[GitHub] tysonnorris opened a new issue #2859: LoadBalancerService does not consider concurrent requests when scheduling

[gi...@git.apache.org]

tysonnorris opened a new issue #2859: LoadBalancerService does not consider concurrent requests when scheduling
URL: https://github.com/apache/incubator-openwhisk/issues/2859
 
 
   Under concurrent requests to controller, LoadBalancerService will not consider concurrent requests when scheduling to an invoker. 
   
   For example, consider `LoadBalacnerServiceObjectTests.scala`, with the following test
   ```
     it should "consider load immediately and jump to next invoker when overloaded" in {
       val invokerCount = 10
       val hash = 2
       val targetInvoker = hash % invokerCount
   
       val invs = invokers(invokerCount).updated(targetInvoker, (InstanceId(targetInvoker), Healthy, 0))
       val step = hashInto(LoadBalancerService.pairwiseCoprimeNumbersUntil(invokerCount), hash)
   
       LoadBalancerService.schedule(invs, 1, hash) shouldBe Some(InstanceId((hash + 0) % invs.size))
       LoadBalancerService.schedule(invs, 1, hash) shouldBe Some(InstanceId((hash + 1) % invs.size))
   
     }
   ```
   
   We have:
   * set the existing load to 0 to start with
   * set the invokerBusyThreshold to 1 on `scheduler()` invocations
   * schedule one activation with hash=2
   * schedule second activation with hash=2
   
   In this case, but activations are scheduled to InstanceId(2), but the second should be scheduled to next invoker since busy threshold is exceeded.
   
   I believe this is related to the changing of `LoadbalancerData.activationCountPerInvoker()` from sync to async. Since LoadBalancerService is processed with multiple threads, the updates to the LoadBalancerData are not seen immediately by other threads.
   
 
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