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https://issues.apache.org/jira/browse/MAPREDUCE-679?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12749048#action_12749048
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Chris Douglas commented on MAPREDUCE-679:
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bq. Chris, to what API are you referring?
o.a.h.metrics and o.a.h.mapred.JobTrackerInstrumentation
(JobTrackerMetricsInst). Ganglia, Chukwa, etc. push metrics through this
interface. Adding a new interface isn't a small change. For example, the
current patch calls {{JobTracker::runningJobs}} rather than
{{JobTracker::getRunningJobs}}; the former is unsynchronized and accesses
shared data structures. There have been similar issues caused by metrics
frameworks attempting to pull information out of the JobTracker without an
audit of the (regrettable) lock hierarchy. If this receives its data through
the metrics API, then neither you nor maintainers need to consider how this
servlet affects the shared JT data.
bq. No API reports job history in a universally-readable manner (e.g., REST +
XML).
That's fair. Again, I like machine-readable formats and wouldn't object to this
even if it were an interim solution, but I want to be clear about how it gets
its data and what it supports, since we'll be committing ourselves to
maintaining both.
Would JobHistory be a better home for this? Much of the data are not currently
available in the web UI, let alone in a reasonable format.
> XML-based metrics as JSP servlet for JobTracker
> -----------------------------------------------
>
> Key: MAPREDUCE-679
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-679
> Project: Hadoop Map/Reduce
> Issue Type: New Feature
> Components: jobtracker
> Reporter: Aaron Kimball
> Assignee: Aaron Kimball
> Attachments: example-jobtracker-completed-job.xml,
> example-jobtracker-running-job.xml, MAPREDUCE-679.2.patch,
> MAPREDUCE-679.3.patch, MAPREDUCE-679.4.patch, MAPREDUCE-679.patch
>
>
> In HADOOP-4559, a general REST API for reporting metrics was proposed but
> work seems to have stalled. In the interim, we have a simple XML translation
> of the existing JobTracker status page which provides the same metrics
> (including the tables of running/completed/failed jobs) as the human-readable
> page. This is a relatively lightweight addition to provide some
> machine-understandable metrics reporting.
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