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/* |
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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. Use, modify, and |
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* redistribute this code in any way without acknowledgement. |
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1.1 |
*/ |
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package java.util.concurrent; |
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1.9 |
import java.util.concurrent.locks.*; |
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import java.util.*; |
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1.1 |
|
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/** |
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1.2 |
* An {@link ExecutorService} that executes each submitted task on one |
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1.1 |
* of several pooled threads. |
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* |
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* <p>Thread pools address two different problems at the same time: |
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* they usually provide improved performance when executing large |
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* numbers of asynchronous tasks, due to reduced per-task invocation |
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* overhead, and they provide a means of bounding and managing the |
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* resources, including threads, consumed in executing a collection of |
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* tasks. |
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* |
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* <p>This class is very configurable and can be configured to create |
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* a new thread for each task, or even to execute tasks sequentially |
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* in a single thread, in addition to its most common configuration, |
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* which reuses a pool of threads. |
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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 hooks. |
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* However, programmers are urged to use the more convenient factory |
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* methods <tt>newCachedThreadPool</tt> (unbounded thread pool, with |
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* automatic thread reclamation), <tt>newFixedThreadPool</tt> (fixed |
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* size thread pool), <tt>newSingleThreadPoolExecutor</tt> (single |
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* background thread for execution of tasks), and |
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* <tt>newThreadPerTaskExeceutor</tt> (execute each task in a new |
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* thread), that preconfigure settings for the most common usage |
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* scenarios. |
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* |
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* <p>This class also maintain some basic statistics, such as the |
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* number of completed tasks, that may be useful for monitoring and |
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* tuning executors. |
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* |
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* <h3>Tuning guide</h3> |
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* <dl> |
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* |
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* <dt>Core and maximum pool size</dt> |
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* |
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* <dd>A ThreadPoolExecutor will automatically adjust the pool size |
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* according to the bounds set by corePoolSize and maximumPoolSize. |
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* When a new task is submitted, 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 the |
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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.</dd> |
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* |
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* <dt>Keep-alive</dt> |
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* |
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* <dd>The keepAliveTime determines what happens to idle threads. If |
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* the pool currently has more than the core number of threads, excess |
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* threads will be terminated if they have been idle for more than the |
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* keepAliveTime.</dd> |
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* |
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* <dt>Queueing</dt> |
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* |
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* <dd>You are free to specify the queuing mechanism used to handle |
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* submitted tasks. A good default is to use queueless synchronous |
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* channels to to hand off work to threads. This is a safe, |
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* conservative policy that avoids lockups when handling sets of |
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* requests that might have internal dependencies. Using an unbounded |
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* queue (for example a LinkedBlockingQueue) which will cause new |
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* tasks to be queued in cases where all corePoolSize threads are |
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* busy, so no more that corePoolSize threads will be craated. This |
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* may be appropriate when each task is completely independent of |
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* others, so tasks cannot affect each others execution. For example, |
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* in an http server. When given a choice, this pool always prefers |
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* adding a new thread rather than queueing if there are currently |
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* fewer than the current getCorePoolSize threads running, but |
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* otherwise always prefers queuing a request rather than adding a new |
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* thread. |
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* |
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* <p>While queuing can be useful in smoothing out transient bursts of |
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* requests, especially in socket-based services, it is not very well |
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* behaved when commands continue to arrive on average faster than |
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* they can be processed. |
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* |
