com.ibm.stocator.fs.cos.SemaphoredDelegatingExecutor.java Source code

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Here is the source code for com.ibm.stocator.fs.cos.SemaphoredDelegatingExecutor.java

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/*
 * Licensed to the Apache Software Foundation (ASF) under one
 *  or more contributor license agreements.  See the NOTICE file
 *  distributed with this work for additional information
 *  regarding copyright ownership.  The ASF licenses this file
 *  to you 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.
 *
 *  (C) Copyright IBM Corp. 2015, 2016
 */

package com.ibm.stocator.fs.cos;

import java.util.Collection;
import java.util.List;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Future;
import java.util.concurrent.Semaphore;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;

import com.google.common.util.concurrent.ForwardingListeningExecutorService;
import com.google.common.util.concurrent.Futures;
import com.google.common.util.concurrent.ListenableFuture;
import com.google.common.util.concurrent.ListeningExecutorService;

@SuppressWarnings("NullableProblems")
class SemaphoredDelegatingExecutor extends ForwardingListeningExecutorService {

    private final Semaphore queueingPermits;
    private final ListeningExecutorService executorDelegatee;
    private final int permitCount;

    /**
     * Instantiate
     *
     * @param executorDelegatee Executor to delegate to
     * @param permitCount number of permits into the queue permitted
     * @param fair should the semaphore be "fair"
     */
    SemaphoredDelegatingExecutor(ListeningExecutorService executorDelegateeT, int permitCountT, boolean fair) {
        permitCount = permitCountT;
        queueingPermits = new Semaphore(permitCount, fair);
        executorDelegatee = executorDelegateeT;
    }

    @Override
    protected ListeningExecutorService delegate() {
        return executorDelegatee;
    }

    @Override
    public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks) throws InterruptedException {
        throw new RuntimeException("Not implemented");
    }

    @Override
    public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks, long timeout, TimeUnit unit)
            throws InterruptedException {
        throw new RuntimeException("Not implemented");
    }

    @Override
    public <T> T invokeAny(Collection<? extends Callable<T>> tasks)
            throws InterruptedException, ExecutionException {
        throw new RuntimeException("Not implemented");
    }

    @Override
    public <T> T invokeAny(Collection<? extends Callable<T>> tasks, long timeout, TimeUnit unit)
            throws InterruptedException, ExecutionException, TimeoutException {
        throw new RuntimeException("Not implemented");
    }

    @Override
    public <T> ListenableFuture<T> submit(Callable<T> task) {
        try {
            queueingPermits.acquire();
        } catch (InterruptedException e) {
            Thread.currentThread().interrupt();
            return Futures.immediateFailedCheckedFuture(e);
        }
        return super.submit(new CallableWithPermitRelease<>(task));
    }

    @Override
    public <T> ListenableFuture<T> submit(Runnable task, T result) {
        try {
            queueingPermits.acquire();
        } catch (InterruptedException e) {
            Thread.currentThread().interrupt();
            return Futures.immediateFailedCheckedFuture(e);
        }
        return super.submit(new RunnableWithPermitRelease(task), result);
    }

    @Override
    public ListenableFuture<?> submit(Runnable task) {
        try {
            queueingPermits.acquire();
        } catch (InterruptedException e) {
            Thread.currentThread().interrupt();
            return Futures.immediateFailedCheckedFuture(e);
        }
        return super.submit(new RunnableWithPermitRelease(task));
    }

    @Override
    public void execute(Runnable command) {
        try {
            queueingPermits.acquire();
        } catch (InterruptedException e) {
            Thread.currentThread().interrupt();
        }
        super.execute(new RunnableWithPermitRelease(command));
    }

    /**
     * Get the number of permits available; guaranteed to be
     * {@code 0 <= availablePermits <= size}.
     *
     * @return the number of permits available at the time of invocation
     */
    public int getAvailablePermits() {
        return queueingPermits.availablePermits();
    }

    /**
     * Get the number of threads waiting to acquire a permit.
     *
     * @return snapshot of the length of the queue of blocked threads
     */
    public int getWaitingCount() {
        return queueingPermits.getQueueLength();
    }

    /**
     * Total number of permits.
     *
     * @return the number of permits as set in the constructor
     */
    public int getPermitCount() {
        return permitCount;
    }

    @Override
    public String toString() {
        final StringBuilder sb = new StringBuilder("SemaphoredDelegatingExecutor{");
        sb.append("permitCount=").append(getPermitCount());
        sb.append(", available=").append(getAvailablePermits());
        sb.append(", waiting=").append(getWaitingCount());
        sb.append('}');
        return sb.toString();
    }

    /**
     * Releases a permit after the task is executed.
     */
    class RunnableWithPermitRelease implements Runnable {

        private Runnable delegatee;

        public RunnableWithPermitRelease(Runnable delegateeT) {
            delegatee = delegateeT;
        }

        @Override
        public void run() {
            try {
                delegatee.run();
            } finally {
                queueingPermits.release();
            }

        }
    }

    /**
     * Releases a permit after the task is completed
     */
    class CallableWithPermitRelease<T> implements Callable<T> {

        private Callable<T> delegatee;

        public CallableWithPermitRelease(Callable<T> delegateeT) {
            delegatee = delegateeT;
        }

        @Override
        public T call() throws Exception {
            try {
                return delegatee.call();
            } finally {
                queueingPermits.release();
            }
        }
    }

}