
|
|
this.corePoolSize = corePoolSize;
|
856 |
|
|
this.maximumPoolSize = maximumPoolSize;
|
857 |
|
|
this.workQueue = workQueue;
|
858 |
|
|
this.keepAliveTime = unit.toNanos(keepAliveTime);
|
859 |
|
|
this.threadFactory = threadFactory;
|
860 |
|
|
this.handler = handler;
|
861 |
|
|
}
|
862 |
|
|
|
863 |
|
|
|
864 |
|
|
/**
|
865 |
|
|
* Executes the given task sometime in the future. The task
|
866 |
|
|
* may execute in a new thread or in an existing pooled thread.
|
867 |
|
|
*
|
868 |
|
|
* If the task cannot be submitted for execution, either because this
|
869 |
|
|
* executor has been shutdown or because its capacity has been reached,
|
870 |
|
|
* the task is handled by the current <tt>RejectedExecutionHandler</tt>.
|
871 |
|
|
*
|
872 |
|
|
* @param command the task to execute
|
873 |
|
|
* @throws RejectedExecutionException at discretion of
|
874 |
|
|
* <tt>RejectedExecutionHandler</tt>, if task cannot be accepted
|
875 |
|
|
* for execution
|
876 |
|
|
* @throws NullPointerException if command is null
|
877 |
|
|
*/
|
878 |
|
|
public void execute(Runnable command) {
|
879 |
|
|
if (command == null)
|
880 |
|
|
throw new NullPointerException();
|
881 |
|
|
for (;;) {
|
882 |
|
|
if (runState != RUNNING) {
|
883 |
|
|
reject(command);
|
884 |
|
|
return;
|
885 |
|
|
}
|
886 |
|
|
if (poolSize < corePoolSize && addIfUnderCorePoolSize(command))
|
887 |
|
|
return;
|
888 |
|
|
if (workQueue.offer(command))
|
889 |
|
|
return;
|
890 |
|
|
int status = addIfUnderMaximumPoolSize(command);
|
891 |
|
|
if (status > 0) // created new thread
|
892 |
|
|
return;
|
893 |
|
|
if (status == 0) { // failed to create thread
|
894 |
|
|
reject(command);
|
895 |
|
|
return;
|
896 |
|
|
}
|
897 |
|
|
// Retry if created a new thread but it is busy with another task
|
898 |
|
|
}
|
899 |
|
|
}
|
900 |
|
|
|
901 |
|
|
/**
|
902 |
|
|
* Initiates an orderly shutdown in which previously submitted
|
903 |
|
|
* tasks are executed, but no new tasks will be
|
904 |
|
|
* accepted. Invocation has no additional effect if already shut
|
905 |
|
|
* down.
|
906 |
|
|
* @throws SecurityException if a security manager exists and
|
907 |
|
|
* shutting down this ExecutorService may manipulate threads that
|
908 |
|
|
* the caller is not permitted to modify because it does not hold
|
909 |
|
|
* {@link java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
|
910 |
|
|
* or the security manager's <tt>checkAccess</tt> method denies access.
|
911 |
|
|
*/
|
912 |
|
|
public void shutdown() {
|
913 |
|
|
// Fail if caller doesn't have modifyThread permission.
|
914 |
|
|
SecurityManager security = System.getSecurityManager();
|
915 |
|
|
if (security != null)
|
916 |
|
|
security.checkPermission(shutdownPerm);
|
917 |
|
|
|
918 |
|
|
boolean fullyTerminated = false;
|
919 |
|
|
final ReentrantLock mainLock = this.mainLock;
|
920 |
|
|
mainLock.lock();
|
921 |
|
|
try {
|
922 |
|
|
if (workers.size() > 0) {
|
923 |
|
|
// Check if caller can modify worker threads. This
|
924 |
|
|
// might not be true even if passed above check, if
|
925 |
|
|
// the SecurityManager treats some threads specially.
|
926 |
|
|
if (security != null) {
|
927 |
|
|
for (Worker w: workers)
|
928 |
|
|
security.checkAccess(w.thread);
|
929 |
|
|
}
|
930 |
|
|
|
931 |
|
|
int state = runState;
|
932 |
|
|
if (state == RUNNING) // don't override shutdownNow
|
933 |
|
|
runState = SHUTDOWN;
|
934 |
|
|
|
935 |
|
|
try {
|
936 |
|
|
for (Worker w: workers)
|
937 |
|
|
w.interruptIfIdle();
|
938 |
|
|
} catch (SecurityException se) {
|
939 |
|
|
// If SecurityManager allows above checks, but
|
940 |
|
|
// then unexpectedly throws exception when
|
941 |
|
|
// interrupting threads (which it ought not do),
|
942 |
|
|
// back out as cleanly as we can. Some threads may
|
943 |
|
|
// have been killed but we remain in non-shutdown
|
944 |
|
|
// state.