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* Queue sizes and maximum pool sizes can often be traded off for each |
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* other. Using large queues and small pools minimizes CPU usage, OS |
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* resources, and context-switching overhead, but can lead to |
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* artifically low throughput. If tasks frequently block (for example |
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* if they are I/O bound), a JVM and underlying OS may be able to |
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* schedule time for more threads than you otherwise allow. Use of |
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* small queues or queueless handoffs generally requires larger pool |
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* sizes, which keeps CPUs busier but may encounter unacceptable |
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* scheduling overhead, which also decreases throughput. |
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* </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 ThreadFactory. By default, |
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* threads are created simply with the new Thread(Runnable) |
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* constructor, but by supplying a different ThreadFactory, you can |
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* alter the thread's name, thread group, priority, daemon status, |
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* etc. </dd> |
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* |
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* <dt>Before and after intercepts</dt> |
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* |
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* <dd>This class has overridable methods that which are called before |
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* and after execution of each task. These can be used to manipulate |
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* the execution environment (for example, reinitializing |
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* ThreadLocals), gather statistics, or perform logging. </dd> |
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* |
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* <dt>Blocked execution</dt> |
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* |
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* <dd>There are a number of factors which can bound the number of |
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* tasks which can execute at once, including the maximum pool size |
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* and the queuing mechanism used. If the executor determines that a |
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* task cannot be executed because it has been refused by the queue |
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* and no threads are available, or because the executor has been shut |
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* down, the RejectedExecutionHandler's rejectedExecution method is |
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* invoked. </dd> |
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* |
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* <dt>Termination</dt> |
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* |
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* <dd>ThreadPoolExecutor supports two shutdown options, immediate and |
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* graceful. In an immediate shutdown, any threads currently |
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* executing are interrupted, and any tasks not yet begun are returned |
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* from the shutdownNow call. In a graceful shutdown, all queued |
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* tasks are allowed to run, but new tasks may not be submitted. |
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* </dd> |
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* |
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* </dl> |
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* |
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* @since 1.5 |
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1.2 |
* @see RejectedExecutionHandler |
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1.1 |
* @see Executors |
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* @see ThreadFactory |
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* |
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* @spec JSR-166 |
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1.15 |
* @revised $Date: 2003/08/08 20:05:07 $ |
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* @editor $Author: tim $ |
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1.8 |
* @author Doug Lea |
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1.1 |
*/ |
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1.2 |
public class ThreadPoolExecutor implements ExecutorService { |
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/** |
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* Queue used for holding tasks and handing off to worker threads. |
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1.10 |
*/ |
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1.2 |
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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1.10 |
*/ |
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1.2 |
private final ReentrantLock mainLock = new ReentrantLock(); |
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/** |
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* Wait condition to support awaitTermination |
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1.10 |
*/ |
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1.2 |
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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1.10 |
*/ |
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1.2 |
private final Set<Worker> workers = new HashSet<Worker>(); |
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/** |
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* Timeout in nanosecods 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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1.10 |
*/ |
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1.2 |
private volatile long keepAliveTime; |
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/** |
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* Core pool size, updated only while holding mainLock, |
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* but volatile to allow concurrent readability even |
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* during updates. |
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1.10 |
*/ |
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1.2 |
private volatile int corePoolSize; |
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/** |
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* Maximum pool size, updated only while holding mainLock |
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* but volatile to allow concurrent readability even |
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* during updates. |
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1.10 |
*/ |
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1.2 |
private volatile int maximumPoolSize; |
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/** |
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* Current pool size, updated only while holding mainLock |
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* but volatile to allow concurrent readability even |
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* during updates. |
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1.10 |
*/ |
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1.2 |
private volatile int poolSize; |
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/** |
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* Shutdown status, becomes (and remains) nonzero when shutdown called. |
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1.10 |
*/ |
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1.2 |
private volatile int shutdownStatus; |
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// Special values for status |
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1.8 |
/** Normal, not-shutdown mode */ |
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1.2 |
private static final int NOT_SHUTDOWN = 0; |
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1.8 |
/** Controlled shutdown mode */ |
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1.2 |
private static final int SHUTDOWN_WHEN_IDLE = 1; |
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1.8 |
/*8 Immediate shutdown mode */ |
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1.10 |
private static final int SHUTDOWN_NOW = 2; |
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1.2 |
|
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/** |
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* Latch that becomes true when all threads terminate after shutdown. |
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1.10 |
*/ |
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1.2 |
private volatile boolean isTerminated; |
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/** |
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* Handler called when saturated or shutdown in execute. |
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1.10 |
*/ |
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1.2 |
private volatile RejectedExecutionHandler handler = defaultHandler; |
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/** |
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* Factory for new threads. |
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1.10 |
*/ |
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1.2 |
private volatile ThreadFactory threadFactory = defaultThreadFactory; |
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/** |
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* Tracks largest attained pool size. |
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1.10 |
*/ |
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1.2 |
private int largestPoolSize; |
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/** |
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* Counter for completed tasks. Updated only on termination of |
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* worker threads. |
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1.10 |
*/ |
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1.2 |
private long completedTaskCount; |
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1.8 |
/** |
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1.10 |
* The default thread facotry |
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1.8 |
*/ |
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tim |
1.10 |
private static final ThreadFactory defaultThreadFactory = |
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1.2 |
new ThreadFactory() { |
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public Thread newThread(Runnable r) { |
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return new Thread(r); |
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} |
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}; |
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dl |
1.8 |
/** |
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* The default rejectect execution handler |
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*/ |
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1.10 |
private static final RejectedExecutionHandler defaultHandler = |
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1.2 |
new AbortPolicy(); |
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/** |
250 |
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1.13 |
* Invoke the rejected execution handler for the give command. |
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*/ |
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void reject(Runnable command) { |
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handler.rejectedExecution(command, this); |
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} |
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/** |
258 |
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1.2 |
* Create and return a new thread running firstTask as its first |
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* task. Call only while holding mainLock |
260 |
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1.8 |
* @param firstTask the task the new thread should run first (or |
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* null if none) |
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* @return the new thread |
263 |
dl |
1.2 |
*/ |
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private Thread addThread(Runnable firstTask) { |
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Worker w = new Worker(firstTask); |
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Thread t = threadFactory.newThread(w); |
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w.thread = t; |
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workers.add(w); |
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int nt = ++poolSize; |
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if (nt > largestPoolSize) |
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largestPoolSize = nt; |
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return t; |
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} |
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dl |
1.15 |
// addIfUnderCorePoolSize is non-private; accessible to ScheduledExecutor |
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277 |
dl |
1.2 |
/** |
278 |
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* Create and start a new thread running firstTask as its first |
279 |
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* task, only if less than corePoolSize threads are running. |
280 |
dl |
1.8 |
* @param firstTask the task the new thread should run first (or |
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* null if none) |
282 |
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1.2 |
* @return true if successful. |
283 |
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*/ |
284 |
dl |
1.13 |
boolean addIfUnderCorePoolSize(Runnable firstTask) { |
285 |
dl |
1.2 |
Thread t = null; |
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mainLock.lock(); |
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try { |
288 |
tim |
1.10 |
if (poolSize < corePoolSize) |
289 |
dl |
1.8 |
t = addThread(firstTask); |
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tim |
