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https://issues.apache.org/jira/browse/STORM-886?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14939711#comment-14939711
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ASF GitHub Bot commented on STORM-886:
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Github user rsltrifork commented on the pull request:
https://github.com/apache/storm/pull/700#issuecomment-144703338
Does this solve the problem of tuple timeout, when a bolt is completely
stalled waiting for an external component to get back up?
I believe waiting for too long in a bolt triggers the tuple timeout, which
causes the Spout to reemit, which is usually not what we want, when a bolt is
waiting in a controlled manner before it can resume computation.
Ideally, the tuple timeout should be used as a last resort to detect that
internal storm components don't respond. And back pressure should ensure that
the Spout doesn't reemit to temporarily busy/blocked bolts - regardless of
timeout.
> Automatic Back Pressure
> -----------------------
>
> Key: STORM-886
> URL: https://issues.apache.org/jira/browse/STORM-886
> Project: Apache Storm
> Issue Type: Improvement
> Reporter: Robert Joseph Evans
> Assignee: Zhuo Liu
> Fix For: 0.11.0
>
> Attachments: aSimpleExampleOfBackpressure.png, backpressure.png
>
>
> This new feature is aimed for automatic flow control through the topology DAG
> since different components may have unmatched tuple processing speed.
> Currently, the tuples may get dropped if the downstream components can not
> process as quickly, thereby causing a waste of network bandwidth and
> processing capability. In addition, it is difficult to tune the
> max.spout.pending parameter for best backpressure performance. Therefore, an
> automatic back pressure scheme is highly desirable.
> Heron proposed a form of back pressure that does not rely on acking or max
> spout pending. Instead spouts throttle not only when max.spout.pending is
> hit, but also if any bolt has gone over a high water mark in their input
> queue, and has not yet gone below a low water mark again. There is a lot of
> room for potential improvement here around control theory and having spouts
> only respond to downstream bolts backing up, but a simple bang-bang
> controller like this is a great start.
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