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  1. Core Server
  2. SERVER-22274

WiredTiger cache size is only configurable in whole gigabytes.

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Details

    • Bug
    • Status: Closed
    • Minor - P4
    • Resolution: Cannot Reproduce
    • 3.0.8
    • None
    • WiredTiger
    • None
    • ALL

    Description

      Hello, on our development servers we currently run our application server alongside a standalone mongod instance. Ever since WiredTiger was introduced we have the occasional OOM killer issue where app server RAM + WT cache + file system buffers are way higher than these smaller instances have.

      I was looking into overriding the WT cache size into something smaller and found this option:
      https://docs.mongodb.org/manual/reference/configuration-options/#storage.wiredTiger.engineConfig.cacheSizeGB

      The problem is that this only allows this value to be specified in whole gigabytes while total RAM of these instances is only 1 or 2 Gb. Specifying this value as a fraction results in parse errors as this field is parsed as an integer. I also tried other key names such as 'cacheSizeMB' or 'cacheSize' without any luck. I also tried using a letter as in indicator ('200M') but that leads to another parsing error.

      I found a workaround in this post but that does not seem to work (anymore?):
      https://groups.google.com/forum/#!topic/mongodb-user/GLrp-H31YWg

      Are there plans to specify this value in a more specific way. Also, is there a current workaround for this?

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              kelsey.schubert@mongodb.com Kelsey T Schubert
              jeroenv Jeroen Vijfhuizen
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