1.14 |
} finally { |
291 |
dl |
1.2 |
mainLock.unlock(); |
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} |
293 |
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if (t == null) |
294 |
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return false; |
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t.start(); |
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return true; |
297 |
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} |
298 |
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299 |
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/** |
300 |
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* Create and start a new thread only if less than maximumPoolSize |
301 |
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* threads are running. The new thread runs as its first task the |
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* next task in queue, or if there is none, the given task. |
303 |
dl |
1.8 |
* @param firstTask the task the new thread should run first (or |
304 |
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* null if none) |
305 |
dl |
1.2 |
* @return null on failure, else the first task to be run by new thread. |
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*/ |
307 |
dl |
1.8 |
private Runnable addIfUnderMaximumPoolSize(Runnable firstTask) { |
308 |
dl |
1.2 |
Thread t = null; |
309 |
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Runnable next = null; |
310 |
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mainLock.lock(); |
311 |
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try { |
312 |
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if (poolSize < maximumPoolSize) { |
313 |
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next = workQueue.poll(); |
314 |
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if (next == null) |
315 |
dl |
1.8 |
next = firstTask; |
316 |
dl |
1.2 |
t = addThread(next); |
317 |
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} |
318 |
tim |
1.14 |
} finally { |
319 |
dl |
1.2 |
mainLock.unlock(); |
320 |
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} |
321 |
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if (t == null) |
322 |
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return null; |
323 |
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t.start(); |
324 |
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return next; |
325 |
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} |
326 |
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327 |
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328 |
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/** |
329 |
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* Get the next task for a worker thread to run. |
330 |
dl |
1.8 |
* @return the task |
331 |
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* @throws InterruptedException if interrupted while waiting for task |
332 |
dl |
1.2 |
*/ |
333 |
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private Runnable getTask() throws InterruptedException { |
334 |
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for (;;) { |
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int stat = shutdownStatus; |
336 |
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if (stat == SHUTDOWN_NOW) |
337 |
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return null; |
338 |
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if (stat == SHUTDOWN_WHEN_IDLE) // help drain queue before dying |
339 |
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return workQueue.poll(); |
340 |
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if (poolSize <= corePoolSize) // untimed wait if core |
341 |
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return workQueue.take(); |
342 |
dl |
1.12 |
long timeout = keepAliveTime; |
343 |
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if (timeout <= 0) // must die immediately for 0 timeout |
344 |
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return null; |
345 |
dl |
1.2 |
Runnable task = workQueue.poll(timeout, TimeUnit.NANOSECONDS); |
346 |
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if (task != null) |
347 |
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return task; |
348 |
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if (poolSize > corePoolSize) // timed out |
349 |
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return null; |
350 |
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// else, after timeout, pool shrank so shouldn't die, so retry |
351 |
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} |
352 |
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} |
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354 |
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/** |
355 |
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* Perform bookkeeping for a terminated worker thread. |
356 |
tim |
1.10 |
* @param w the worker |
357 |
dl |
1.2 |
*/ |
358 |
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private void workerDone(Worker w) { |
359 |
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boolean allDone = false; |
360 |
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mainLock.lock(); |
361 |
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try { |
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completedTaskCount += w.completedTasks; |
363 |
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workers.remove(w); |
364 |
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|
365 |
tim |
1.10 |
if (--poolSize > 0) |
366 |
dl |
1.2 |
return; |
367 |
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|
368 |
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// If this was last thread, deal with potential shutdown |
369 |
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int stat = shutdownStatus; |
370 |
tim |
1.10 |
|
371 |
dl |
1.2 |
// If there are queued tasks but no threads, create replacement. |
372 |
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if (stat != SHUTDOWN_NOW) { |
373 |
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Runnable r = workQueue.poll(); |
374 |
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if (r != null) { |
375 |
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addThread(r).start(); |
376 |
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return; |
377 |
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} |
378 |
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} |
379 |
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|
380 |
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// if no tasks and not shutdown, can exit without replacement |
381 |
tim |
1.10 |
if (stat == NOT_SHUTDOWN) |
382 |
dl |
1.2 |
return; |
383 |
|
|
|
384 |
|
|
allDone = true; |
385 |
|
|
isTerminated = true; |
386 |
|
|
termination.signalAll(); |
387 |
tim |
1.14 |
} finally { |
388 |
dl |
1.2 |
mainLock.unlock(); |
389 |
|
|
} |
390 |
|
|
|
391 |
|
|
if (allDone) // call outside lock |
392 |
|
|
terminated(); |
393 |
|
|
} |
394 |
|
|
|
395 |
|
|
/** |
396 |
tim |
1.10 |
* Worker threads |
397 |
dl |
1.2 |
*/ |
398 |
|
|
private class Worker implements Runnable { |
399 |
|
|
|
400 |
|
|
/** |
401 |
|
|
* The runLock is acquired and released surrounding each task |
402 |
|
|
* execution. It mainly protects against interrupts that are |
403 |
|
|
* intended to cancel the worker thread from instead |
404 |
|
|
* interrupting the task being run. |
405 |
|
|
*/ |
406 |
|
|
private final ReentrantLock runLock = new ReentrantLock(); |