|
945 |
|
|
runState = state;
|
946 |
|
|
throw se;
|
947 |
|
|
}
|
948 |
|
|
}
|
949 |
|
|
else { // If no workers, trigger full termination now
|
950 |
|
|
fullyTerminated = true;
|
951 |
|
|
runState = TERMINATED;
|
952 |
|
|
termination.signalAll();
|
953 |
|
|
}
|
954 |
|
|
} finally {
|
955 |
|
|
mainLock.unlock();
|
956 |
|
|
}
|
957 |
|
|
if (fullyTerminated)
|
958 |
|
|
terminated();
|
959 |
|
|
}
|
960 |
|
|
|
961 |
|
|
|
962 |
|
|
/**
|
963 |
|
|
* Attempts to stop all actively executing tasks, halts the
|
964 |
|
|
* processing of waiting tasks, and returns a list of the tasks
|
965 |
|
|
* that were awaiting execution.
|
966 |
|
|
*
|
967 |
|
|
* <p>There are no guarantees beyond best-effort attempts to stop
|
968 |
|
|
* processing actively executing tasks. This implementation
|
969 |
|
|
* cancels tasks via {@link Thread#interrupt}, so any task that
|
970 |
|
|
* fails to respond to interrupts may never terminate.
|
971 |
|
|
*
|
972 |
|
|
* @return list of tasks that never commenced execution
|
973 |
|
|
* @throws SecurityException if a security manager exists and
|
974 |
|
|
* shutting down this ExecutorService may manipulate threads that
|
975 |
|
|
* the caller is not permitted to modify because it does not hold
|
976 |
|
|
* {@link java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
|
977 |
|
|
* or the security manager's <tt>checkAccess</tt> method denies access.
|
978 |
|
|
*/
|
979 |
|
|
public List<Runnable> shutdownNow() {
|
980 |
|
|
// Almost the same code as shutdown()
|
981 |
|
|
SecurityManager security = System.getSecurityManager();
|
982 |
|
|
if (security != null)
|
983 |
|
|
security.checkPermission(shutdownPerm);
|
984 |
|
|
|
985 |
|
|
boolean fullyTerminated = false;
|
986 |
|
|
final ReentrantLock mainLock = this.mainLock;
|
987 |
|
|
mainLock.lock();
|
988 |
|
|
try {
|
989 |
|
|
if (workers.size() > 0) {
|
990 |
|
|
if (security != null) {
|
991 |
|
|
for (Worker w: workers)
|
992 |
|
|
security.checkAccess(w.thread);
|
993 |
|
|
}
|
994 |
|
|
|
995 |
|
|
int state = runState;
|
996 |
|
|
if (state != TERMINATED)
|
997 |
|
|
runState = STOP;
|
998 |
|
|
try {
|
999 |
|
|
for (Worker w : workers)
|
1000 |
|
|
w.interruptNow();
|
1001 |
|
|
} catch (SecurityException se) {
|
1002 |
|
|
runState = state; // back out;
|
1003 |
|
|
throw se;
|
1004 |
|
|
}
|
1005 |
|
|
}
|
1006 |
|
|
else { // If no workers, trigger full termination now
|
1007 |
|
|
fullyTerminated = true;
|
1008 |
|
|
runState = TERMINATED;
|
1009 |
|
|
termination.signalAll();
|
1010 |
|
|
}
|
1011 |
|
|
} finally {
|
1012 |
|
|
mainLock.unlock();
|
1013 |
|
|
}
|
1014 |
|
|
if (fullyTerminated)
|
1015 |
|
|
terminated();
|
1016 |
|
|
return Arrays.asList(workQueue.toArray(EMPTY_RUNNABLE_ARRAY));
|
1017 |
|
|
}
|
1018 |
|
|
|
1019 |
|
|
public boolean isShutdown() {
|
1020 |
|
|
return runState != RUNNING;
|
1021 |
|
|
}
|
1022 |
|
|
|
1023 |
|
|
/**
|
1024 |
|
|
* Returns true if this executor is in the process of terminating
|
1025 |
|
|
* after <tt>shutdown</tt> or <tt>shutdownNow</tt> but has not
|
1026 |
|
|
* completely terminated. This method may be useful for
|
1027 |
|
|
* debugging. A return of <tt>true</tt> reported a sufficient
|
1028 |
|
|
* period after shutdown may indicate that submitted tasks have
|
1029 |
|
|
* ignored or suppressed interruption, causing this executor not
|
1030 |
|
|
* to properly terminate.
|
1031 |
|
|
* @return true if terminating but not yet terminated.
|
1032 |
|
|
*/
|
1033 |
|
|
public boolean isTerminating() {
|
1034 |
|
|
return runState == STOP;
|
1035 |
|
|
}
|
1036 |
|
|
|
1037 |
|
|
public boolean isTerminated() {
|
1038 |
|
|
return runState == TERMINATED;
|
1039 |
|
|
}
|
1040 |
|
|
|
1041 |
|
|
public boolean awaitTermination(long timeout, TimeUnit unit)
|
1042 |
|
|
throws InterruptedException {
|
1043 |
|
|
long nanos = unit.toNanos(timeout);
|
1044 |
|
|
final ReentrantLock mainLock = this.mainLock;
|
1045 |
|
|
mainLock.lock();
|
1046 |
|
|
try {
|
1047 |
|
|
for (;;) {
|
1048 |
|
|
if (runState == TERMINATED)
|
1049 |
|
|
return true;
|
1050 |
|
|
if (nanos <= 0)
|
1051 |
|
|
return false;
|
1052 |
|
|
nanos = termination.awaitNanos(nanos);
|
1053 |
|
|
}
|
1054 |
|
|
} finally {
|
1055 |
|
|
mainLock.unlock();
|
1056 |
|
|
}
|
1057 |
|
|
}
|
1058 |
|
|
|
1059 |
|
|
/**
|
1060 |
|
|
* Invokes <tt>shutdown</tt> when this executor is no longer
|
1061 |
|
|
* referenced.
