[GitHub] markusthoemmes commented on a change in pull request #4137: Remove busy loop in case the invoker is overloaded.

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markusthoemmes commented on a change in pull request #4137: Remove busy loop in case the invoker is overloaded.
URL: https://github.com/apache/incubator-openwhisk/pull/4137#discussion_r237025725
 
 

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 File path: core/invoker/src/main/scala/org/apache/openwhisk/core/containerpool/ContainerPool.scala
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 @@ -99,13 +99,16 @@ class ContainerPool(childFactory: ActorRefFactory => ActorRef,
     // their requests and send them back to the pool for rescheduling (this may happen if "docker" operations
     // fail for example, or a container has aged and was destroying itself when a new request was assigned)
     case r: Run =>
-      // Check if the message is resent from the buffer. Only the first message on the buffer can be resent.
-      val isResentFromBuffer = runBuffer.nonEmpty && runBuffer.dequeueOption.exists(_._1.msg == r.msg)
+      // Checks if the current message is the first in the queue
+      val isFirstInQueue = runBuffer.dequeueOption.exists(_._1.msg == r.msg)
+      // A resend is only valid, if the message is the first one in the queue. Otherwise it is a result of a race condition.
+      val isValidResent = r.fromQueue && isFirstInQueue
 
 Review comment:
   Since you already switched to using a `runFirstMessageOfQueue` method, can we simplify our logic towards this:
   
   1. On getting a run message, we always append to the buffer
   2. After appending, we'll run the `runFirstMessageOfQueue` method
   
   I imagine that that way, we don't need the `isFirstInQueue` and `isValidResent` checks, as that guarantees that we always send messages off of a queue.
   
   (The `Run` handler could of course optimize, and bypass the queue if it knows it's empty)
   
   WDYT?

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