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  1. Core Server
  2. SERVER-55035

Mongo Write Lock shows 100 %, even there are no write operations shown in mongostat output

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    • Bug
    • Status: Closed
    • Major - P3
    • Resolution: Done
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    Description

      mongostats shows 100 % write lock during some specific period. However, during the same period mongotop shows zero write operations on a mongo cluster. 

      Could you please clarify how mongostat shows 100 % write lock (lrw column) when there is no write operations seen in mongotop output !

       

      System Configuration

      Os Version: CentOS 7
      cat /etc/redhat-release
      CentOS Linux release 7.6.1810 (Core)
      Mongo Version : 3.4.16
      Storage Engine: mmapV1
      Storage Type: Data Path in tmpfs

      [sessionmgr05] out: run: df -hP -x iso9660
      [sessionmgr05] out: Filesystem Size Used Avail Use% Mounted on
      [sessionmgr05] out: /dev/sda2 95G 19G 71G 22% /
      [sessionmgr05] out: devtmpfs 50G 0 50G 0% /dev
      [sessionmgr05] out: tmpfs 50G 28K 50G 1% /dev/shm
      [sessionmgr05] out: tmpfs 50G 2.1G 48G 5% /run
      [sessionmgr05] out: tmpfs 50G 0 50G 0% /sys/fs/cgroup
      [sessionmgr05] out: tmpfs 59G 0 59G 0% /var/data/sessions.1
      [sessionmgr05] out: tmpfs 9.9G 0 9.9G 0% /run/user/0

       

      Attached mongotop, mongostat outputs  for 100 % write lock periods.

       

       

       

       

      Attachments

        1. mongostat.png
          mongostat.png
          69 kB
        2. mongotop.pdf
          260 kB
        3. Write_lock_Graph.png
          Write_lock_Graph.png
          87 kB

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            backlog-server-triage Backlog - Triage Team
            kokilasoumi@gmail.com Kokila Soumi
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              Created:
              Updated:
              Resolved: