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The AWS SDK for Java with support for OSGi. The AWS SDK for Java provides Java APIs for building software on AWS' cost-effective, scalable, and reliable infrastructure products. The AWS Java SDK allows developers to code against APIs for all of Amazon's infrastructure web services (Amazon S3, Amazon EC2, Amazon SQS, Amazon Relational Database Service, Amazon AutoScaling, etc).

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/*
 * Copyright 2015-2016 Amazon.com, Inc. or its affiliates. All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License").
 * You may not use this file except in compliance with the License.
 * A copy of the License is located at
 *
 *  http://aws.amazon.com/apache2.0
 *
 * or in the "license" file accompanying this file. This file 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 com.amazonaws.http.timers.request;

import java.util.concurrent.ScheduledFuture;
import java.util.concurrent.ScheduledThreadPoolExecutor;
import java.util.concurrent.TimeUnit;

import org.apache.http.client.methods.HttpRequestBase;

import com.amazonaws.annotation.SdkInternalApi;
import com.amazonaws.annotation.SdkTestInternalApi;
import com.amazonaws.annotation.ThreadSafe;
import com.amazonaws.http.timers.TimeoutThreadPoolBuilder;

/**
 * Represents a timer class to enforce HTTP request timeouts.
 */
@ThreadSafe
@SdkInternalApi
public class HttpRequestTimer {

    private volatile ScheduledThreadPoolExecutor executor;

    /**
     * Start the timer with the specified timeout and return a object that can be used to track the
     * state of the timer and cancel it if need be.
     *
     * @param apacheRequest
     *            HTTP request this timer will abort if triggered.
     * @param requestTimeoutMillis
     *            A positive value here enables the timer, a non-positive value disables it and
     *            returns a dummy tracker task
     * @return Implementation of {@link HttpRequestAbortTaskTrackerImpl} to query the state of the
     *         task and cancel it if appropriate
     */
    public HttpRequestAbortTaskTracker startTimer(final HttpRequestBase apacheRequest, final int requestTimeoutMillis) {
        if (isTimeoutDisabled(requestTimeoutMillis)) {
            return NoOpHttpRequestAbortTaskTracker.INSTANCE;
        } else if (executor == null) {
            initializeExecutor();
        }
        HttpRequestAbortTaskImpl timerTask = new HttpRequestAbortTaskImpl(apacheRequest);
        ScheduledFuture timerTaskFuture = executor.schedule(timerTask, requestTimeoutMillis, TimeUnit.MILLISECONDS);
        return new HttpRequestAbortTaskTrackerImpl(timerTask, timerTaskFuture);
    }

    private boolean isTimeoutDisabled(final int requestTimeoutMillis) {
        return requestTimeoutMillis <= 0;
    }

    /**
     * Executor is lazily initialized as it's not compatible with Java 6
     */
    private synchronized void initializeExecutor() {
        if (executor == null) {
            executor = TimeoutThreadPoolBuilder.buildDefaultTimeoutThreadPool();
        }
    }

    /**
     * Shutdown the underlying {@link ScheduledThreadPoolExecutor}. Should be invoked when
     * {@link AmazonHttpClient} is shutdown
     */
    public synchronized void shutdown() {
        if (executor != null) {
            executor.shutdown();
        }
    }

    /**
     * This method is current exposed for testing purposes
     * 
     * @return The underlying {@link ScheduledThreadPoolExecutor}
     */
    @SdkTestInternalApi
    public ScheduledThreadPoolExecutor getExecutor() {
        return executor;
    }

}