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  1. Core Server
  2. SERVER-42256

Mongo unable to evict cache



    • Type: Bug
    • Status: Waiting For User Input
    • Priority: Major - P3
    • Resolution: Unresolved
    • Affects Version/s: 3.4.16
    • Fix Version/s: None
    • Labels:
    • Operating System:


      Yesterday, we had multiple slowdown on our primary server:

      From our metrics, we can see that the cache evictions threads were not able to evict cache fast enough until the cache used reached 95% and that applications threads started to help the dedicated threads (source: http://source.wiredtiger.com/mongodb-3.4/tune_cache.html):

      We already encountered this issue with mongo 3.2 two years ago (on the secondary server though) and the only thing that fixed the issue was to upgrade to mongo 3.4: https://jira.mongodb.org/browse/SERVER-27700

      We plan to upgrade to mongo 3.6 in the following months but can you check that a regression has not be introduced in our current mongo version ?

      Another related ticket: https://jira.mongodb.org/browse/SERVER-27753

      I can provide you diagnostic.data and slow log files. Thx for you help.


        1. eviction_server.png
          372 kB
          Dmitry Agranat
        2. screenshot-1.png
          103 kB
          Adrien Jarthon
        3. screenshot-2.png
          105 kB
          Adrien Jarthon
        4. Screenshot from 2019-07-17 14-12-00.png
          35 kB
          Sébastien Puyet
        5. Screenshot from 2019-07-17 14-42-58.png
          17 kB
          Sébastien Puyet
        6. Screenshot from 2019-07-18 17-27-37.png
          41 kB
          Sébastien Puyet
        7. workload_shift.png
          196 kB
          Dmitry Agranat



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