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.mapreduce.lib.jobcontrol; import java.io.IOException; import java.util.ArrayList; import java.util.List; import org.apache.hadoop.classification.InterfaceAudience; import org.apache.hadoop.classification.InterfaceStability; import org.apache.hadoop.conf.Configuration; import org.apache.hadoop.fs.FileSystem; import org.apache.hadoop.fs.Path; import org.apache.hadoop.mapreduce.Job; import org.apache.hadoop.mapreduce.JobID; import org.apache.hadoop.mapreduce.lib.input.FileInputFormat; import org.apache.hadoop.util.StringUtils; import org.slf4j.Logger; import org.slf4j.LoggerFactory; /** * This class encapsulates a MapReduce job and its dependency. It monitors * the states of the depending jobs and updates the state of this job. * A job starts in the WAITING state. If it does not have any depending jobs, * or all of the depending jobs are in SUCCESS state, then the job state * will become READY. If any depending jobs fail, the job will fail too. * When in READY state, the job can be submitted to Hadoop for execution, with * the state changing into RUNNING state. From RUNNING state, the job * can get into SUCCESS or FAILED state, depending * the status of the job execution. */ @InterfaceAudience.Public @InterfaceStability.Evolving public class ControlledJob { private static final Logger LOG = LoggerFactory.getLogger(ControlledJob.class); // A job will be in one of the following states public enum State { SUCCESS, WAITING, RUNNING, READY, FAILED, DEPENDENT_FAILED }; public static final String CREATE_DIR = "mapreduce.jobcontrol.createdir.ifnotexist"; private State state; private String controlID; // assigned and used by JobControl class private Job job; // mapreduce job to be executed. // some info for human consumption, e.g. the reason why the job failed private String message; // the jobs the current job depends on private List<ControlledJob> dependingJobs; /** * Construct a job. * @param job a mapreduce job to be executed. * @param dependingJobs an array of jobs the current job depends on */ public ControlledJob(Job job, List<ControlledJob> dependingJobs) throws IOException { this.job = job; this.dependingJobs = dependingJobs; this.state = State.WAITING; this.controlID = "unassigned"; this.message = "just initialized"; } /** * Construct a job. * * @param conf mapred job configuration representing a job to be executed. * @throws IOException */ public ControlledJob(Configuration conf) throws IOException { this(Job.getInstance(conf), null); } @Override public String toString() { StringBuffer sb = new StringBuffer(); sb.append("job name:\t").append(this.job.getJobName()).append("\n"); sb.append("job id:\t").append(this.controlID).append("\n"); sb.append("job state:\t").append(this.state).append("\n"); sb.append("job mapred id:\t").append(this.job.getJobID()).append("\n"); sb.append("job message:\t").append(this.message).append("\n"); if (this.dependingJobs == null || this.dependingJobs.size() == 0) { sb.append("job has no depending job:\t").append("\n"); } else { sb.append("job has ").append(this.dependingJobs.size()).append(" dependeng jobs:\n"); for (int i = 0; i < this.dependingJobs.size(); i++) { sb.append("\t depending job ").append(i).append(":\t"); sb.append((this.dependingJobs.get(i)).getJobName()).append("\n"); } } return sb.toString(); } /** * @return the job name of this job */ public String getJobName() { return job.getJobName(); } /** * Set the job name for this job. * @param jobName the job name */ public void setJobName(String jobName) { job.setJobName(jobName); } /** * @return the job ID of this job assigned by JobControl */ public String getJobID() { return this.controlID; } /** * Set the job ID for this job. * @param id the job ID */ public void setJobID(String id) { this.controlID = id; } /** * @return the mapred ID of this job as assigned by the mapred framework. */ public synchronized JobID getMapredJobId() { return this.job.getJobID(); } /** * @return the mapreduce job */ public synchronized Job getJob() { return this.job; } /** * Set the mapreduce job * @param job the mapreduce job for this job. */ public synchronized