Sandy Ryza created YARN-499:
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Summary: On failure, include last n lines of container logs in
diagnostics
Key: YARN-499
URL: https://issues.apache.org/jira/browse/YARN-499
Project: Hadoop YARN
Issue Type: Improvement
Components: nodemanager
Affects Versions: 2.0.3-alpha
Reporter: Sandy Ryza
Assignee: Sandy Ryza
When a container fails, the only way to diagnose it is to look at the logs.
ContainerStatuses include a diagnostic string that is reported back to the
resource manager by the node manager.
Currently in MR2 I believe whatever is sent to the task's standard out is added
to the diagnostics string, but for MR standard out is redirected to a file
called stdout. In MR1, this string was populated with the last few lines of
the task's stdout file, and got printed to the console, allowing for easy
debugging.
Handling this would help to soothe the infuriating problem of an AM dying for a
mysterious reason before setting a tracking URL (MAPREDUCE-3688).
This could be done in one of two ways.
* Use tee to send MR's standard out to both the stdout file and standard out.
This requires modifying ShellCmdExecutor to roll what it reads in, as we
wouldn't want to be storing the entire task log in NM memory.
* Read the task's log files. This would require standardizing or making the
container log files configurable. Right now the log files are determined in
userland and all that is YARN is aware of the log directory.
Does this present any issues I'm not considering? If so it this might only be
needed for AMs?
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