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  1. Jenkins
  2. JENKINS-47724

Pipeline with parallel jobs performance issue with EC2 slaves



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      We are in the process of converting our freestyle matrix jobs over to parallel pipeline and we are seeing a few performance issues when using pipeline. We are able to reproduce the issue using sample pipeline code that is very similar to -JENKINS-45553-. We are also using the EC2 plugin to start and stop slaves. In all of my testing below, the slaves were started outside of pipeline jobs to prevent slave startup time from skewing any results.

      Parallel Pipeline code:

      def stepsForParallel = [:]
      for (int i = 0; i < 150; i++) {
        def s = "subjob_${i}" 
        stepsForParallel[s] = {
          node("JENKINS-SLAVE-NODE-LABEL") {
            sh '''
            date +%c
      timestamps {
      parallel stepsForParallel

      1. Freestyle Matrix VS Parallel Pipeline

      Using 16 slave VMs:
      I have a freestyle matrix axis job that runs the date command on slaves across 355 slave nodes. This build took 28 seconds to run after slave startup and around 23 seconds thereafter.

      Using the sample parallel pipeline above with 355 branches, it takes 4 mins and 49 seconds to complete after the slaves are started and then around 2 minus 47 seconds thereafter.

      I'm unsure why the time discrepancy is so large when both jobs are performing the same work with the same output.

      2. The first parallel pipeline job on a slave is slower

      I'm noticing that after the 16 slaves are started, the first pipeline job that runs takes a lot longer than subsequent runs. See below.
      First build after slaves started: 4m 49s
      Subsequent runs: 2m 47s, 2m 44s, 2m 43s, 2m 32s
      After Jenkins slaves were stopped and then started without restarting Jenkins
      the parallel pipeline job took 6m 36s to complete.
      With extra debugging I did see this.

      pipeline performance after slave restart

      Slaves started:
      4m 49s
      timings for OwnerJOBNAME/34:JOBNAME #34:
      Unknown macro: {classLoad=79ms, flowNode=29209ms, parse=49ms, run=287301ms, saveProgram=9880ms}
      Build Reran:
      2m 44s
      timings for OwnerJOBNAME/35:JOBNAME #35:
      Unknown macro: {classLoad=8ms, flowNode=34032ms, parse=21ms, run=162601ms, saveProgram=9192ms}
      Slaves restarted:
      5m 4s
      timings for OwnerJOBNAME/36:JOBNAME #36:
      Unknown macro: {classLoad=108ms, flowNode=33247ms, parse=71ms, run=301825ms, saveProgram=8836ms}

      I tried first running a freestyle job and then a parallel pipeline job after slaves were restarted but it didn't help. I'm unsure why there is a performance penalty for being the first pipeline job to run on a slave after it is started.

      3. Parallel pipeline job appears to pause when starting on slaves

      This is a major issue for us. When running a parallel pipeline job, I can see the slaves on the left nav all show part of the pipeline job and an increasing queue. This process appears to hang or pause for a significant large amount of time. I verified on the slaves that they are idle and not doing anything. The Jenkins master shows little CPU and disk I/O load. This issue seems to get worse with an increased slave count.

      Duration Branches Slave VMs
      14m 100 100
      3m 100 16
      1m 13s 100 4
      29m 1000 16
      34m 1000 4

      I would expect to see that parallel pipeline jobs run faster with more slaves not slower. I'm attaching thread dumps that I took during the pause.



      log files during pause period

      In the debug log I see this repeat slowly

      Oct 30, 2017 2:05:30 AM FINEST org.jenkinsci.plugins.workflow.steps.durable_task.DurableTaskStep

      -JENKINS-34021-: DurableTaskStep.Execution.listener present in CpsStepContext[471:sh]:OwnerJOBNAME #83

      In the console log I see the following. Note a 2 minute pause occurs after the first line when watching the console log in real time

      02:05:35 [subjob_149] Waiting for next available executor on JENKINS-SLAVE-LABEL
      02:05:30 [subjob_0] + date +%c
      02:05:39 [subjob_6] + date +%c
      02:05:49 [subjob_5] + date +%c
      02:05:58 [subjob_1] + date +%c
      02:06:07 [subjob_2] + date +%c
      02:06:16 [subjob_4] + date +%c
      02:06:25 [subjob_3] + date +%c
      02:06:34 [subjob_10] + date +%c
      02:06:44 [subjob_7] + date +%c
      02:06:53 [subjob_8] + date +%c
      02:07:02 [subjob_15] + date +%c
      02:07:11 [subjob_12] + date +%c
      02:07:20 [subjob_9] + date +%c
      02:07:29 [subjob_11] + date +%c
      02:07:39 [subjob_13] + date +%c
      02:07:48 [subjob_14] + date +%c




      I ran the sample parallel pipeline code on the Jenkins master and with 100 branches and 100 executors and couldn't reproduce the problem. I also ran the sample pipeline code with ' echo Hello ' instead of ' sh "date +%c" ' and also couldn't reproduce the problem. Adding additional sh commands to run on the slaves didn't add any significant time to the builds. I'm not sure if this issue is specific to EC2 plugin slaves. The slaves were started and fully running before any of the above tests were performed to minimize EC2 plugin involvement.

      Tickets that maybe related:


      4. High CPU on Jenkins Masters

      I'm seeing higher CPU usage on our Jenkins masters that are running parallel pipeline code compared to freestyle.  In addition, the more parallel branches that are ran the higher the load.  I tried to quantify the differences in the table below using a freestyle matrix job and parallel pipeline job that performs close to the same code on 2 CPU / 8 GB RAM sized Jenkins Master instances.


      Type number of
      number of
      slaves agents
      peak 1m
      load avg
      peak 5m
      load avg
      15m load avg
      when job finished
      Freestyle 259 55 2.0 .53 .08
      Pipeline 259 60 3.19 1.7 .85
      Pipeline 259 120 4.38 1.7 .89
      Pipeline 259 190 4.34 2.03 1.06
      Pipeline 355 190 6.26 2.12 .98

      In summary, when using parallel pipeline I'm seeing higher load average on the Jenkins masters as the number of branches and slaves agents increases even though all of the testing occurs on Jenkins slave agents.  Matrix freestyle jobs compared to parallel pipeline seem to have a fraction of the Jenkins master load after the initial peak.

      UPDATE: Running two parallel pipeline jobs with a total of 110 slave agents pushed the Jenkins master instance to a peak 1m load avg of 10.77 and peak 5m load avg to 7.18.





            Unassigned Unassigned
            mkozell Mike Kozell
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