void setJob(Job job) { this.job = job; } /** * @return the state of this job */ public synchronized State getJobState() { return this.state; } /** * Set the state for this job. * @param state the new state for this job. */ protected synchronized void setJobState(State state) { this.state = state; } /** * @return the message of this job */ public synchronized String getMessage() { return this.message; } /** * Set the message for this job. * @param message the message for this job. */ public synchronized void setMessage(String message) { this.message = message; } /** * @return the depending jobs of this job */ public List<ControlledJob> getDependentJobs() { return this.dependingJobs; } /** * Add a job to this jobs' dependency list. * Dependent jobs can only be added while a Job * is waiting to run, not during or afterwards. * * @param dependingJob Job that this Job depends on. * @return <tt>true</tt> if the Job was added. */ public synchronized boolean addDependingJob(ControlledJob dependingJob) { if (this.state == State.WAITING) { //only allowed to add jobs when waiting if (this.dependingJobs == null) { this.dependingJobs = new ArrayList<ControlledJob>(); } return this.dependingJobs.add(dependingJob); } else { return false; } } /** * @return true if this job is in a complete state */ public synchronized boolean isCompleted() { return this.state == State.FAILED || this.state == State.DEPENDENT_FAILED || this.state == State.SUCCESS; } /** * @return true if this job is in READY state */ public synchronized boolean isReady() { return this.state == State.READY; } public void killJob() throws IOException, InterruptedException { job.killJob(); } public synchronized void failJob(String message) throws IOException, InterruptedException { try { if (job != null && this.state == State.RUNNING) { job.killJob(); } } finally { this.state = State.FAILED; this.message = message; } } /** * Check the state of this running job. The state may * remain the same, become SUCCESS or FAILED. */ private void checkRunningState() throws IOException, InterruptedException { try { if (job.isComplete()) { if (job.isSuccessful()) { this.state = State.SUCCESS; } else { this.state = State.FAILED; this.message = "Job failed!"; } } } catch (IOException ioe) { this.state = State.FAILED; this.message = StringUtils.stringifyException(ioe); try { if (job != null) { job.killJob(); } } catch (IOException e) { } } } /** * Check and update the state of this job. The state changes * depending on its current state and the states of the depending jobs. */ synchronized State checkState() throws IOException, InterruptedException { if (this.state == State.RUNNING) { checkRunningState(); } if (this.state != State.WAITING) { return this.state; } if (this.dependingJobs == null || this.dependingJobs.size() == 0) { this.state = State.READY; return this.state; } ControlledJob pred = null; int n = this.dependingJobs.size(); for (int i = 0; i < n; i++) { pred = this.dependingJobs.get(i); State s = pred.checkState(); if (s == State.WAITING || s == State.READY || s == State.RUNNING) { break; // a pred is still not completed, continue in WAITING // state } if (s == State.FAILED || s == State.DEPENDENT_FAILED) { this.state = State.DEPENDENT_FAILED; this.message = "depending job " + i + " with jobID " + pred.getJobID() + " failed. " + pred.getMessage(); break; } // pred must be in success state if (i == n - 1) { this.state = State.READY; } } return this.state; } /** * Submit this job to mapred. The state becomes RUNNING if submission * is successful, FAILED otherwise. */ protected synchronized void submit() { try { Configuration conf = job.getConfiguration(); if (conf.getBoolean(CREATE_DIR, false)) { FileSystem fs = FileSystem.get(conf); Path inputPaths[] = FileInputFormat.getInputPaths(job); for (int i = 0; i < inputPaths.length; i++) { if (!fs.exists(inputPaths[i])) { try { fs.mkdirs(inputPaths[i]); } catch (IOException e) { } } } } job.submit(); this.state = State.RUNNING; } catch (Exception ioe) { LOG.info(getJobName() + " got an error while submitting ", ioe); this.state = State.FAILED; this.message = StringUtils.stringifyException(ioe); } } }