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https://issues.apache.org/jira/browse/MAPREDUCE-1881?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12896769#action_12896769
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Matei Zaharia commented on MAPREDUCE-1881:
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Sure, I can do that. I think the biggest risk with the composite object is
adding a method to TaskTrackerInstrumentation that we forget to add in the
composite. While this is bad, it would arguably get noticed faster if the
composite object is used by default than if it isn't. Any other opinions on
this? Any other reasons to avoid it?
I really see the composite object as not much different than having a for loop
at every call site. Supporting multiple instrumentation objects is clearly
useful (the same way that most classes in the JDK with events support multiple
listeners). The question then is how to do it. Since the instrumentation
interface isn't designed in such a way that an implementation knows who called
it (i.e. can tell whether it went through a composite object), it seems OK to
use a composite object to route calls to a list of implementations.
> Improve TaskTrackerInstrumentation
> ----------------------------------
>
> Key: MAPREDUCE-1881
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-1881
> Project: Hadoop Map/Reduce
> Issue Type: Improvement
> Reporter: Matei Zaharia
> Assignee: Matei Zaharia
> Priority: Minor
> Attachments: mapreduce-1881-v2.patch, mapreduce-1881.patch
>
>
> The TaskTrackerInstrumentation class provides a useful way to capture key
> events at the TaskTracker for use in various reporting tools, but it is
> currently rather limited, because only one TaskTrackerInstrumentation can be
> added to a given TaskTracker and this objects receives minimal information
> about tasks (only their IDs). I propose enhancing the functionality through
> two changes:
> # Support a comma-separated list of TaskTrackerInstrumentation classes rather
> than just a single one in the JobConf, and report events to all of them.
> # Make the reportTaskLaunch and reportTaskEnd methods in
> TaskTrackerInstrumentation receive a reference to a whole Task object rather
> than just its TaskAttemptID. It might also be useful to make the latter
> receive the task's final state, i.e. failed, killed, or successful.
> I'm just posting this here to get a sense of whether this is a good idea. If
> people think it's okay, I will make a patch against trunk that implements
> these changes.
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