407 |
|
|
|
408 |
|
|
/** |
409 |
|
|
* Initial task to run before entering run loop |
410 |
|
|
*/ |
411 |
|
|
private Runnable firstTask; |
412 |
|
|
|
413 |
|
|
/** |
414 |
|
|
* Per thread completed task counter; accumulated |
415 |
|
|
* into completedTaskCount upon termination. |
416 |
|
|
*/ |
417 |
|
|
volatile long completedTasks; |
418 |
|
|
|
419 |
|
|
/** |
420 |
|
|
* Thread this worker is running in. Acts as a final field, |
421 |
|
|
* but cannot be set until thread is created. |
422 |
|
|
*/ |
423 |
|
|
Thread thread; |
424 |
|
|
|
425 |
|
|
Worker(Runnable firstTask) { |
426 |
|
|
this.firstTask = firstTask; |
427 |
|
|
} |
428 |
|
|
|
429 |
|
|
boolean isActive() { |
430 |
|
|
return runLock.isLocked(); |
431 |
|
|
} |
432 |
|
|
|
433 |
|
|
/** |
434 |
|
|
* Interrupt thread if not running a task |
435 |
tim |
1.10 |
*/ |
436 |
dl |
1.2 |
void interruptIfIdle() { |
437 |
|
|
if (runLock.tryLock()) { |
438 |
|
|
try { |
439 |
|
|
thread.interrupt(); |
440 |
tim |
1.14 |
} finally { |
441 |
dl |
1.2 |
runLock.unlock(); |
442 |
|
|
} |
443 |
|
|
} |
444 |
|
|
} |
445 |
|
|
|
446 |
|
|
/** |
447 |
|
|
* Cause thread to die even if running a task. |
448 |
tim |
1.10 |
*/ |
449 |
dl |
1.2 |
void interruptNow() { |
450 |
|
|
thread.interrupt(); |
451 |
|
|
} |
452 |
|
|
|
453 |
|
|
/** |
454 |
|
|
* Run a single task between before/after methods. |
455 |
|
|
*/ |
456 |
|
|
private void runTask(Runnable task) { |
457 |
|
|
runLock.lock(); |
458 |
|
|
try { |
459 |
|
|
// Abort now if immediate cancel. Otherwise, we have |
460 |
|
|
// committed to run this task. |
461 |
|
|
if (shutdownStatus == SHUTDOWN_NOW) |
462 |
|
|
return; |
463 |
|
|
|
464 |
|
|
Thread.interrupted(); // clear interrupt status on entry |
465 |
|
|
boolean ran = false; |
466 |
|
|
beforeExecute(thread, task); |
467 |
|
|
try { |
468 |
|
|
task.run(); |
469 |
|
|
ran = true; |
470 |
|
|
afterExecute(task, null); |
471 |
|
|
++completedTasks; |
472 |
tim |
1.14 |
} catch(RuntimeException ex) { |
473 |
dl |
1.2 |
if (!ran) |
474 |
|
|
afterExecute(task, ex); |
475 |
|
|
// else the exception occurred within |
476 |
|
|
// afterExecute itself in which case we don't |
477 |
|
|
// want to call it again. |
478 |
|
|
throw ex; |
479 |
|
|
} |
480 |
tim |
1.14 |
} finally { |
481 |
dl |
1.2 |
runLock.unlock(); |
482 |
|
|
} |
483 |
|
|
} |
484 |
|
|
|
485 |
|
|
/** |
486 |
|
|
* Main run loop |
487 |
|
|
*/ |
488 |
|
|
public void run() { |
489 |
|
|
try { |
490 |
|
|
for (;;) { |
491 |
|
|
Runnable task; |
492 |
|
|
if (firstTask != null) { |
493 |
|
|
task = firstTask; |
494 |
|
|
firstTask = null; |
495 |
tim |
1.14 |
} else { |
496 |
dl |
1.2 |
task = getTask(); |
497 |
|
|
if (task == null) |
498 |
|
|
break; |
499 |
|
|
} |
500 |
|
|
runTask(task); |
501 |
|
|
task = null; // unnecessary but can help GC |
502 |
|
|
} |
503 |
tim |
1.14 |
} catch(InterruptedException ie) { |
504 |
dl |
1.2 |
// fall through |
505 |
tim |
1.14 |
} finally { |
506 |
dl |
1.2 |
workerDone(this); |
507 |
|
|
} |
508 |
|
|
} |
509 |
|
|
} |
510 |
tim |
1.1 |
|
511 |
|
|
/** |
512 |
|
|
* Creates a new <tt>ThreadPoolExecutor</tt> with the given initial |
513 |
|
|
* parameters. It may be more convenient to use one of the factory |
514 |
|
|
* methods instead of this general purpose constructor. |
515 |
|
|
* |
516 |
dl |
1.2 |
* @param corePoolSize the number of threads to keep in the |
517 |
tim |
1.1 |
* pool, even if they are idle. |
518 |
dl |
1.2 |
* @param maximumPoolSize the maximum number of threads to allow in the |
519 |
tim |
1.1 |
* pool. |
520 |
|
|
* @param keepAliveTime when the number of threads is greater than |
521 |
dl |
1.2 |
* the core, this is the maximum time that excess idle threads |
522 |
tim |
1.1 |
* will wait for new tasks before terminating. |
523 |
dl |
1.2 |
* @param unit the time unit for the keepAliveTime |
524 |
tim |
1.1 |
* argument. |
525 |
|
|
* @param workQueue the queue to use for holding tasks before the |
526 |
|
|
* are executed. This queue will hold only the <tt>Runnable</tt> |
527 |
|
|
* tasks submitted by the <tt>execute</tt> method. |
528 |
dl |
1.2 |
* @throws IllegalArgumentException if corePoolSize, or |
529 |
|
|
* keepAliveTime less than zero, or if maximumPoolSize less than or |
530 |
|
|
* equal to zero, or if corePoolSize greater than maximumPoolSize. |
531 |
tim |
1.1 |
* @throws NullPointerException if <tt>workQueue</tt> is null |
532 |
|
|
*/ |
533 |
dl |
1.2 |
public ThreadPoolExecutor(int corePoolSize, |
534 |
|
|
int maximumPoolSize, |
535 |
tim |
1.1 |
long keepAliveTime, |
536 |
dl |
1.2 |
TimeUnit unit, |
537 |
|
|
BlockingQueue<Runnable> workQueue) { |
538 |
tim |
1.10 |
this(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue, |
539 |
dl |
1.2 |
defaultThreadFactory, defaultHandler); |
540 |
|
|
} |
541 |
tim |
1.1 |
|
542 |
dl |
1.2 |
/** |
543 |
|
|
* Creates a new <tt>ThreadPoolExecutor</tt> with the given initial |
544 |
|
|
* parameters. |
545 |
|
|
* |
546 |
|
|
* @param corePoolSize the number of threads to keep in the |
547 |
|
|
* pool, even if they are idle. |
548 |
|
|
* @param maximumPoolSize the maximum number of threads to allow in the |
549 |
|
|
* pool. |
550 |
|
|
* @param keepAliveTime when the number of threads is greater than |
551 |
|
|
* the core, this is the maximum time that excess idle threads |
552 |
|
|
* will wait for new tasks before terminating. |
553 |
|
|
* @param unit the time unit for the keepAliveTime |
554 |
|
|
* argument. |
555 |
|
|
* @param workQueue the queue to use for holding tasks before the |
556 |
|
|
* are executed. This queue will hold only the <tt>Runnable</tt> |
557 |
|
|
* tasks submitted by the <tt>execute</tt> method. |
558 |
|
|
* @param threadFactory the factory to use when the executor |
559 |
tim |
1.10 |
* creates a new thread. |
560 |
dl |
1.2 |
* @throws IllegalArgumentException if corePoolSize, or |
561 |
|
|
* keepAliveTime less than zero, or if maximumPoolSize less than or |
562 |
|
|
* equal to zero, or if corePoolSize greater than maximumPoolSize. |
563 |
tim |
1.10 |
* @throws NullPointerException if <tt>workQueue</tt> |
564 |
dl |
1.2 |
* or <tt>threadFactory</tt> are null. |
565 |
|
|
*/ |
566 |
|
|
public ThreadPoolExecutor(int corePoolSize, |
567 |
|
|
int maximumPoolSize, |
568 |
|
|
long keepAliveTime, |
569 |
|
|
TimeUnit unit, |
570 |
|
|
BlockingQueue<Runnable> workQueue, |
571 |
|
|
ThreadFactory threadFactory) { |
572 |
tim |
1.1 |
|
573 |
tim |
1.10 |
this(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue, |
574 |
dl |
1.2 |
threadFactory, defaultHandler); |
575 |
|
|
} |
576 |
tim |
1.1 |
|
577 |
dl |
1.2 |
/** |
578 |
|
|
* Creates a new <tt>ThreadPoolExecutor</tt> with the given initial |
579 |
|
|
* parameters. |
580 |
|
|
* |
581 |
|
|
* @param corePoolSize the number of threads to keep in the |
582 |
|
|
* pool, even if they are idle. |
583 |
|
|
* @param maximumPoolSize the maximum number of threads to allow in the |
584 |
|
|
* pool. |
585 |
|
|
* @param keepAliveTime when the number of threads is greater than |
586 |
|
|
* the core, this is the maximum time that excess idle threads |
587 |
|
|
* will wait for new tasks before terminating. |
588 |
|
|
* @param unit the time unit for the keepAliveTime |
589 |
|
|
* argument. |
590 |
|
|
* @param workQueue the queue to use for holding tasks before the |
591 |
|
|
* are executed. This queue will hold only the <tt>Runnable</tt> |
592 |
|
|
* tasks submitted by the <tt>execute</tt> method. |
593 |
|
|
* @param handler the handler to use when execution is blocked |
594 |
|
|
* because the thread bounds and queue capacities are reached. |
