Major Description
Some jobs (like Sqoop or HBase jobs) are not idempotent, so should not be recovered on jobtracker restart. MAPREDUCE-2702 solves this problem for MR2, however the approach there is not applicable for MR1, since even if we only use the job-level part of the patch and add a isRecoverySupported method to OutputCommitter, there is no way to use that information from the JT (which initiates recovery), since the JT does not instantiate OutputCommitters - and it shouldn't since they are user-level code. (In MR2 it's OK since the MR AM calls the method.)
Instead, we can add a MR configuration property to say that a job is not recoverable, and the JT could safely read this from the job conf.