Github user revans2 commented on a diff in the pull request:
https://github.com/apache/storm/pull/700#discussion_r38023281
--- Diff: storm-core/src/clj/backtype/storm/daemon/worker.clj ---
@@ -114,12 +114,34 @@
(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)]
+ (if executors
+ (if (reduce #(or %1 %2) (map #(.get-backpressure-flag %1)
executors))
+ (reset! (:backpressure worker) true) ;; at least one
executor has set backpressure
+ (reset! (:backpressure worker) false))) ;; no executor has
backpressure set
+ ;; update the worker's backpressure flag to zookeeper here
+ (.worker-backpressure! storm-cluster-state storm-id assignment-id
port @(:backpressure worker))
--- End diff --
I think we have an opportunity here to not put so much load on ZK. We
should be able to keep cached if we think back-pressure is on or not for this
worker, and only update if we think it is changing, instead of reading the
state each time and updating it, if it is different. This is being called at
least ever 100 ms, which is going to put more load on ZK then I like.
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