595 |
|
|
* @throws IllegalArgumentException if corePoolSize, or |
596 |
|
|
* keepAliveTime less than zero, or if maximumPoolSize less than or |
597 |
|
|
* equal to zero, or if corePoolSize greater than maximumPoolSize. |
598 |
tim |
1.10 |
* @throws NullPointerException if <tt>workQueue</tt> |
599 |
dl |
1.2 |
* or <tt>handler</tt> are null. |
600 |
|
|
*/ |
601 |
|
|
public ThreadPoolExecutor(int corePoolSize, |
602 |
|
|
int maximumPoolSize, |
603 |
|
|
long keepAliveTime, |
604 |
|
|
TimeUnit unit, |
605 |
|
|
BlockingQueue<Runnable> workQueue, |
606 |
|
|
RejectedExecutionHandler handler) { |
607 |
tim |
1.10 |
this(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue, |
608 |
dl |
1.2 |
defaultThreadFactory, handler); |
609 |
|
|
} |
610 |
tim |
1.1 |
|
611 |
dl |
1.2 |
/** |
612 |
|
|
* Creates a new <tt>ThreadPoolExecutor</tt> with the given initial |
613 |
|
|
* parameters. |
614 |
|
|
* |
615 |
|
|
* @param corePoolSize the number of threads to keep in the |
616 |
|
|
* pool, even if they are idle. |
617 |
|
|
* @param maximumPoolSize the maximum number of threads to allow in the |
618 |
|
|
* pool. |
619 |
|
|
* @param keepAliveTime when the number of threads is greater than |
620 |
|
|
* the core, this is the maximum time that excess idle threads |
621 |
|
|
* will wait for new tasks before terminating. |
622 |
|
|
* @param unit the time unit for the keepAliveTime |
623 |
|
|
* argument. |
624 |
|
|
* @param workQueue the queue to use for holding tasks before the |
625 |
|
|
* are executed. This queue will hold only the <tt>Runnable</tt> |
626 |
|
|
* tasks submitted by the <tt>execute</tt> method. |
627 |
|
|
* @param threadFactory the factory to use when the executor |
628 |
tim |
1.10 |
* creates a new thread. |
629 |
dl |
1.2 |
* @param handler the handler to use when execution is blocked |
630 |
|
|
* because the thread bounds and queue capacities are reached. |
631 |
|
|
* @throws IllegalArgumentException if corePoolSize, or |
632 |
|
|
* keepAliveTime less than zero, or if maximumPoolSize less than or |
633 |
|
|
* equal to zero, or if corePoolSize greater than maximumPoolSize. |
634 |
tim |
1.10 |
* @throws NullPointerException if <tt>workQueue</tt> |
635 |
dl |
1.2 |
* or <tt>threadFactory</tt> or <tt>handler</tt> are null. |
636 |
|
|
*/ |
637 |
|
|
public ThreadPoolExecutor(int corePoolSize, |
638 |
|
|
int maximumPoolSize, |
639 |
|
|
long keepAliveTime, |
640 |
|
|
TimeUnit unit, |
641 |
|
|
BlockingQueue<Runnable> workQueue, |
642 |
|
|
ThreadFactory threadFactory, |
643 |
|
|
RejectedExecutionHandler handler) { |
644 |
tim |
1.10 |
if (corePoolSize < 0 || |
645 |
dl |
1.2 |
maximumPoolSize <= 0 || |
646 |
tim |
1.10 |
maximumPoolSize < corePoolSize || |
647 |
dl |
1.2 |
keepAliveTime < 0) |
648 |
|
|
throw new IllegalArgumentException(); |
649 |
|
|
if (workQueue == null || threadFactory == null || handler == null) |
650 |
|
|
throw new NullPointerException(); |
651 |
|
|
this.corePoolSize = corePoolSize; |
652 |
|
|
this.maximumPoolSize = maximumPoolSize; |
653 |
|
|
this.workQueue = workQueue; |
654 |
|
|
this.keepAliveTime = unit.toNanos(keepAliveTime); |
655 |
|
|
this.threadFactory = threadFactory; |
656 |
|
|
this.handler = handler; |
657 |
tim |
1.1 |
} |
658 |
|
|
|
659 |
dl |
1.2 |
|
660 |
|
|
/** |
661 |
|
|
* Executes the given task sometime in the future. The task |
662 |
|
|
* may execute in a new thread or in an existing pooled thread. |
663 |
|
|
* |
664 |
|
|
* If the task cannot be submitted for execution, either because this |
665 |
|
|
* executor has been shutdown or because its capacity has been reached, |
666 |
tim |
1.10 |
* the task is handled by the current <tt>RejectedExecutionHandler</tt>. |
667 |
dl |
1.2 |
* |
668 |
|
|
* @param command the task to execute |
669 |
|
|
* @throws RejectedExecutionException at discretion of |
670 |
dl |
1.8 |
* <tt>RejectedExecutionHandler</tt>, if task cannot be accepted |
671 |
|
|
* for execution |
672 |
dl |
1.2 |
*/ |
673 |
tim |
1.10 |
public void execute(Runnable command) { |
674 |
dl |
1.2 |
for (;;) { |
675 |
|
|
if (shutdownStatus != NOT_SHUTDOWN) { |
676 |
dl |
1.13 |
reject(command); |
677 |
dl |
1.2 |
return; |
678 |
|
|
} |
679 |
|
|
if (poolSize < corePoolSize && addIfUnderCorePoolSize(command)) |
680 |
|
|
return; |
681 |
|
|
if (workQueue.offer(command)) |
682 |
|
|
return; |
683 |
|
|
Runnable r = addIfUnderMaximumPoolSize(command); |
684 |
|
|
if (r == command) |
685 |
|
|
return; |
686 |
|
|
if (r == null) { |
687 |
dl |
1.13 |
reject(command); |
688 |
dl |
1.2 |
return; |
689 |
|
|
} |
690 |
|
|
// else retry |
691 |
|
|
} |
692 |
tim |
1.1 |
} |
693 |
dl |
1.4 |
|
694 |
dl |
1.2 |
public void shutdown() { |
695 |
|
|
mainLock.lock(); |
696 |
|
|
try { |
697 |
|
|
if (shutdownStatus == NOT_SHUTDOWN) // don't override shutdownNow |
698 |
|
|
shutdownStatus = SHUTDOWN_WHEN_IDLE; |
699 |
tim |
1.1 |
|
700 |
dl |
1.2 |
for (Iterator<Worker> it = workers.iterator(); it.hasNext(); ) |
701 |
|
|
it.next().interruptIfIdle(); |
702 |
tim |
1.14 |
} finally { |
703 |
dl |
1.2 |
mainLock.unlock(); |
704 |
|
|
} |
705 |
tim |
1.1 |
} |
706 |
|
|
|
707 |
dl |
1.2 |
public List shutdownNow() { |
708 |
|
|
mainLock.lock(); |
709 |
|
|
try { |
710 |
|
|
shutdownStatus = SHUTDOWN_NOW; |
711 |
|
|
for (Iterator<Worker> it = workers.iterator(); it.hasNext(); ) |
712 |
|
|
it.next().interruptNow(); |
713 |
tim |
1.14 |
} finally { |
714 |
dl |
1.2 |
mainLock.unlock(); |
715 |
|
|
} |
716 |
|
|
return Arrays.asList(workQueue.toArray()); |
717 |
tim |
1.1 |
} |
718 |
|
|
|
719 |
dl |
1.2 |
public boolean isShutdown() { |
720 |
|
|
return shutdownStatus != NOT_SHUTDOWN; |
721 |
tim |
1.1 |
} |
722 |
|
|
|
723 |
dl |
1.2 |
public boolean isTerminated() { |
724 |
|
|
return isTerminated; |
725 |
|
|
} |
726 |
tim |
1.1 |
|
727 |
dl |
1.2 |
public boolean awaitTermination(long timeout, TimeUnit unit) |
728 |
|
|
throws InterruptedException { |
729 |
|
|
mainLock.lock(); |
730 |
|
|
try { |
731 |
|
|
return termination.await(timeout, unit); |
732 |
tim |
1.14 |
} finally { |
733 |
dl |
1.2 |
mainLock.unlock(); |
734 |
|
|
} |
735 |
dl |
1.15 |
} |
736 |
|
|
|
737 |
|
|
/** |
738 |
|
|
* Invokes <tt>shutdown</tt> when this executor is no longer |
739 |
|
|
* referenced. |
740 |
|
|
*/ |
741 |
|
|
protected void finalize() { |
742 |
|
|
shutdown(); |
743 |
dl |
1.2 |
} |
744 |
tim |
1.10 |
|
745 |
dl |
1.2 |
/** |
746 |
|
|
* Sets the thread factory used to create new threads. |
747 |
|
|
* |
748 |
|
|
* @param threadFactory the new thread factory |
749 |
tim |
1.11 |
* @see #getThreadFactory |
750 |
dl |
1.2 |
*/ |
751 |
|
|
public void setThreadFactory(ThreadFactory threadFactory) { |
752 |
|
|
this.threadFactory = threadFactory; |
753 |
tim |
1.1 |
} |
754 |
|
|
|
755 |
dl |
1.2 |
/** |
756 |
|
|
* Returns the thread factory used to create new threads. |
757 |
|
|
* |
758 |
|
|
* @return the current thread factory |
759 |
tim |
1.11 |
* @see #setThreadFactory |
760 |
dl |
1.2 |
*/ |
761 |
|
|
public ThreadFactory getThreadFactory() { |
762 |
|
|
return threadFactory; |
763 |
tim |
1.1 |
} |
764 |
|
|
|
765 |
dl |
1.2 |
/** |
766 |
|
|
* Sets a new handler for unexecutable tasks. |
767 |
|
|
* |
768 |
|
|
* @param handler the new handler |
769 |
tim |
1.11 |
* @see #getRejectedExecutionHandler |
770 |
dl |
1.2 |
*/ |
771 |
|
|
public void setRejectedExecutionHandler(RejectedExecutionHandler handler) { |
772 |
|
|
this.handler = handler; |
773 |
|
|
} |
774 |
tim |
1.1 |
|
775 |
dl |
1.2 |
/** |
776 |
|
|
* Returns the current handler for unexecutable tasks. |
777 |
|
|
* |
778 |
|
|