|
1062 |
|
|
*/
|
1063 |
|
|
protected void finalize() {
|
1064 |
|
|
shutdown();
|
1065 |
|
|
}
|
1066 |
|
|
|
1067 |
|
|
/**
|
1068 |
|
|
* Sets the thread factory used to create new threads.
|
1069 |
|
|
*
|
1070 |
|
|
* @param threadFactory the new thread factory
|
1071 |
|
|
* @throws NullPointerException if threadFactory is null
|
1072 |
|
|
* @see #getThreadFactory
|
1073 |
|
|
*/
|
1074 |
|
|
public void setThreadFactory(ThreadFactory threadFactory) {
|
1075 |
|
|
if (threadFactory == null)
|
1076 |
|
|
throw new NullPointerException();
|
1077 |
|
|
this.threadFactory = threadFactory;
|
1078 |
|
|
}
|
1079 |
|
|
|
1080 |
|
|
/**
|
1081 |
|
|
* Returns the thread factory used to create new threads.
|
1082 |
|
|
*
|
1083 |
|
|
* @return the current thread factory
|
1084 |
|
|
* @see #setThreadFactory
|
1085 |
|
|
*/
|
1086 |
|
|
public ThreadFactory getThreadFactory() {
|
1087 |
|
|
return threadFactory;
|
1088 |
|
|
}
|
1089 |
|
|
|
1090 |
|
|
/**
|
1091 |
|
|
* Sets a new handler for unexecutable tasks.
|
1092 |
|
|
*
|
1093 |
|
|
* @param handler the new handler
|
1094 |
|
|
* @throws NullPointerException if handler is null
|
1095 |
|
|
* @see #getRejectedExecutionHandler
|
1096 |
|
|
*/
|
1097 |
|
|
public void setRejectedExecutionHandler(RejectedExecutionHandler handler) {
|
1098 |
|
|
if (handler == null)
|
1099 |
|
|
throw new NullPointerException();
|
1100 |
|
|
this.handler = handler;
|
1101 |
|
|
}
|
1102 |
|
|
|
1103 |
|
|
/**
|
1104 |
|
|
* Returns the current handler for unexecutable tasks.
|
1105 |
|
|
*
|
1106 |
|
|
* @return the current handler
|
1107 |
|
|
* @see #setRejectedExecutionHandler
|
1108 |
|
|
*/
|
1109 |
|
|
public RejectedExecutionHandler getRejectedExecutionHandler() {
|
1110 |
|
|
return handler;
|
1111 |
|
|
}
|
1112 |
|
|
|
1113 |
|
|
/**
|
1114 |
|
|
* Returns the task queue used by this executor. Access to the
|
1115 |
|
|
* task queue is intended primarily for debugging and monitoring.
|
1116 |
|
|
* This queue may be in active use. Retrieving the task queue
|
1117 |
|
|
* does not prevent queued tasks from executing.
|
1118 |
|
|
*
|
1119 |
|
|
* @return the task queue
|
1120 |
|
|
*/
|
1121 |
|
|
public BlockingQueue<Runnable> getQueue() {
|
1122 |
|
|
return workQueue;
|
1123 |
|
|
}
|
1124 |
|
|
|
1125 |
|
|
/**
|
1126 |
|
|
* Removes this task from the executor's internal queue if it is
|
1127 |
|
|
* present, thus causing it not to be run if it has not already
|
1128 |
|
|
* started.
|
1129 |
|
|
*
|
1130 |
|
|
* <p> This method may be useful as one part of a cancellation
|
1131 |
|
|
* scheme. It may fail to remove tasks that have been converted
|
1132 |
|
|
* into other forms before being placed on the internal queue. For
|
1133 |
|
|
* example, a task entered using <tt>submit</tt> might be
|
1134 |
|
|
* converted into a form that maintains <tt>Future</tt> status.
|
1135 |
|
|
* However, in such cases, method {@link ThreadPoolExecutor#purge}
|
1136 |
|
|
* may be used to remove those Futures that have been cancelled.
|
1137 |
|
|
*
|
1138 |
|
|
* @param task the task to remove
|
1139 |
|
|
* @return true if the task was removed
|
1140 |
|
|
*/
|
1141 |
|
|
public boolean remove(Runnable task) {
|
1142 |
|
|
return getQueue().remove(task);
|
1143 |
|
|
}
|
1144 |
|
|
|
1145 |
|
|
|
1146 |
|
|
/**
|
1147 |
|
|
* Tries to remove from the work queue all {@link Future}
|
1148 |
|
|
* tasks that have been cancelled. This method can be useful as a
|
1149 |
|
|
* storage reclamation operation, that has no other impact on
|
1150 |
|
|
* functionality. Cancelled tasks are never executed, but may
|
1151 |
|
|
* accumulate in work queues until worker threads can actively
|
1152 |
|
|
* remove them. Invoking this method instead tries to remove them now.
