13138848026

Committed 04 Feb 2025 02:53PM UTC coverage: 92.108% (+2.2%) from 89.877%

Build # 13138848026

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push

github

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mtf90

Commit Message

[maven-release-plugin] prepare release automatalib-0.12.0

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88.89

/commons/util/src/main/java/net/automatalib/common/util/concurrent/ScalingThreadPoolExecutor.java

/* Copyright (C) 2013-2025 TU Dortmund University
 * This file is part of AutomataLib <https://automatalib.net>.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package net.automatalib.common.util.concurrent;

import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.RejectedExecutionException;
import java.util.concurrent.RejectedExecutionHandler;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;

/**
 * A {@link ThreadPoolExecutor} that internally uses a {@link ScalingLinkedBlockingQueue} to manage scheduled tasks.
 * This allows us to manage a dynamically sized thread pool that actually spawns new threads when the pool still allows
 * for it.
 * <p>
 * Additionally, this implementation keeps track of the current number of active threads by using an
 * {@link AtomicInteger} counter, rather than querying its list of worker threads.
 * <p>
 * For further information, see
 * <a href="https://github.com/kimchy/kimchy.github.com/blob/master/_posts/2008-11-23-juc-executorservice-gotcha.textile">
 * this blog post</a>.
 */
public final class ScalingThreadPoolExecutor extends ThreadPoolExecutor {

    private final AtomicInteger activeCount = new AtomicInteger();

    public ScalingThreadPoolExecutor(int corePoolSize, int maximumPoolSize, long keepAliveTime, TimeUnit unit) {
        super(corePoolSize, maximumPoolSize, keepAliveTime, unit, new ScalingLinkedBlockingQueue());

        ((ScalingLinkedBlockingQueue) getQueue()).setTpe(this);
        setRejectedExecutionHandler(new ForceEnqueuingHandler());
    }

    @Override
    public int getActiveCount() {
        return activeCount.get();
    }

    @Override
    protected void beforeExecute(Thread t, Runnable r) {
        activeCount.incrementAndGet();
    }

    @Override
    protected void afterExecute(Runnable r, Throwable t) {
        activeCount.decrementAndGet();
    }

    /**
     * A modified {@link LinkedBlockingQueue} that rejects offering new elements if its associated
     * {@link ScalingThreadPoolExecutor} still has threads to spare. This means we will force a creation of a new thread
     * whenever there is room for parallel processing.
     * <p>
     * To prevent {@link RejectedExecutionException}s when reaching the limit of the thread pool, this class is only
     * useful in combination with a {@link ForceEnqueuingHandler} that forcefully enqueues the scheduled task to this
     * (otherwise unbounded) queue.
     */
    @SuppressWarnings("PMD.NonSerializableClass") // not publicly exposed
    private static final class ScalingLinkedBlockingQueue extends LinkedBlockingQueue<Runnable> {

        private ThreadPoolExecutor tpe;

        void setTpe(ThreadPoolExecutor tpe) {
            this.tpe = tpe;
        }

        @Override
        public boolean offer(Runnable r) {
            return tpe.getActiveCount() + size() >= tpe.getMaximumPoolSize() && super.offer(r);
        }
    }

    /**
     * A {@link RejectedExecutionHandler} that forces the enqueuing of rejected tasks to the queue of a
     * {@link ThreadPoolExecutor}. Mainly useful in combination with {@link ScalingLinkedBlockingQueue}.
     */
    private static final class ForceEnqueuingHandler implements RejectedExecutionHandler {

        @Override
        public void rejectedExecution(Runnable r, ThreadPoolExecutor executor) {
            try {
                executor.getQueue().put(r);
            } catch (InterruptedException e) {
                throw new RejectedExecutionException(e);
            }
        }
    }

}

1	/* Copyright (C) 2013-2025 TU Dortmund University
2	* This file is part of AutomataLib <https://automatalib.net>.
3	*
4	* Licensed under the Apache License, Version 2.0 (the "License");
5	* you may not use this file except in compliance with the License.
6	* You may obtain a copy of the License at
7	*
8	* http://www.apache.org/licenses/LICENSE-2.0
9	*
10	* Unless required by applicable law or agreed to in writing, software
11	* distributed under the License is distributed on an "AS IS" BASIS,
12	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13	* See the License for the specific language governing permissions and
14	* limitations under the License.
15	*/
16	package net.automatalib.common.util.concurrent;
17
18	import java.util.concurrent.LinkedBlockingQueue;
19	import java.util.concurrent.RejectedExecutionException;
20	import java.util.concurrent.RejectedExecutionHandler;
21	import java.util.concurrent.ThreadPoolExecutor;
22	import java.util.concurrent.TimeUnit;
23	import java.util.concurrent.atomic.AtomicInteger;
24
25	/**
26	* A {@link ThreadPoolExecutor} that internally uses a {@link ScalingLinkedBlockingQueue} to manage scheduled tasks.
27	* This allows us to manage a dynamically sized thread pool that actually spawns new threads when the pool still allows
28	* for it.
29	* <p>
30	* Additionally, this implementation keeps track of the current number of active threads by using an
31	* {@link AtomicInteger} counter, rather than querying its list of worker threads.
32	* <p>
33	* For further information, see
34	* <a href="https://github.com/kimchy/kimchy.github.com/blob/master/_posts/2008-11-23-juc-executorservice-gotcha.textile">
35	* this blog post</a>.
36	*/
37	public final class ScalingThreadPoolExecutor extends ThreadPoolExecutor {
38
39	private final AtomicInteger activeCount = new AtomicInteger();	2✔
40
41	public ScalingThreadPoolExecutor(int corePoolSize, int maximumPoolSize, long keepAliveTime, TimeUnit unit) {
42	super(corePoolSize, maximumPoolSize, keepAliveTime, unit, new ScalingLinkedBlockingQueue());	2✔
43
44	((ScalingLinkedBlockingQueue) getQueue()).setTpe(this);	2✔
45	setRejectedExecutionHandler(new ForceEnqueuingHandler());	2✔
46	}	2✔
47
48	@Override
49	public int getActiveCount() {
50	return activeCount.get();	2✔
51	}
52
53	@Override
54	protected void beforeExecute(Thread t, Runnable r) {
55	activeCount.incrementAndGet();	2✔
56	}	2✔
57
58	@Override
59	protected void afterExecute(Runnable r, Throwable t) {
60	activeCount.decrementAndGet();	2✔
61	}	2✔
62
63	/**
64	* A modified {@link LinkedBlockingQueue} that rejects offering new elements if its associated
65	* {@link ScalingThreadPoolExecutor} still has threads to spare. This means we will force a creation of a new thread
66	* whenever there is room for parallel processing.
67	* <p>
68	* To prevent {@link RejectedExecutionException}s when reaching the limit of the thread pool, this class is only
69	* useful in combination with a {@link ForceEnqueuingHandler} that forcefully enqueues the scheduled task to this
70	* (otherwise unbounded) queue.
71	*/
72	@SuppressWarnings("PMD.NonSerializableClass") // not publicly exposed
73	private static final class ScalingLinkedBlockingQueue extends LinkedBlockingQueue<Runnable> {
74
75	private ThreadPoolExecutor tpe;
76
77	void setTpe(ThreadPoolExecutor tpe) {
78	this.tpe = tpe;	2✔
79	}	2✔
80
81	@Override
82	public boolean offer(Runnable r) {
83	return tpe.getActiveCount() + size() >= tpe.getMaximumPoolSize() && super.offer(r);	2✔
84	}
85	}
86
87	/**
88	* A {@link RejectedExecutionHandler} that forces the enqueuing of rejected tasks to the queue of a
89	* {@link ThreadPoolExecutor}. Mainly useful in combination with {@link ScalingLinkedBlockingQueue}.
90	*/
91	private static final class ForceEnqueuingHandler implements RejectedExecutionHandler {
92
93	@Override
94	public void rejectedExecution(Runnable r, ThreadPoolExecutor executor) {
95	try {
96	executor.getQueue().put(r);	2✔
97	} catch (InterruptedException e) {	×
98	throw new RejectedExecutionException(e);	×
99	}	2✔
100	}	2✔
101	}
102
103	}

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