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https://issues.apache.org/jira/browse/STORM-886?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14715347#comment-14715347
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ASF GitHub Bot commented on STORM-886:
--------------------------------------
Github user revans2 commented on a diff in the pull request:
https://github.com/apache/storm/pull/700#discussion_r38021586
--- Diff: storm-core/src/clj/backtype/storm/daemon/executor.clj ---
@@ -602,7 +607,15 @@
(log-message "Activating spout " component-id ":"
(keys task-datas))
(fast-list-iter [^ISpout spout spouts] (.activate
spout)))
- (fast-list-iter [^ISpout spout spouts] (.nextTuple
spout)))
+ (if (and
+ ((:storm-conf executor-data)
TOPOLOGY-BACKPRESSURE-ENABLE)
+ @(:throttle-on (:worker executor-data))
+ suspend-time
+ (not= suspend-time 0))
+ (do
--- End diff --
Can we move this conditional up to be part of the
overflow-buffer/max-spout-pending check? It feels like it fits better there,
and that we don't want to output anything when back-pressure is on, instead of
just slowing down how quickly we output.
Also instead of logging something, can we look at having a metric instead
that shows how may times we called paused for a given reason. Logging is not
going to really give us the picture we want and is going to be difficult to
follow.
> 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
> Attachments: an simple example for backpressure.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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