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https://issues.apache.org/jira/browse/STORM-886?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14725635#comment-14725635
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ASF GitHub Bot commented on STORM-886:
--------------------------------------
Github user zhuoliu commented on a diff in the pull request:
https://github.com/apache/storm/pull/700#discussion_r38438290
--- Diff: storm-core/src/clj/backtype/storm/daemon/worker.clj ---
@@ -114,12 +114,38 @@
(fast-list-iter [[task tuple :as pair] tuple-batch]
(.serialize serializer tuple)))
+(defn- mk-backpressure-handler [executors]
+ "make a handler that checks and updates worker's backpressure flag"
+ (disruptor/backpressure-handler
+ (fn [worker]
+ (let [storm-id (:storm-id worker)
+ assignment-id (:assignment-id worker)
+ port (:port worker)
+ storm-cluster-state (:storm-cluster-state worker)
+ prev-backpressure-flag @(:backpressure worker)]
+ (doseq [ed executors] ;; Debug, TODO: delete
+ (log-message "zliu executor" (.get-executor-id ed) " flag is "
(.get-backpressure-flag ed)))
--- End diff --
Thanks for the reminder, I will remove all those debug messages soon after
the unit test commit.
> 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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