Java tutorial
/** * 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 org.apache.hadoop.mapred; import java.io.IOException; import java.util.concurrent.BlockingQueue; import java.util.concurrent.DelayQueue; import java.util.concurrent.Delayed; import java.util.concurrent.TimeUnit; import org.apache.commons.httpclient.HttpClient; import org.apache.commons.httpclient.HttpMethod; import org.apache.commons.httpclient.URI; import org.apache.commons.httpclient.methods.GetMethod; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; public class JobEndNotifier { private static final Log LOG = LogFactory.getLog(JobEndNotifier.class.getName()); private static Thread thread; private static volatile boolean running; private static BlockingQueue<JobEndStatusInfo> queue = new DelayQueue<JobEndStatusInfo>(); public static void startNotifier() { running = true; thread = new Thread(new Runnable() { public void run() { try { while (running) { sendNotification(queue.take()); } } catch (InterruptedException irex) { if (running) { LOG.error("Thread has ended unexpectedly", irex); } } } private void sendNotification(JobEndStatusInfo notification) { try { int code = httpNotification(notification.getUri()); if (code != 200) { throw new IOException("Invalid response status code: " + code); } } catch (IOException ioex) { LOG.error("Notification failure [" + notification + "]", ioex); if (notification.configureForRetry()) { try { queue.put(notification); } catch (InterruptedException iex) { LOG.error("Notification queuing error [" + notification + "]", iex); } } } catch (Exception ex) { LOG.error("Notification failure [" + notification + "]", ex); } } } ); thread.start(); } public static void stopNotifier() { running = false; thread.interrupt(); } private static JobEndStatusInfo createNotification(JobConf conf, JobStatus status) { JobEndStatusInfo notification = null; String uri = conf.getJobEndNotificationURI(); if (uri != null) { // +1 to make logic for first notification identical to a retry int retryAttempts = conf.getInt("job.end.retry.attempts", 0) + 1; long retryInterval = conf.getInt("job.end.retry.interval", 30000); if (uri.contains("$jobId")) { uri = uri.replace("$jobId", status.getJobID().toString()); } if (uri.contains("$jobStatus")) { String statusStr = (status.getRunState() == JobStatus.SUCCEEDED) ? "SUCCEEDED" : (status.getRunState() == JobStatus.FAILED) ? "FAILED" : "KILLED"; uri = uri.replace("$jobStatus", statusStr); } notification = new JobEndStatusInfo(uri, retryAttempts, retryInterval); } return notification; } public static void registerNotification(JobConf jobConf, JobStatus status) { JobEndStatusInfo notification = createNotification(jobConf, status); if (notification != null) { try { queue.put(notification); } catch (InterruptedException iex) { LOG.error("Notification queuing failure [" + notification + "]", iex); } } } private static int httpNotification(String uri) throws IOException { URI url = new URI(uri, false); HttpClient m_client = new HttpClient(); HttpMethod method = new GetMethod(url.getEscapedURI()); method.setRequestHeader("Accept", "*/*"); return m_client.executeMethod(method); } // for use by the LocalJobRunner, without using a thread&queue, // simple synchronous way public static void localRunnerNotification(JobConf conf, JobStatus status) { JobEndStatusInfo notification = createNotification(conf, status); if (notification != null) { while (notification.configureForRetry()) { try { int code = httpNotification(notification.getUri()); if (code != 200) { throw new IOException("Invalid response status code: " + code); } else { break; } } catch (IOException ioex) { LOG.error("Notification error [" + notification.getUri() + "]", ioex); } catch (Exception ex) { LOG.error("Notification error [" + notification.getUri() + "]", ex); } try { synchronized (Thread.currentThread()) { Thread.currentThread().sleep(notification.getRetryInterval()); } } catch (InterruptedException iex) { LOG.error("Notification retry error [" + notification + "]", iex); } } } } private static class JobEndStatusInfo implements Delayed { private String uri; private int retryAttempts; private long retryInterval; private long delayTime; JobEndStatusInfo(String uri, int retryAttempts, long retryInterval) { this.uri = uri; this.retryAttempts = retryAttempts; this.retryInterval = retryInterval; this.delayTime = System.currentTimeMillis(); } public String getUri() { return uri; } public int getRetryAttempts() { return retryAttempts; } public long getRetryInterval() { return retryInterval; } public long getDelayTime() { return delayTime; } public boolean configureForRetry() { boolean retry = false; if (getRetryAttempts() > 0) { retry = true; delayTime = System.currentTimeMillis() + retryInterval; } retryAttempts--; return retry; } public long getDelay(TimeUnit unit) { long n = this.delayTime - System.currentTimeMillis(); return unit.convert(n, TimeUnit.MILLISECONDS); } public int compareTo(Delayed d) { return (int) (delayTime - ((JobEndStatusInfo) d).delayTime); } @Override public boolean equals(Object o) { if (!(o instanceof JobEndStatusInfo)) { return false; } if (delayTime == ((JobEndStatusInfo) o).delayTime) { return true; } return false; } @Override public int hashCode() { return 37 * 17 + (int) (delayTime ^ (delayTime >>> 32)); } @Override public String toString() { return "URL: " + uri + " remaining retries: " + retryAttempts + " interval: " + retryInterval; } } }