com.buaa.cfs.nfs3.AsyncDataService.java Source code

Introduction

Here is the source code for com.buaa.cfs.nfs3.AsyncDataService.java

Source

/**
 * 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.
 */
package com.buaa.cfs.nfs3;

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

import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;

/**
 * This class is a thread pool to easily schedule async data operations. Current
 * async data operation is write back operation. In the future, we could use it
 * for readahead operations too.
 */
public class AsyncDataService {
    static final Log LOG = LogFactory.getLog(AsyncDataService.class);

    // ThreadPool core pool size
    private static final int CORE_THREADS_PER_VOLUME = 1;
    // ThreadPool maximum pool size
    private static final int MAXIMUM_THREADS_PER_VOLUME = 4;
    // ThreadPool keep-alive time for threads over core pool size
    private static final long THREADS_KEEP_ALIVE_SECONDS = 60;
    private final ThreadGroup threadGroup = new ThreadGroup("async data service");
    private ThreadFactory threadFactory = null;
    private ThreadPoolExecutor executor = null;

    public AsyncDataService() {
        threadFactory = new ThreadFactory() {
            @Override
            public Thread newThread(Runnable r) {
                return new Thread(threadGroup, r);
            }
        };

        executor = new ThreadPoolExecutor(CORE_THREADS_PER_VOLUME, MAXIMUM_THREADS_PER_VOLUME,
                THREADS_KEEP_ALIVE_SECONDS, TimeUnit.SECONDS, new LinkedBlockingQueue<Runnable>(), threadFactory);

        // This can reduce the number of running threads
        executor.allowCoreThreadTimeOut(true);
    }

    /**
     * Execute the task sometime in the future.
     */
    synchronized void execute(Runnable task) {
        if (executor == null) {
            throw new RuntimeException("AsyncDataService is already shutdown");
        }
        if (LOG.isDebugEnabled()) {
            LOG.debug("Current active thread number: " + executor.getActiveCount() + " queue size: "
                    + executor.getQueue().size() + " scheduled task number: " + executor.getTaskCount());
        }
        executor.execute(task);
    }

    /**
     * Gracefully shut down the ThreadPool. Will wait for all data tasks to
     * finish.
     */
    synchronized void shutdown() {
        if (executor == null) {
            LOG.warn("AsyncDataService has already shut down.");
        } else {
            LOG.info("Shutting down all async data service threads...");
            executor.shutdown();

            // clear the executor so that calling execute again will fail.
            executor = null;
            LOG.info("All async data service threads have been shut down");
        }
    }

    /**
     * Write the data to HDFS asynchronously
     */
    void writeAsync(OpenFileCtx openFileCtx) {
        if (LOG.isDebugEnabled()) {
            LOG.debug("Scheduling write back task for fileId: " + openFileCtx.getLatestAttr().getFileId());
        }
        WriteBackTask wbTask = new WriteBackTask(openFileCtx);
        execute(wbTask);
    }

    /**
     * A task to write data back to HDFS for a file. Since only one thread can
     * write to a file, there should only be one task at any time for a file
     * (in queue or executing), and this should be guaranteed by the caller.
     */
    static class WriteBackTask implements Runnable {

        OpenFileCtx openFileCtx;

        WriteBackTask(OpenFileCtx openFileCtx) {
            this.openFileCtx = openFileCtx;
        }

        OpenFileCtx getOpenFileCtx() {
            return openFileCtx;
        }

        @Override
        public String toString() {
            // Called in AsyncDataService.execute for displaying error messages.
            return "write back data for fileId" + openFileCtx.getLatestAttr().getFileId() + " with nextOffset "
                    + openFileCtx.getNextOffset();
        }

        @Override
        public void run() {
            try {
                openFileCtx.executeWriteBack();
            } catch (Throwable t) {
                LOG.error("Async data service got error: ", t);
            }
        }
    }
}