* @return the current handler |
779 |
tim |
1.11 |
* @see #setRejectedExecutionHandler |
780 |
dl |
1.2 |
*/ |
781 |
|
|
public RejectedExecutionHandler getRejectedExecutionHandler() { |
782 |
|
|
return handler; |
783 |
tim |
1.1 |
} |
784 |
|
|
|
785 |
dl |
1.2 |
/** |
786 |
|
|
* Returns the task queue used by this executor. Note that |
787 |
|
|
* this queue may be in active use. Retrieveing the task queue |
788 |
|
|
* does not prevent queued tasks from executing. |
789 |
|
|
* |
790 |
|
|
* @return the task queue |
791 |
|
|
*/ |
792 |
|
|
public BlockingQueue<Runnable> getQueue() { |
793 |
|
|
return workQueue; |
794 |
tim |
1.1 |
} |
795 |
dl |
1.4 |
|
796 |
|
|
/** |
797 |
|
|
* Removes this task from internal queue if it is present, thus |
798 |
|
|
* causing it not to be run if it has not already started. This |
799 |
|
|
* method may be useful as one part of a cancellation scheme. |
800 |
tim |
1.10 |
* |
801 |
dl |
1.8 |
* @param task the task to remove |
802 |
|
|
* @return true if the task was removed |
803 |
dl |
1.4 |
*/ |
804 |
dl |
1.5 |
public boolean remove(Runnable task) { |
805 |
dl |
1.4 |
return getQueue().remove(task); |
806 |
|
|
} |
807 |
|
|
|
808 |
dl |
1.7 |
|
809 |
|
|
/** |
810 |
tim |
1.10 |
* Removes from the work queue all {@link Cancellable} tasks |
811 |
dl |
1.7 |
* that have been cancelled. This method can be useful as a |
812 |
|
|
* storage reclamation operation, that has no other impact |
813 |
|
|
* on functionality. Cancelled tasks are never executed, but |
814 |
|
|
* may accumulate in work queues until worker threads can |
815 |
|
|
* actively remove them. Invoking this method ensures that they |
816 |
|
|
* are instead removed now. |
817 |
|
|
*/ |
818 |
|
|
|
819 |
|
|
public void purge() { |
820 |
|
|
Iterator<Runnable> it = getQueue().iterator(); |
821 |
|
|
while (it.hasNext()) { |
822 |
|
|
Runnable r = it.next(); |
823 |
|
|
if (r instanceof Cancellable) { |
824 |
|
|
Cancellable c = (Cancellable)r; |
825 |
tim |
1.10 |
if (c.isCancelled()) |
826 |
dl |
1.7 |
it.remove(); |
827 |
|
|
} |
828 |
|
|
} |
829 |
|
|
} |
830 |
tim |
1.1 |
|
831 |
|
|
/** |
832 |
dl |
1.2 |
* Sets the core number of threads. This overrides any value set |
833 |
|
|
* in the constructor. If the new value is smaller than the |
834 |
|
|
* current value, excess existing threads will be terminated when |
835 |
|
|
* they next become idle. |
836 |
tim |
1.1 |
* |
837 |
dl |
1.2 |
* @param corePoolSize the new core size |
838 |
tim |
1.10 |
* @throws IllegalArgumentException if <tt>corePoolSize</tt> |
839 |
dl |
1.8 |
* less than zero |
840 |
tim |
1.11 |
* @see #getCorePoolSize |
841 |
tim |
1.1 |
*/ |
842 |
dl |
1.2 |
public void setCorePoolSize(int corePoolSize) { |
843 |
|
|
if (corePoolSize < 0) |
844 |
|
|
throw new IllegalArgumentException(); |
845 |
|
|
mainLock.lock(); |
846 |
|
|
try { |
847 |
|
|
int extra = this.corePoolSize - corePoolSize; |
848 |
|
|
this.corePoolSize = corePoolSize; |
849 |
|
|
if (extra > 0 && poolSize > corePoolSize) { |
850 |
|
|
Iterator<Worker> it = workers.iterator(); |
851 |
tim |
1.10 |
while (it.hasNext() && |
852 |
|
|
extra > 0 && |
853 |
dl |
1.2 |
poolSize > corePoolSize && |
854 |
|
|
workQueue.remainingCapacity() == 0) { |
855 |
|
|
it.next().interruptIfIdle(); |
856 |
|
|
--extra; |
857 |
|
|
} |
858 |
|
|
} |
859 |
tim |
1.10 |
|
860 |
tim |
1.14 |
} finally { |
861 |
dl |
1.2 |
mainLock.unlock(); |
862 |
|
|
} |
863 |
|
|
} |
864 |
tim |
1.1 |
|
865 |
|
|
/** |
866 |
dl |
1.2 |
* Returns the core number of threads. |
867 |
tim |
1.1 |
* |
868 |
dl |
1.2 |
* @return the core number of threads |
869 |
tim |
1.11 |
* @see #setCorePoolSize |
870 |
tim |
1.1 |
*/ |
871 |
tim |
1.10 |
public int getCorePoolSize() { |
872 |
dl |
1.2 |
return corePoolSize; |
873 |
|
|
} |
874 |
tim |
1.1 |
|
875 |
|
|
/** |
876 |
|
|
* Sets the maximum allowed number of threads. This overrides any |
877 |
dl |
1.2 |
* value set in the constructor. If the new value is smaller than |
878 |
|
|
* the current value, excess existing threads will be |
879 |
|
|
* terminated when they next become idle. |
880 |
tim |
1.1 |
* |
881 |
dl |
1.2 |
* @param maximumPoolSize the new maximum |
882 |
|
|
* @throws IllegalArgumentException if maximumPoolSize less than zero or |
883 |
|
|
* the {@link #getCorePoolSize core pool size} |
884 |
tim |
1.11 |
* @see #getMaximumPoolSize |
885 |
dl |
1.2 |
*/ |
886 |
|
|
public void setMaximumPoolSize(int maximumPoolSize) { |
887 |
|
|
if (maximumPoolSize <= 0 || maximumPoolSize < corePoolSize) |
888 |
|
|
throw new IllegalArgumentException(); |
889 |
|
|
mainLock.lock(); |
890 |
|
|
try { |
891 |
|
|
int extra = this.maximumPoolSize - maximumPoolSize; |
892 |
|
|
this.maximumPoolSize = maximumPoolSize; |
893 |
|
|
if (extra > 0 && poolSize > maximumPoolSize) { |
894 |
|
|
Iterator<Worker> it = workers.iterator(); |
895 |
tim |
1.10 |
while (it.hasNext() && |
896 |
|
|
extra > 0 && |
897 |
dl |
1.2 |
poolSize > maximumPoolSize) { |
898 |
|
|
it.next().interruptIfIdle(); |
899 |
|
|
--extra; |
900 |
|
|
} |
901 |
|
|
} |
902 |
tim |
1.14 |
} finally { |
903 |
dl |
1.2 |
mainLock.unlock(); |
904 |
|
|
} |
905 |
|
|
} |
906 |
tim |
1.1 |
|
907 |
|
|
/** |
908 |
|
|
* Returns the maximum allowed number of threads. |
909 |
|
|
* |
910 |
dl |
1.2 |
* @return the maximum allowed number of threads |
911 |
tim |
1.11 |
* @see #setMaximumPoolSize |
912 |
tim |
1.1 |
*/ |
913 |
tim |
1.10 |
public int getMaximumPoolSize() { |
914 |
dl |
1.2 |
return maximumPoolSize; |
915 |
|
|
} |
916 |
tim |
1.1 |
|
917 |
|
|
/** |
918 |
|
|
* Sets the time limit for which threads may remain idle before |
919 |
dl |
1.2 |
* being terminated. If there are more than the core number of |
920 |
tim |
1.1 |
* threads currently in the pool, after waiting this amount of |
921 |
|
|
* time without processing a task, excess threads will be |
922 |
|
|
* terminated. This overrides any value set in the constructor. |
923 |
|
|
* @param time the time to wait. A time value of zero will cause |
924 |
|
|
* excess threads to terminate immediately after executing tasks. |
925 |
dl |
1.2 |
* @param unit the time unit of the time argument |
926 |
tim |
1.1 |
* @throws IllegalArgumentException if msecs less than zero |
927 |
tim |
1.11 |
* @see #getKeepAliveTime |
928 |
tim |
1.1 |
*/ |
929 |
dl |
1.2 |
public void setKeepAliveTime(long time, TimeUnit unit) { |
930 |
|
|
if (time < 0) |
931 |
|
|
throw new IllegalArgumentException(); |
932 |
|
|
this.keepAliveTime = unit.toNanos(time); |
933 |
|
|
} |
934 |
tim |
1.1 |
|
935 |
|
|
/** |
936 |
|
|
* Returns the thread keep-alive time, which is the amount of time |
937 |
dl |
1.2 |
* which threads in excess of the core pool size may remain |
938 |
tim |
1.10 |
* idle before being terminated. |
939 |
tim |
1.1 |
* |
940 |
dl |
1.2 |
* @param unit the desired time unit of the result |
941 |
tim |
1.1 |
* @return the time limit |
942 |
tim |
1.11 |
* @see #setKeepAliveTime |
943 |
tim |
1.1 |
*/ |
944 |
tim |
1.10 |
public long getKeepAliveTime(TimeUnit unit) { |
945 |
dl |
1.2 |
return unit.convert(keepAliveTime, TimeUnit.NANOSECONDS); |
946 |
|
|
} |
947 |
tim |
1.1 |
|
948 |
|
|
/* Statistics */ |
949 |
|
|
|
950 |
|
|
/** |
951 |
|
|
* Returns the current number of threads in the pool. |
952 |
|
|
* |
953 |
|
|
* @return the number of threads |
954 |
|
|
*/ |
955 |
tim |
1.10 |
public int getPoolSize() { |
956 |
dl |
1.2 |
return poolSize; |
957 |
|
|
} |
958 |
tim |
1.1 |
|
959 |
|
|
/** |
960 |
dl |
1.2 |
* Returns the approximate number of threads that are actively |
961 |
tim |
1.1 |
* executing tasks. |
962 |
|
