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  1. Jenkins
  2. JENKINS-58101

jenkins slowdown with many offline nodes

    Details

    • Type: Bug
    • Status: Open (View Workflow)
    • Priority: Minor
    • Resolution: Unresolved
    • Component/s: core
    • Labels:
      None
    • Environment:
      linux java8 x64,
      jenkins 2.176.1,
      workflow-durable-task-step 2.30
    • Similar Issues:

      Description

      Having a large number of offline executors causes massive slowdown in  hudson.model.Queue. The maintain method is holding the queue lock over 80% of the time in some cases.

      "AtmostOneTaskExecutor[Periodic Jenkins queue maintenance] 
         java.lang.Thread.State: RUNNABLE
              at org.jenkinsci.plugins.durabletask.executors.ContinuedTask$Scheduler.canTake(ContinuedTask.java:66)
              at hudson.model.Queue$JobOffer.getCauseOfBlockage(Queue.java:278)
              at hudson.model.Queue.maintain(Queue.java:1616)
              at hudson.model.Queue$1.call(Queue.java:325)
              at hudson.model.Queue$1.call(Queue.java:322)
      

      Steps to reproduce:

      1. install jenkins + job-dsl-plugin + matrix-project-plugin + ssh-slaves-plugin + workflow-durable-task-step (Pipeline: nodes and processes)
      2. create a ssh node with 500 executors, add some random labels "a b c d e f g h i"
      3. mark the node offline using configure->availability->"bring online according to schedule"
      4. create the jobs using job dsl below
      5. wait for the jobs to start, observe the sluggish queue, fire up jvisualvm to analyze
      configs = []
      for (int i = 0; i < 100; i++) {
        configs.add(String.valueOf(i))
      }
      
      for (int i = 0; i < 10; i++) {
        matrixJob("matrix-"+i) {
          axes {
            text('cfg', configs)
          }
          triggers {
            cron('* * * * *')
          }
          steps {
            shell('sleep 30')
          }
        }
      }
      

      It seems each "parked executor" causes a Queue$JobOffer to be created, which is turn triggers some getCauseOfBlockage analysis. This seems to do blockedItems * buildableItems operations which can get quite slow for a large job queue.

      How it was found: We have ~80 nodes with 10 executors each. We took half of them offline during a hardware migration. Soon our jobs filled the queue with 2000 items. Jenkins started timing out due to queue lock contention - a single maintain() call took around 60sec.

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              • Assignee:
                Unassigned
                Reporter:
                mbakhoff Märt Bakhoff
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                Dates

                • Created:
                  Updated: