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This artifact provides a single jar that contains all classes required to use remote EJB and JMS, including all dependencies. It is intended for use by those not using maven, maven users should just import the EJB and JMS BOM's instead (shaded JAR's cause lots of problems with maven, as it is very easy to inadvertently end up with different versions on classes on the class path).

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/*
 * JBoss, Home of Professional Open Source.
 * Copyright 2017 Red Hat, Inc., and individual contributors
 * as indicated by the @author tags.
 *
 * 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 org.jboss.threads;

import java.util.ArrayDeque;
import java.util.concurrent.Executor;
import java.util.concurrent.RejectedExecutionException;

import org.wildfly.common.Assert;

/**
 * An executor for long-running tasks which limits the total concurrency over a delegate thread pool.
 *
 * @author David M. Lloyd
 */
public class LimitedExecutor implements Executor {
    private final Executor executor;
    private final Thread.UncaughtExceptionHandler handler;
    private final int concurrencyLimit;
    private final Runner runner;

    public LimitedExecutor(final Executor executor, final Thread.UncaughtExceptionHandler handler, final int concurrencyLimit) {
        this.executor = executor;
        this.handler = handler;
        this.concurrencyLimit = concurrencyLimit;
        this.runner = new Runner();
    }

    public LimitedExecutor(final Executor executor, final int concurrencyLimit) {
        this(executor, null, concurrencyLimit);
    }

    public void execute(final Runnable command) throws RejectedExecutionException {
        Assert.checkNotNullParam("command", command);
        runner.add(command);
    }

    @SuppressWarnings("serial")
    class Runner extends ArrayDeque implements Runnable {
        private int runCount;

        public synchronized boolean add(final Runnable runnable) {
            int runCount = this.runCount;
            if (runCount < concurrencyLimit) {
                executor.execute(this);
                this.runCount = runCount + 1;
            }
            return super.add(runnable);
        }

        public void run() {
            Runnable task;
            for (;;) {
                synchronized (this) {
                    task = poll();
                    if (task == null) {
                        runCount--;
                        return;
                    }
                }
                try {
                    task.run();
                } catch (Throwable t) {
                    final Thread.UncaughtExceptionHandler handler = LimitedExecutor.this.handler;
                    if (handler != null) try {
                        handler.uncaughtException(Thread.currentThread(), t);
                    } catch (Throwable ignored) {}
                }
            }
        }

        public String toString() {
            return String.format("Task runner for %s", LimitedExecutor.this);
        }
    }

    public String toString() {
        return String.format("Limited executor (%d tasks) over %s", Integer.valueOf(concurrencyLimit), executor);
    }
}