|
* |
963 |
|
|
* @return the number of threads |
964 |
|
|
*/ |
965 |
tim |
1.10 |
public int getActiveCount() { |
966 |
dl |
1.2 |
mainLock.lock(); |
967 |
|
|
try { |
968 |
|
|
int n = 0; |
969 |
|
|
for (Iterator<Worker> it = workers.iterator(); it.hasNext(); ) { |
970 |
|
|
if (it.next().isActive()) |
971 |
|
|
++n; |
972 |
|
|
} |
973 |
|
|
return n; |
974 |
tim |
1.14 |
} finally { |
975 |
dl |
1.2 |
mainLock.unlock(); |
976 |
|
|
} |
977 |
|
|
} |
978 |
tim |
1.1 |
|
979 |
|
|
/** |
980 |
dl |
1.2 |
* Returns the largest number of threads that have ever |
981 |
|
|
* simultaneously been in the pool. |
982 |
tim |
1.1 |
* |
983 |
|
|
* @return the number of threads |
984 |
|
|
*/ |
985 |
tim |
1.10 |
public int getLargestPoolSize() { |
986 |
dl |
1.2 |
mainLock.lock(); |
987 |
|
|
try { |
988 |
|
|
return largestPoolSize; |
989 |
tim |
1.14 |
} finally { |
990 |
dl |
1.2 |
mainLock.unlock(); |
991 |
|
|
} |
992 |
|
|
} |
993 |
tim |
1.1 |
|
994 |
|
|
/** |
995 |
dl |
1.2 |
* Returns the approximate total number of tasks that have been |
996 |
|
|
* scheduled for execution. Because the states of tasks and |
997 |
|
|
* threads may change dynamically during computation, the returned |
998 |
|
|
* value is only an approximation. |
999 |
tim |
1.1 |
* |
1000 |
|
|
* @return the number of tasks |
1001 |
|
|
*/ |
1002 |
tim |
1.10 |
public long getTaskCount() { |
1003 |
dl |
1.2 |
mainLock.lock(); |
1004 |
|
|
try { |
1005 |
|
|
long n = completedTaskCount; |
1006 |
|
|
for (Iterator<Worker> it = workers.iterator(); it.hasNext(); ) { |
1007 |
|
|
Worker w = it.next(); |
1008 |
|
|
n += w.completedTasks; |
1009 |
|
|
if (w.isActive()) |
1010 |
|
|
++n; |
1011 |
|
|
} |
1012 |
|
|
return n + workQueue.size(); |
1013 |
tim |
1.14 |
} finally { |
1014 |
dl |
1.2 |
mainLock.unlock(); |
1015 |
|
|
} |
1016 |
|
|
} |
1017 |
tim |
1.1 |
|
1018 |
|
|
/** |
1019 |
dl |
1.2 |
* Returns the approximate total number of tasks that have |
1020 |
|
|
* completed execution. Because the states of tasks and threads |
1021 |
|
|
* may change dynamically during computation, the returned value |
1022 |
|
|
* is only an approximation. |
1023 |
tim |
1.1 |
* |
1024 |
|
|
* @return the number of tasks |
1025 |
|
|
*/ |
1026 |
tim |
1.10 |
public long getCompletedTaskCount() { |
1027 |
dl |
1.2 |
mainLock.lock(); |
1028 |
|
|
try { |
1029 |
|
|
long n = completedTaskCount; |
1030 |
tim |
1.10 |
for (Iterator<Worker> it = workers.iterator(); it.hasNext(); ) |
1031 |
dl |
1.2 |
n += it.next().completedTasks; |
1032 |
|
|
return n; |
1033 |
tim |
1.14 |
} finally { |
1034 |
dl |
1.2 |
mainLock.unlock(); |
1035 |
|
|
} |
1036 |
|
|
} |
1037 |
tim |
1.1 |
|
1038 |
|
|
/** |
1039 |
dl |
1.2 |
* Method invoked prior to executing the given Runnable in given |
1040 |
|
|
* thread. This method may be used to re-initialize ThreadLocals, |
1041 |
dl |
1.5 |
* or to perform logging. Note: To properly nest multiple |
1042 |
|
|
* overridings, subclasses should generally invoke |
1043 |
|
|
* <tt>super.beforeExecute</tt> at the end of this method. |
1044 |
tim |
1.1 |
* |
1045 |
dl |
1.2 |
* @param t the thread that will run task r. |
1046 |
|
|
* @param r the task that will be executed. |
1047 |
tim |
1.1 |
*/ |
1048 |
dl |
1.2 |
protected void beforeExecute(Thread t, Runnable r) { } |
1049 |
tim |
1.1 |
|
1050 |
|
|
/** |
1051 |
dl |
1.2 |
* Method invoked upon completion of execution of the given |
1052 |
|
|
* Runnable. If non-null, the Throwable is the uncaught exception |
1053 |
dl |
1.5 |
* that caused execution to terminate abruptly. Note: To properly |
1054 |
|
|
* nest multiple overridings, subclasses should generally invoke |
1055 |
|
|
* <tt>super.afterExecute</tt> at the beginning of this method. |
1056 |
tim |
1.1 |
* |
1057 |
dl |
1.2 |
* @param r the runnable that has completed. |
1058 |
|
|
* @param t the exception that cause termination, or null if |
1059 |
|
|
* execution completed normally. |
1060 |
tim |
1.1 |
*/ |
1061 |
dl |
1.2 |
protected void afterExecute(Runnable r, Throwable t) { } |
1062 |
tim |
1.1 |
|
1063 |
dl |
1.2 |
/** |
1064 |
|
|
* Method invoked when the Executor has terminated. Default |
1065 |
|
|
* implementation does nothing. |
1066 |
|
|
*/ |
1067 |
|
|
protected void terminated() { } |
1068 |
tim |
1.1 |
|
1069 |
|
|
/** |
1070 |
|
|
* A handler for unexecutable tasks that runs these tasks directly in the |
1071 |
|
|
* calling thread of the <tt>execute</tt> method. This is the default |
1072 |
dl |
1.2 |
* <tt>RejectedExecutionHandler</tt>. |
1073 |
tim |
1.1 |
*/ |
1074 |
dl |
1.2 |
public static class CallerRunsPolicy implements RejectedExecutionHandler { |
1075 |
tim |
1.1 |
|
1076 |
|
|
/** |
1077 |
|
|
* Constructs a <tt>CallerRunsPolicy</tt>. |
1078 |
|
|
*/ |
1079 |
|
|
public CallerRunsPolicy() { } |
1080 |
|
|
|
1081 |
dl |
1.2 |
public void rejectedExecution(Runnable r, ThreadPoolExecutor e) { |
1082 |
|
|
if (!e.isShutdown()) { |
1083 |
tim |
1.1 |
r.run(); |
1084 |
|
|
} |
1085 |
|
|
} |
1086 |
|
|
} |
1087 |
|
|
|
1088 |
|
|
/** |
1089 |
dl |
1.8 |
* A handler for unexecutable tasks that throws a |
1090 |
|
|
* <tt>RejectedExecutionException</tt>. |
1091 |
tim |
1.1 |
*/ |
1092 |
dl |
1.2 |
public static class AbortPolicy implements RejectedExecutionHandler { |
1093 |
tim |
1.1 |
|
1094 |
|
|
/** |
1095 |
|
|
* Constructs a <tt>AbortPolicy</tt>. |
1096 |
|
|
*/ |
1097 |
|
|
public AbortPolicy() { } |
1098 |
|
|
|
1099 |
dl |
1.2 |
public void rejectedExecution(Runnable r, ThreadPoolExecutor e) { |
1100 |
|
|
throw new RejectedExecutionException(); |
1101 |
tim |
1.1 |
} |
1102 |
|
|
} |
1103 |
|
|
|
1104 |
|
|
/** |
1105 |
|
|
* A handler for unexecutable tasks that waits until the task can be |
1106 |
|
|
* submitted for execution. |
1107 |
|
|
*/ |
1108 |
dl |
1.2 |
public static class WaitPolicy implements RejectedExecutionHandler { |
1109 |
tim |
1.1 |
/** |
1110 |
|
|
* Constructs a <tt>WaitPolicy</tt>. |
1111 |
|
|
*/ |
1112 |
|
|
public WaitPolicy() { } |
1113 |
|
|
|
1114 |
dl |
1.2 |
public void rejectedExecution(Runnable r, ThreadPoolExecutor e) { |
1115 |
|
|
if (!e.isShutdown()) { |
1116 |
|
|
try { |
1117 |
|
|
e.getQueue().put(r); |
1118 |
tim |
1.14 |
} catch (InterruptedException ie) { |
1119 |
dl |
1.2 |
Thread.currentThread().interrupt(); |
1120 |
|
|
throw new RejectedExecutionException(ie); |
1121 |
|
|
} |
1122 |
tim |
1.1 |
} |
1123 |
|
|
} |
1124 |
|
|
} |
1125 |
|
|
|
1126 |
|
|
/** |
1127 |
|
|
* A handler for unexecutable tasks that silently discards these tasks. |
1128 |
|
|
*/ |
1129 |
dl |
1.2 |
public static class DiscardPolicy implements RejectedExecutionHandler { |
1130 |
tim |
1.1 |
|
1131 |
|
|
/** |
1132 |
|
|
* Constructs <tt>DiscardPolicy</tt>. |
1133 |
|
|
*/ |
1134 |
|
|
public DiscardPolicy() { } |
1135 |
|
|
|
1136 |
dl |
1.2 |
public void rejectedExecution(Runnable r, ThreadPoolExecutor e) { |
1137 |
tim |
1.1 |
} |
1138 |
|
|
} |
1139 |
|
|
|
1140 |
|
|
/** |
1141 |
dl |
1.8 |
* A handler for unexecutable tasks that discards the oldest |
1142 |
|
|
* unhandled request. |
1143 |
tim |
1.1 |
*/ |
1144 |
dl |
1.2 |
public static class DiscardOldestPolicy implements RejectedExecutionHandler { |
1145 |
tim |
1.1 |
/** |
1146 |
dl |
1.2 |
* Constructs a <tt>DiscardOldestPolicy</tt> for the given executor. |
1147 |
tim |
1.1 |
*/ |
1148 |
|
|
public DiscardOldestPolicy() { } |
1149 |
|
|
|
1150 |
dl |
1.2 |
public void rejectedExecution(Runnable r, ThreadPoolExecutor e) { |
1151 |
|
|
if (!e.isShutdown()) { |
1152 |
|
|
e.getQueue().poll(); |
1153 |
|
|
e.execute(r); |
1154 |
tim |
1.1 |
} |
1155 |
|
|
} |
1156 |
|
|
} |
1157 |
|
|
} |