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  1. Core Server
  2. SERVER-42343

WiredTigerLAS.wt grows when lagged node is in maintenance mode

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    Details

    • Type: Bug
    • Status: Closed
    • Priority: Major - P3
    • Resolution: Fixed
    • Affects Version/s: 3.4.20
    • Fix Version/s: 3.4.23
    • Component/s: None
    • Labels:
      None
    • Backwards Compatibility:
      Fully Compatible
    • Operating System:
      ALL
    • Sprint:
      Execution Team 2019-07-29, Execution Team 2019-08-12, Execution Team 2019-08-26

      Description

      As part of rolling index builds and similar operations, we'll often take nodes offline for O(hours). When the node comes back online, we'll put it into maintenance mode (using replSetMaintenance) until the node catches back up. We've observed that such nodes often end up with a huge WiredTigerLAS.wt file. We've done some investigation and it seems to be the case that this only happens when we put the node into maintenance mode; if we simply let a lagged node stay in secondary mode, we don't see WiredTigerLAS.wt grow.

      We suspect this is related to cache pressure of majority read concern since we only started seeing these issues when we enabled that.

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                  Updated:
                  Resolved: