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  1. Core Server
  2. SERVER-17037

output of "top" command is zero on secondary running WT

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Details

    • Bug
    • Status: Closed
    • Critical - P2
    • Resolution: Fixed
    • 3.0.0-rc6
    • 3.0.0-rc7
    • Diagnostics
    • None
    • Fully Compatible
    • ALL

    Description

      first start a replset running wiredtiger

      var x = new ReplSetTest({nodes:3})
      x.startSet({storageEngine:"wiredTiger"})
      x.initiate()

      then put some load on the primary

      while (1) { x.getPrimary().getDB('test').test.insert({}); }

      compare the output of the top command on the primary and the secondary. the total time on the namespace being written to increases on the primary, but never changes on the secondary.

      testReplSet:PRIMARY> before=db.runCommand("top").totals["test.test"].total.time; sleep(1000); after=db.runCommand("top").totals["test.test"].total.time;print(after-before)
      170816
       
      ...
       
      testReplSet:SECONDARY> before=db.runCommand("top").totals["test.test"].total.time; sleep(1000); after=db.runCommand("top").totals["test.test"].total.time;print(after-before)
      0

      it does behave correctly if you use mmapv1 instead though:

      testReplSet:PRIMARY> before=db.runCommand("top").totals["test.test"].total.time; sleep(1000); after=db.runCommand("top").totals["test.test"].total.time;print(after-before)
      135118
      ...
      testReplSet:SECONDARY> before=db.runCommand("top").totals["test.test"].total.time; sleep(1000); after=db.runCommand("top").totals["test.test"].total.time;print(after-before)
      75982

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            kaloian.manassiev@mongodb.com Kaloian Manassiev
            mikeo@mongodb.com Michael O'Brien
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            Dates

              Created:
              Updated:
              Resolved: