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  1. MongoDB Database Tools
  2. TOOLS-3832

Investigate changes in WT-11171: Add metrics that give better insight into what checkpoint is doing

    • Type: Icon: Investigation Investigation
    • Resolution: Won't Do
    • Priority: Icon: Major - P3 Major - P3
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    • Affects Version/s: None
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    • Tools and Replicator

      Original Downstream Change Summary

      Checkpoint statistics were altered:

      • Checkpoint-related stats got moved out of the big "transaction" category into their own "checkpoint" category
      • The descriptions were altered to remove the redundant "transaction checkpoint" text (since them being in the checkpoint category already adds the "checkpoint" text to the description automatically)
      • "checkpoint running" became "checkpoint state", and works largely the same except that any non-zero value is equivalent to the old "1" value.
      • "checkpoint currently running for history store file" got folded into the checkpoint state and is no longer a separate statistic

        Description of Linked Ticket

        Checkpointing is one of the most user-visibly disruptive maintenance operations WiredTiger does. Sometimes a lot of time is spent doing checkpoints, and it isn't clear what it is doing with that time.

      We should add metrics and/or log lines that give better insight.

      An example from a customer shows checkpoints completing in between 15 and 20 minutes, spending 4 minutes of that time writing content (2 at the start, 2 at the end), with no meaningful indication of what happens for the remaining 11 to 16 minutes. There is no meaningful time being spent flushing checkpoint content to disk.

      A starting point for this is probably building or finding a workload that takes a long time to create a new checkpoint.

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            Reporter:
            backlog-server-pm Backlog - Core Eng Program Management Team
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