JobTracker Recovery
When JobTracker failover, the new JobTracker takes over from where the first JobTracker left off. Job and task activity persist in the JobTracker volume, so the new JobTracker can resume activity immediately upon launching. The TaskTrackers maintain information about the state of each task, so that when they connect to the new JobTracker they are able to continue without interruption.
By default, JobTracker recovery is enabled and configured to work without further configuration as long as more than one node can run the JobTracker service. However, you can configure the following recovery properties in the Hadoop 1.x mapred-site.xml:
| Property | Description |
|---|---|
| mapreduce.jobtracker.recovery.dir |
Recovery Directory. Default value: /var/mapr/cluster/mapred/jobTracker/recovery |
| mapreduce.jobtracker.recovery.maxtime | Maximum time in seconds JobTracker should stay in recovery mode. Default value: 120 |
| mapred.jobtracker.restart.recover | "true" to enable (job) recovery upon restart, "false" to start afresh Default value: true |
| mapreduce.jobtracker.recovery.job.initialization.maxtime | This property's value specifies the maximum time in seconds that the JobTracker waits to initialize jobs before starting recovery. This property's default value is equal to the value of the mapreduce.jobtracker.recovery.maxtime property. Default value: 480 |
NOTE:
When changing any of the JobTracker
recovery parameters, a JobTracker restart is required.