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https://issues.apache.org/jira/browse/YARN-5269?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15904194#comment-15904194
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Joep Rottinghuis commented on YARN-5269:
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After looking at the code I am indeed a little surprised that we're not
properly doing this.
All the plumbing seems correct on the client side:
TimelineV2ClientImpl#putEntities vs TimelineV2ClientImpl#putEntitiesAsync
correctly call TimelineEntityDispatcher#dispatchEntities(boolean sync,... with
the correct argument. This argument does seem to make it into the params, and
on the server side TimelineCollectorWebService#putEntities correctly pulls the
async parameter from the rest call. See line 156:
{code}
boolean isAsync = async != null && async.trim().equalsIgnoreCase("true");
{code}
However, this is where the problem starts. It simply calls
TimelineCollector#putEntities and ignores the value of isAsync. It should
instead have called TimelineCollector#putEntitiesAsync, which is currently not
implemented.
putEntities should call putEntitiesAsync and then after that call writer.flush()
The fact that we flush on close and we flush periodically should be more of a
concern of avoiding data loss; close in case sync is never called and the
periodic flush to guard against having data from slow writers get buffered for
a long time and expose us to risk of loss in case the collector crashes with
data in its buffers. Size-based flush is a different concern to avoid blowing
up memory footprint.
The spooling behavior is also somewhat separate.
We have two separate methods on our API putEntities and putEntitiesAsync and
they should have different behavior beyond waiting for the request to be sent.
I can file a separate bug from this one dealing with exception handling to
tackle the sync vs async nature. During the meeting today I was thinking about
the HBase writer that has a flush, which definitely blocks until data is
flushed to HBase (ignoring the spooling for the moment).
> Bubble exceptions and errors all the way up the calls, including to clients.
> ----------------------------------------------------------------------------
>
> Key: YARN-5269
> URL: https://issues.apache.org/jira/browse/YARN-5269
> Project: Hadoop YARN
> Issue Type: Sub-task
> Components: timelineserver
> Affects Versions: YARN-2928
> Reporter: Joep Rottinghuis
> Assignee: Haibo Chen
> Labels: YARN-5355, yarn-5355-merge-blocker
>
> Currently we ignore (swallow) exception from the HBase side in many cases
> (reads and writes).
> Also, on the client side, neither TimelineClient#putEntities (the v2 flavor)
> nor the #putEntitiesAsync method return any value.
> For the second drop we may want to consider how we properly bubble up
> exceptions throughout the write and reader call paths and if we want to
> return a response in putEntities and some future kind of result for
> putEntitiesAsync.
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