src/mapred/org/apache/hadoop/mapred/JobID.java

/**
 * 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.DataInput;
import java.io.DataOutput;
import java.io.IOException;
import java.text.NumberFormat;

import org.apache.hadoop.io.Text;

/**
 * JobID represents the immutable and unique identifier for 
 * the job. JobID consists of two parts. First part 
 * represents the jobtracker identifier, so that jobID to jobtracker map 
 * is defined. For cluster setup this string is the jobtracker 
 * start time, for local setting, it is "local".
 * Second part of the JobID is the job number. <br> 
 * An example JobID is : 
 * <code>job_200707121733_0003</code> , which represents the third job 
 * running at the jobtracker started at <code>200707121733</code>. 
 * <p>
 * Applications should never construct or parse JobID strings, but rather 
 * use appropriate constructors or {@link #forName(String)} method. 
 * 
 * @see TaskID
 * @see TaskAttemptID
 * @see JobTracker#getNewJobId()
 * @see JobTracker#getStartTime()
 */
public class JobID extends ID {
  private static final String JOB = "job";
  private String jtIdentifier;
  private static char UNDERSCORE = '_';
  
  private static NumberFormat idFormat = NumberFormat.getInstance();
  static {
    idFormat.setGroupingUsed(false);
    idFormat.setMinimumIntegerDigits(4);
  }
  
  /**
   * Constructs a JobID object 
   * @param jtIdentifier jobTracker identifier
   * @param id job number
   */
  public JobID(String jtIdentifier, int id) {
    super(id);
    this.jtIdentifier = jtIdentifier;
  }
  
  private JobID() { }
  
  public String getJtIdentifier() {
    return jtIdentifier;
  }
  
  @Override
  public boolean equals(Object o) {
    if(o == null)
      return false;
    if(o.getClass().equals(JobID.class)) {
      JobID that = (JobID)o;
      return this.id==that.id
        && this.jtIdentifier.equals(that.jtIdentifier);
    }
    else return false;
  }
  
  /**Compare JobIds by first jtIdentifiers, then by job numbers*/
  @Override
  public int compareTo(ID o) {
    JobID that = (JobID)o;
    int jtComp = this.jtIdentifier.compareTo(that.jtIdentifier);
    if(jtComp == 0) {
      return this.id - that.id;
    }
    else return jtComp;
  }
  
  @Override
  public String toString() {
    StringBuilder builder = new StringBuilder();
    return builder.append(JOB).append(UNDERSCORE)
      .append(toStringWOPrefix()).toString();
  }
  
  /** Returns the string representation w/o prefix */
  StringBuilder toStringWOPrefix() {
    StringBuilder builder = new StringBuilder();
    builder.append(jtIdentifier).append(UNDERSCORE)
    .append(idFormat.format(id)).toString();
    return builder;
  }
  
  @Override
  public int hashCode() {
    return toStringWOPrefix().toString().hashCode();
  }
  
  @Override
  public void readFields(DataInput in) throws IOException {
    super.readFields(in);
    this.jtIdentifier = Text.readString(in);
  }

  @Override
  public void write(DataOutput out) throws IOException {
    super.write(out);
    Text.writeString(out, jtIdentifier);
  }
  
  public static JobID read(DataInput in) throws IOException {
    JobID jobId = new JobID();
    jobId.readFields(in);
    return jobId;
  }
  
  /** Construct a JobId object from given string 
   * @return constructed JobId object or null if the given String is null
   * @throws IllegalArgumentException if the given string is malformed
   */
  public static JobID forName(String str) throws IllegalArgumentException {
    if(str == null)
      return null;
    try {
      String[] parts = str.split("_");
      if(parts.length == 3) {
        if(parts[0].equals(JOB)) {
          return new JobID(parts[1], Integer.parseInt(parts[2]));
        }
      }
    }catch (Exception ex) {//fall below
    }
    throw new IllegalArgumentException("JobId string : " + str 
        + " is not properly formed");
  }
  
  /** 
   * Returns a regex pattern which matches task IDs. Arguments can 
   * be given null, in which case that part of the regex will be generic.  
   * For example to obtain a regex matching <i>any job</i> 
   * run on the jobtracker started at <i>200707121733</i>, we would use :
   * <pre> 
   * JobID.getTaskIDsPattern("200707121733", null);
   * </pre>
   * which will return :
   * <pre> "job_200707121733_[0-9]*" </pre> 
   * @param jtIdentifier jobTracker identifier, or null
   * @param jobId job number, or null
   * @return a regex pattern matching JobIDs
   */
  public static String getJobIDsPattern(String jtIdentifier, Integer jobId) {
    StringBuilder builder = new StringBuilder(JOB).append(UNDERSCORE);
    builder.append(getJobIDsPatternWOPrefix(jtIdentifier, jobId));
    return builder.toString();
  }
  
  static StringBuilder getJobIDsPatternWOPrefix(String jtIdentifier
      , Integer jobId) {
    StringBuilder builder = new StringBuilder()
      .append(jtIdentifier != null ? jtIdentifier : "[^_]*").append(UNDERSCORE)
      .append(jobId != null ? idFormat.format(jobId) : "[0-9]*");
    return builder;
  }
  
}