[jira] [Commented] (STORM-886) Automatic Back Pressure

["ASF GitHub Bot (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/STORM-886?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14725620#comment-14725620 ] 

ASF GitHub Bot commented on STORM-886:
--------------------------------------

Github user redsanket commented on a diff in the pull request:

    https://github.com/apache/storm/pull/700#discussion_r38437006
  
    --- 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 --
    
    zliu in log message


> 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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