|
1153 |
|
|
* However, this method may fail to remove tasks in
|
1154 |
|
|
* the presence of interference by other threads.
|
1155 |
|
|
*/
|
1156 |
|
|
public void purge() {
|
1157 |
|
|
// Fail if we encounter interference during traversal
|
1158 |
|
|
try {
|
1159 |
|
|
Iterator<Runnable> it = getQueue().iterator();
|
1160 |
|
|
while (it.hasNext()) {
|
1161 |
|
|
Runnable r = it.next();
|
1162 |
|
|
if (r instanceof Future<?>) {
|
1163 |
|
|
Future<?> c = (Future<?>)r;
|
1164 |
|
|
if (c.isCancelled())
|
1165 |
|
|
it.remove();
|
1166 |
|
|
}
|
1167 |
|
|
}
|
1168 |
|
|
}
|
1169 |
|
|
catch (ConcurrentModificationException ex) {
|
1170 |
|
|
return;
|
1171 |
|
|
}
|
1172 |
|
|
}
|
1173 |
|
|
|
1174 |
|
|
/**
|
1175 |
|
|
* Sets the core number of threads. This overrides any value set
|
1176 |
|
|
* in the constructor. If the new value is smaller than the
|
1177 |
|
|
* current value, excess existing threads will be terminated when
|
1178 |
|
|
* they next become idle. If larger, new threads will, if needed,
|
1179 |
|
|
* be started to execute any queued tasks.
|
1180 |
|
|
*
|
1181 |
|
|
* @param corePoolSize the new core size
|
1182 |
|
|
* @throws IllegalArgumentException if <tt>corePoolSize</tt>
|
1183 |
|
|
* less than zero
|
1184 |
|
|
* @see #getCorePoolSize
|
1185 |
|
|
*/
|
1186 |
|
|
public void setCorePoolSize(int corePoolSize) {
|
1187 |
|
|
if (corePoolSize < 0)
|
1188 |
|
|
throw new IllegalArgumentException();
|
1189 |
|
|
final ReentrantLock mainLock = this.mainLock;
|
1190 |
|
|
mainLock.lock();
|
1191 |
|
|
try {
|
1192 |
|
|
int extra = this.corePoolSize - corePoolSize;
|
1193 |
|
|
this.corePoolSize = corePoolSize;
|
1194 |
|
|
if (extra < 0) {
|
1195 |
|
|
int n = workQueue.size();
|
1196 |
|
|
// We have to create initially-idle threads here
|
1197 |
|
|
// because we otherwise have no recourse about
|
1198 |
|
|
// what to do with a dequeued task if addThread fails.
|
1199 |
|
|
while (extra++ < 0 && n-- > 0 && poolSize < corePoolSize ) {
|
1200 |
|
|
Thread t = addThread(null);
|
1201 |
|
|
if (t != null)
|
1202 |
|
|
t.start();
|
1203 |
|
|
else
|
1204 |
|
|
break;
|
1205 |
|
|
}
|
1206 |
|
|
}
|
1207 |
|
|
else if (extra > 0 && poolSize > corePoolSize) {
|
1208 |
|
|
Iterator<Worker> it = workers.iterator();
|
1209 |
|
|
while (it.hasNext() &&
|
1210 |
|
|
extra-- > 0 &&
|
1211 |
|
|
poolSize > corePoolSize &&
|
1212 |
|
|
workQueue.remainingCapacity() == 0)
|
1213 |
|
|
it.next().interruptIfIdle();
|
1214 |
|
|
}
|
1215 |
|
|
} finally {
|
1216 |
|
|
mainLock.unlock();
|
1217 |
|
|
}
|
1218 |
|
|
}
|
1219 |
|
|
|
1220 |
|
|
/**
|
1221 |
|
|
* Returns the core number of threads.
|
1222 |
|
|
*
|
1223 |
|
|
* @return the core number of threads
|
1224 |
|
|
* @see #setCorePoolSize
|
1225 |
|
|
*/
|
1226 |
|
|
public int getCorePoolSize() {
|
1227 |
|
|
return corePoolSize;
|
1228 |
|
|
}
|
1229 |
|
|
|
1230 |
|
|
/**
|
1231 |
|
|
* Starts a core thread, causing it to idly wait for work. This
|
1232 |
|
|
* overrides the default policy of starting core threads only when
|
1233 |
|
|
* new tasks are executed. This method will return <tt>false</tt>
|
1234 |
|
|
* if all core threads have already been started.
|
1235 |
|
|
* @return true if a thread was started
|
1236 |
|
|
*/
|
1237 |
|
|
public boolean prestartCoreThread() {
|
1238 |
|
|
return addIfUnderCorePoolSize(null);
|
1239 |
|
|
}
|
1240 |
|
|
|
1241 |
|
|
/**
|
1242 |
|
|
* Starts all core threads, causing them to idly wait for work. This
|
1243 |
|
|
* overrides the default policy of starting core threads only when
|
1244 |
|
|
* new tasks are executed.
