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  1. Core Server
  2. SERVER-42256

Mongo unable to evict cache

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Details

    • Bug
    • Status: Closed
    • Major - P3
    • Resolution: Gone away
    • 3.4.16
    • None
    • None
    • ALL

    Description

      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.

      Attachments

        1. eviction_server.png
          eviction_server.png
          372 kB
        2. screenshot-1.png
          screenshot-1.png
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        3. screenshot-2.png
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        4. Screenshot from 2019-07-17 14-12-00.png
          Screenshot from 2019-07-17 14-12-00.png
          35 kB
        5. Screenshot from 2019-07-17 14-42-58.png
          Screenshot from 2019-07-17 14-42-58.png
          17 kB
        6. Screenshot from 2019-07-18 17-27-37.png
          Screenshot from 2019-07-18 17-27-37.png
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        7. workload_shift.png
          workload_shift.png
          196 kB

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              edwin.zhou@mongodb.com Edwin Zhou
              spuyet@gmail.com Sébastien Puyet
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              Dates

                Created:
                Updated:
                Resolved: