com.amazonaws.services.simpleworkflow.flow.worker.ActivityTaskPoller Maven / Gradle / Ivy

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The Amazon Web Services 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 2012-2014 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.services.simpleworkflow.flow.worker;

import java.lang.Thread.UncaughtExceptionHandler;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Semaphore;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import com.amazonaws.services.simpleworkflow.AmazonSimpleWorkflow;
import com.amazonaws.services.simpleworkflow.flow.generic.ActivityImplementationFactory;
import com.amazonaws.services.simpleworkflow.model.ActivityTask;
import com.amazonaws.services.simpleworkflow.model.WorkflowExecution;

public class ActivityTaskPoller extends SynchronousActivityTaskPoller {

    private static final Log log = LogFactory.getLog(ActivityTaskPoller.class);

    private ThreadPoolExecutor taskExecutorService;

    protected Semaphore pollSemaphore;

    private UncaughtExceptionHandler uncaughtExceptionHandler = new UncaughtExceptionHandler() {

        @Override
        public void uncaughtException(Thread t, Throwable e) {
            log.error("Failure in thread " + t.getName(), e);
        }
    };

    public ActivityTaskPoller(AmazonSimpleWorkflow service, String domain, String pollTaskList,
            ActivityImplementationFactory activityImplementationFactory, ThreadPoolExecutor taskExecutorService) {
        super(service, domain, pollTaskList, activityImplementationFactory);
        setTaskExecutorService(taskExecutorService);
    }

    public ExecutorService getTaskExecutorService() {
        return taskExecutorService;
    }

    public void setTaskExecutorService(ThreadPoolExecutor taskExecutorService) {
        this.taskExecutorService = taskExecutorService;
        pollSemaphore = new Semaphore(taskExecutorService.getMaximumPoolSize());
    }

    /**
     * Poll for a activity task and execute correspondent implementation using
     * provided executor service.
     * 
     * @return true if task was polled and decided upon, false if poll timed out
     * @throws Exception
     */
    @Override
    public boolean pollAndProcessSingleTask() throws Exception {
        boolean semaphoreNeedsRelease = false;
        try {
            // Without semaphore task that was polled from a service
            // can end up waiting on taskExecutor.execute(...) for a long
            // time leading to timeouts and other problems
            if (pollSemaphore != null) {
                pollSemaphore.acquire();
            }
            // we will release the semaphore in a finally clause
            semaphoreNeedsRelease = true;
            final ActivityTask task = poll();
            if (task == null) {
                return false;
            }
            semaphoreNeedsRelease = false;
            try {
                taskExecutorService.execute(new Runnable() {

                    @Override
                    public void run() {
                        try {
                            execute(task);
                        }
                        catch (Throwable ee) {
                            uncaughtExceptionHandler.uncaughtException(Thread.currentThread(), wrapFailure(task, ee));
                        }
                        finally {
                            pollSemaphore.release();
                        }
                    }
                });
            }
            catch (Exception e) {
                semaphoreNeedsRelease = true;
                throw e;
            } catch (Error e) {
                semaphoreNeedsRelease = true;
                throw e;
            }
        }
        finally {
            if (semaphoreNeedsRelease) {
                pollSemaphore.release();
            }
        }
        return true;
    }

    private Exception wrapFailure(final ActivityTask task, Throwable failure) {
        WorkflowExecution execution = task.getWorkflowExecution();

        RuntimeException e2 = new RuntimeException(
                "Failure taskId=\"" + task.getStartedEventId() + "\" workflowExecutionRunId=\"" + execution.getRunId()
                        + "\" workflowExecutionId=\"" + execution.getWorkflowId() + "\"", failure);
        return e2;
    }

    @Override
    public void shutdown() {
        taskExecutorService.shutdown();
    }

    @Override
    public void shutdownNow() {
        taskExecutorService.shutdownNow();
    }

    @Override
    public boolean awaitTermination(long timeout, TimeUnit unit) throws InterruptedException {
        return taskExecutorService.awaitTermination(timeout, unit);
    }
}