|
1245 |
|
|
* @return the number of threads started.
|
1246 |
|
|
*/
|
1247 |
|
|
public int prestartAllCoreThreads() {
|
1248 |
|
|
int n = 0;
|
1249 |
|
|
while (addIfUnderCorePoolSize(null))
|
1250 |
|
|
++n;
|
1251 |
|
|
return n;
|
1252 |
|
|
}
|
1253 |
|
|
|
1254 |
|
|
/**
|
1255 |
|
|
* Returns true if this pool allows core threads to time out and
|
1256 |
|
|
* terminate if no tasks arrive within the keepAlive time, being
|
1257 |
|
|
* replaced if needed when new tasks arrive. When true, the same
|
1258 |
|
|
* keep-alive policy applying to non-core threads applies also to
|
1259 |
|
|
* core threads. When false (the default), core threads are never
|
1260 |
|
|
* terminated due to lack of incoming tasks.
|
1261 |
|
|
* @return <tt>true</tt> if core threads are allowed to time out,
|
1262 |
|
|
* else <tt>false</tt>
|
1263 |
|
|
*
|
1264 |
|
|
* @since 1.6
|
1265 |
|
|
*/
|
1266 |
|
|
public boolean allowsCoreThreadTimeOut() {
|
1267 |
|
|
return allowCoreThreadTimeOut;
|
1268 |
|
|
}
|
1269 |
|
|
|
1270 |
|
|
/**
|
1271 |
|
|
* Sets the policy governing whether core threads may time out and
|
1272 |
|
|
* terminate if no tasks arrive within the keep-alive time, being
|
1273 |
|
|
* replaced if needed when new tasks arrive. When false, core
|
1274 |
|
|
* threads are never terminated due to lack of incoming
|
1275 |
|
|
* tasks. When true, the same keep-alive policy applying to
|
1276 |
|
|
* non-core threads applies also to core threads. To avoid
|
1277 |
|
|
* continual thread replacement, the keep-alive time must be
|
1278 |
|
|
* greater than zero when setting <tt>true</tt>. This method
|
1279 |
|
|
* should in general be called before the pool is actively used.
|
1280 |
|
|
* @param value <tt>true</tt> if should time out, else <tt>false</tt>
|
1281 |
|
|
* @throws IllegalArgumentException if value is <tt>true</tt>
|
1282 |
|
|
* and the current keep-alive time is not greater than zero.
|
1283 |
|
|
*
|
1284 |
|
|
* @since 1.6
|
1285 |
|
|
*/
|
1286 |
|
|
public void allowCoreThreadTimeOut(boolean value) {
|
1287 |
|
|
if (value && keepAliveTime <= 0)
|
1288 |
|
|
throw new IllegalArgumentException("Core threads must have nonzero keep alive times");
|
1289 |
|
|
|
1290 |
|
|
allowCoreThreadTimeOut = value;
|
1291 |
|
|
}
|
1292 |
|
|
|
1293 |
|
|
/**
|
1294 |
|
|
* Sets the maximum allowed number of threads. This overrides any
|
1295 |
|
|
* value set in the constructor. If the new value is smaller than
|
1296 |
|
|
* the current value, excess existing threads will be
|
1297 |
|
|
* terminated when they next become idle.
|
1298 |
|
|
*
|
1299 |
|
|
* @param maximumPoolSize the new maximum
|
1300 |
|
|
* @throws IllegalArgumentException if the new maximum is
|
1301 |
|
|
* less than or equal to zero, or
|
1302 |
|
|
* less than the {@linkplain #getCorePoolSize core pool size}
|
1303 |
|
|
* @see #getMaximumPoolSize
|
1304 |
|
|
*/
|
1305 |
|
|
public void setMaximumPoolSize(int maximumPoolSize) {
|
1306 |
|
|
if (maximumPoolSize <= 0 || maximumPoolSize < corePoolSize)
|
1307 |
|
|
throw new IllegalArgumentException();
|
1308 |
|
|
final ReentrantLock mainLock = this.mainLock;
|
1309 |
|
|
mainLock.lock();
|
1310 |
|
|
try {
|
1311 |
|
|
int extra = this.maximumPoolSize - maximumPoolSize;
|
1312 |
|
|
this.maximumPoolSize = maximumPoolSize;
|
1313 |
|
|
if (extra > 0 && poolSize > maximumPoolSize) {
|
1314 |
|
|
Iterator<Worker> it = workers.iterator();
|
1315 |
|
|
while (it.hasNext() &&
|
1316 |
|
|
extra > 0 &&
|
1317 |
|
|
poolSize > maximumPoolSize) {
|
1318 |
|
|
it.next().interruptIfIdle();
|
1319 |
|
|
--extra;
|
1320 |
|
|
}
|
1321 |
|
|
}
|
1322 |
|
|
} finally {
|
1323 |
|
|
mainLock.unlock();
|
1324 |
|
|
}
|
1325 |
|
|
}
|
1326 |
|
|
|
1327 |
|
|
/**
|
1328 |
|
|
* Returns the maximum allowed number of threads.
|
1329 |
|
|
*
|
1330 |
|
|
* @return the maximum allowed number of threads
|
1331 |
|
|
* @see #setMaximumPoolSize
|
1332 |
|
|
*/
|
1333 |
|
|
public int getMaximumPoolSize() {
|
1334 |
|
|
return maximumPoolSize;
|
1335 |
|
|
}
|
1336 |
|
|
|
1337 |
|
|
/**
|
1338 |
|
|
* Sets the time limit for which threads may remain idle before
|
1339 |
|
|
* being terminated. If there are more than the core number of
|
1340 |
|
|
* threads currently in the pool, after waiting this amount of
|
1341 |
|
|
* time without processing a task, excess threads will be
|
1342 |
|
|
* terminated. This overrides any value set in the constructor.
|
1343 |
|
|
* @param time the time to wait. A time value of zero will cause
|
1344 |
|
|
* excess threads to terminate immediately after executing tasks.
|
1345 |
|
|
* @param unit the time unit of the time argument
|
1346 |
|
|
* @throws IllegalArgumentException if time less than zero or
|
1347 |
|
|
* if time is zero and allowsCoreThreadTimeOut
|
1348 |
|
|
* @see #getKeepAliveTime
|
1349 |
|
|
*/
|
1350 |
|
|
public void setKeepAliveTime(long time, TimeUnit unit) {
|
1351 |
|
|
if (time < 0)
|
1352 |
|
|
throw new IllegalArgumentException();
|
1353 |
|
|
if (time == 0 && allowsCoreThreadTimeOut())
|
1354 |
|
|
throw new IllegalArgumentException("Core threads must have nonzero keep alive times");
|
1355 |
|
|
this.keepAliveTime = unit.toNanos(time);
|
1356 |
|
|
}
|
1357 |
|
|
|
1358 |
|
|
/**
|
1359 |
|
|
* Returns the thread keep-alive time, which is the amount of time
|
1360 |
|
|
* which threads in excess of the core pool size may remain
|
1361 |
|
|
* idle before being terminated.
|
1362 |
|
|
*
|
1363 |
|
|
* @param unit the desired time unit of the result
|
1364 |
|
|
* @return the time limit
|
1365 |
|
|
* @see #setKeepAliveTime
|
1366 |
|
|
*/
|
1367 |
|
|
public long getKeepAliveTime(TimeUnit unit) {
|
1368 |
|
|
return unit.convert(keepAliveTime, TimeUnit.NANOSECONDS);
|
1369 |
|
|
}
|
1370 |
|
|
|
1371 |
|
|
/* Statistics */
|
1372 |
|
|
|
1373 |
|
|
/**
|
1374 |
|
|
* Returns the current number of threads in the pool.
|
1375 |
|
|
*
|
1376 |
|
|
* @return the number of threads
|
1377 |
|
|
*/
|
1378 |
|
|
public int getPoolSize() {
|
1379 |
|
|
return poolSize;
|
1380 |
|
|
}
|
1381 |
|
|
|
1382 |
|
|
/**
|
1383 |
|
|
* Returns the approximate number of threads that are actively
|
1384 |
|
|
* executing tasks.
|
1385 |
|
|
*
|
1386 |
|
|
* @return the number of threads
|
1387 |
|
|
*/
|
1388 |
|
|
public int getActiveCount() {
|
1389 |
|
|
final ReentrantLock mainLock = this.mainLock;
|
1390 |
|
|
mainLock.lock();
|
1391 |
|
|
try {
|
1392 |
|
|
int n = 0;
|
1393 |
|
|
for (Worker w : workers) {
|
1394 |
|
|
if (w.isActive())
|
1395 |
|
|
++n;
|
1396 |
|
|
}
|
1397 |
|
|
return n;
|
1398 |
|
|
} finally {
|
1399 |
|
|
mainLock.unlock();
|
1400 |
|
|
}
|
1401 |
|
|
}
|
1402 |
|
|
|
1403 |
|
|
/**
|
1404 |
|
|
* Returns the largest number of threads that have ever
|
1405 |
|
|
* simultaneously been in the pool.
|
1406 |
|
|
*
|
1407 |
|
|
* @return the number of threads
|
1408 |
|
|
*/
|
1409 |
|
|
public int getLargestPoolSize() {
|
1410 |
|
|
final ReentrantLock mainLock = this.mainLock;
|
1411 |
|
|
mainLock.lock();
|
1412 |
|
|
try {
|
1413 |
|
|
return largestPoolSize;
|
1414 |
|
|
} finally {
|
1415 |
|
|
mainLock.unlock();
|
1416 |
|
|
}
|
1417 |
|
|
}
|
1418 |
|
|
|
1419 |
|
|
/**
|
1420 |
|
|
* Returns the approximate total number of tasks that have been
|
1421 |
|
|
* scheduled for execution. Because the states of tasks and
|
1422 |
|
|
* threads may change dynamically during computation, the returned
|
1423 |
|
|
* value is only an approximation, but one that does not ever
|
1424 |
|
|
* decrease across successive calls.
|
1425 |
|
|
*
|
1426 |
|
|
* @return the number of tasks
|
1427 |
|
|
*/
|
1428 |
|
|
public long getTaskCount() {
|
1429 |
|
|
final ReentrantLock mainLock = this.mainLock;
|
1430 |
|
|
mainLock.lock();
|
1431 |
|
|
try {
|
1432 |
|
|
long n = completedTaskCount;
|
1433 |
|
|
for (Worker w : workers) {
|
1434 |
|
|
n += w.completedTasks;
|
1435 |
|
|
if (w.isActive())
|
1436 |
|
|
++n;
|
1437 |
|
|
}
|
1438 |
|
|
return n + workQueue.size();
|
1439 |
|
|
} finally {
|
1440 |
|
|
mainLock.unlock();
|
1441 |
|
|
}
|
1442 |
|
|
}
|
1443 |
|
|
|
1444 |
|
|
/**
|
1445 |
|
|
* Returns the approximate total number of tasks that have
|
1446 |
|
|
* completed execution. Because the states of tasks and threads
|
1447 |
|
|
* may change dynamically during computation, the returned value
|
1448 |
|
|
* is only an approximation, but one that does not ever decrease
|
1449 |
|
|
* across successive calls.
|
1450 |
|
|
*
|
1451 |
|
|
* @return the number of tasks
|
1452 |
|
|
*/
|
1453 |
|
|
public long getCompletedTaskCount() {
|
1454 |
|
|
final ReentrantLock mainLock = this.mainLock;
|
1455 |
|
|
mainLock.lock();
|
1456 |
|
|
try {
|
1457 |
|
|
long n = completedTaskCount;
|
1458 |
|
|
for (Worker w : workers)
|
1459 |
|
|
n += w.completedTasks;
|
1460 |
|
|
return n;
|
1461 |
|
|
} finally {
|
1462 |
|
|
mainLock.unlock();
|
1463 |
|
|
}
|
1464 |
|
|
}
|
1465 |
|
|
|
1466 |
|
|
/**
|
1467 |
|
|
* Method invoked prior to executing the given Runnable in the
|
1468 |
|
|
* given thread. This method is invoked by thread <tt>t</tt> that
|
1469 |
|
|
* will execute task <tt>r</tt>, and may be used to re-initialize
|
1470 |
|
|
* ThreadLocals, or to perform logging.
|
1471 |
|
|
*
|
1472 |
|
|
* <p>This implementation does nothing, but may be customized in
|
1473 |
|
|
* subclasses. Note: To properly nest multiple overridings, subclasses
|
1474 |
|
|
* should generally invoke <tt>super.beforeExecute</tt> at the end of
|
1475 |
|
|
* this method.
|
1476 |
|
|
*
|
1477 |
|
|
* @param t the thread that will run task r.
|
1478 |
|
|
* @param r the task that will be executed.
|
1479 |
|
|
*/
|
1480 |
|
|
protected void beforeExecute(Thread t, Runnable r) { }
|
1481 |
|
|
|
1482 |
|
|
/**
|
1483 |
|
|
* Method invoked upon completion of execution of the given Runnable.
|
1484 |
|
|
* This method is invoked by the thread that executed the task. If
|
1485 |
|
|
* non-null, the Throwable is the uncaught <tt>RuntimeException</tt>
|
1486 |
|
|
* or <tt>Error</tt> that caused execution to terminate abruptly.
|
1487 |
|
|
*
|
1488 |
|
|
* <p><b>Note:</b> When actions are enclosed in tasks (such as
|
1489 |
|
|
* {@link FutureTask}) either explicitly or via methods such as
|
1490 |
|
|
* <tt>submit</tt>, these task objects catch and maintain
|
1491 |
|
|
* computational exceptions, and so they do not cause abrupt
|
1492 |
|
|
* termination, and the internal exceptions are <em>not</em>
|
1493 |
|
|
* passed to this method.
|
1494 |
|
|
*
|
1495 |
|
|
* <p>This implementation does nothing, but may be customized in
|
1496 |
|
|
* subclasses. Note: To properly nest multiple overridings, subclasses
|
1497 |
|
|
* should generally invoke <tt>super.afterExecute</tt> at the
|
1498 |
|
|
* beginning of this method.
|
1499 |
|
|
*
|
1500 |
|
|
* @param r the runnable that has completed.
|
1501 |
|
|
* @param t the exception that caused termination, or null if
|
1502 |
|
|
* execution completed normally.
|
1503 |
|
|
*/
|
1504 |
|
|
protected void afterExecute(Runnable r, Throwable t) { }
|
1505 |
|
|
|
1506 |
|
|
/**
|
1507 |
|
|
* Method invoked when the Executor has terminated. Default
|
1508 |
|
|
* implementation does nothing. Note: To properly nest multiple
|
1509 |
|
|
* overridings, subclasses should generally invoke
|
1510 |
|
|
* <tt>super.terminated</tt> within this method.
