Is it possible to restart a "killed" Hadoop job from where it left off?

Question

I have a Hadoop job that processes log files and reports some statistics. This job died about halfway through the job because it ran out of file handles. I have fixed the issue with the file handles and am wondering if it is possible to restart a "killed" job.

Answer 1

As it turns out, there is not a good way to do this; once a job has been killed there is no way to re-instantiate that job and re-start processing immediately prior to the first failure. There are likely some really good reasons for this but I'm not qualified to speak to this issue.

In my own case, I was processing a large set of log files and loading these files into an index. Additionally I was creating a report on the contents of these files at the same time. In order to make the job more tolerant of failures on the indexing side (a side-effect, this isn't related to Hadoop at all) I altered my job to instead create many smaller jobs, each one of these jobs processing a chunk of these log files. When one of these jobs finishes, it renames the processed log files so that they are not processed again. Each job waits for the previous job to complete before running.

• Chaining multiple MapReduce jobs in Hadoop

When one job fails, all of the subsequent jobs quickly fail afterward. Simply fixing whatever the issue was and the re-submitting my job will, roughly, pick up processing where it left off. In the worst-case scenario where a job was 99% complete at the time of it's failure, that one job will be erroneously and wastefully re-processed.