|
1511 |
|
|
*/
|
1512 |
|
|
protected void terminated() { }
|
1513 |
|
|
|
1514 |
|
|
/**
|
1515 |
|
|
* A handler for rejected tasks that runs the rejected task
|
1516 |
|
|
* directly in the calling thread of the <tt>execute</tt> method,
|
1517 |
|
|
* unless the executor has been shut down, in which case the task
|
1518 |
|
|
* is discarded.
|
1519 |
|
|
*/
|
1520 |
|
|
public static class CallerRunsPolicy implements RejectedExecutionHandler {
|
1521 |
|
|
/**
|
1522 |
|
|
* Creates a <tt>CallerRunsPolicy</tt>.
|
1523 |
|
|
*/
|
1524 |
|
|
public CallerRunsPolicy() { }
|
1525 |
|
|
|
1526 |
|
|
/**
|
1527 |
|
|
* Executes task r in the caller's thread, unless the executor
|
1528 |
|
|
* has been shut down, in which case the task is discarded.
|
1529 |
|
|
* @param r the runnable task requested to be executed
|
1530 |
|
|
* @param e the executor attempting to execute this task
|
1531 |
|
|
*/
|
1532 |
|
|
public void rejectedExecution(Runnable r, ThreadPoolExecutor e) {
|
1533 |
|
|
if (!e.isShutdown()) {
|
1534 |
|
|
r.run();
|
1535 |
|
|
}
|
1536 |
|
|
}
|
1537 |
|
|
}
|
1538 |
|
|
|
1539 |
|
|
/**
|
1540 |
|
|
* A handler for rejected tasks that throws a
|
1541 |
|
|
* <tt>RejectedExecutionException</tt>.
|
1542 |
|
|
*/
|
1543 |
|
|
public static class AbortPolicy implements RejectedExecutionHandler {
|
1544 |
|
|
/**
|
1545 |
|
|
* Creates an <tt>AbortPolicy</tt>.
|
1546 |
|
|
*/
|
1547 |
|
|
public AbortPolicy() { }
|
1548 |
|
|
|
1549 |
|
|
/**
|
1550 |
|
|
* Always throws RejectedExecutionException.
|
1551 |
|
|
* @param r the runnable task requested to be executed
|
1552 |
|
|
* @param e the executor attempting to execute this task
|
1553 |
|
|
* @throws RejectedExecutionException always.
|
1554 |
|
|
*/
|
1555 |
|
|
public void rejectedExecution(Runnable r, ThreadPoolExecutor e) {
|
1556 |
|
|
throw new RejectedExecutionException();
|
1557 |
|
|
}
|
1558 |
|
|
}
|
1559 |
|
|
|
1560 |
|
|
/**
|
1561 |
|
|
* A handler for rejected tasks that silently discards the
|
1562 |
|
|
* rejected task.
|
1563 |
|
|
*/
|
1564 |
|
|
public static class DiscardPolicy implements RejectedExecutionHandler {
|
1565 |
|
|
/**
|
1566 |
|
|
* Creates a <tt>DiscardPolicy</tt>.
|
1567 |
|
|
*/
|
1568 |
|
|
public DiscardPolicy() { }
|
1569 |
|
|
|
1570 |
|
|
/**
|
1571 |
|
|
* Does nothing, which has the effect of discarding task r.
|
1572 |
|
|
* @param r the runnable task requested to be executed
|
1573 |
|
|
* @param e the executor attempting to execute this task
|
1574 |
|
|
*/
|
1575 |
|
|
public void rejectedExecution(Runnable r, ThreadPoolExecutor e) {
|
1576 |
|
|
}
|
1577 |
|
|
}
|
1578 |
|
|
|
1579 |
|
|
/**
|
1580 |
|
|
* A handler for rejected tasks that discards the oldest unhandled
|
1581 |
|
|
* request and then retries <tt>execute</tt>, unless the executor
|
1582 |
|
|
* is shut down, in which case the task is discarded.
|
1583 |
|
|
*/
|
1584 |
|
|
public static class DiscardOldestPolicy implements RejectedExecutionHandler {
|
1585 |
|
|
/**
|
1586 |
|
|
* Creates a <tt>DiscardOldestPolicy</tt> for the given executor.
|
1587 |
|
|
*/
|
1588 |
|
|
public DiscardOldestPolicy() { }
|
1589 |
|
|
|
1590 |
|
|
/**
|
1591 |
|
|
* Obtains and ignores the next task that the executor
|
1592 |
|
|
* would otherwise execute, if one is immediately available,
|
1593 |
|
|
* and then retries execution of task r, unless the executor
|
1594 |
|
|
* is shut down, in which case task r is instead discarded.
|
1595 |
|
|
* @param r the runnable task requested to be executed
|
1596 |
|
|
* @param e the executor attempting to execute this task
|
1597 |
|
|
*/
|
1598 |
|
|
public void rejectedExecution(Runnable r, ThreadPoolExecutor e) {
|
1599 |
|
|
if (!e.isShutdown()) {
|
1600 |
|
|
e.getQueue().poll();
|
1601 |
|
|
e.execute(r);
|
1602 |
|
|
}
|
1603 |
|
|
}
|
1604 |
|
|
}
|
1605 |
|
|
}
|