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  1. Core Server
  2. SERVER-57230

mongos doesn't distribute secondary reads evenly on v4.4 or above

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    Details

    • Type: Bug
    • Status: In Progress
    • Priority: Major - P3
    • Resolution: Unresolved
    • Affects Version/s: 4.4.0
    • Fix Version/s: 5.1 Required
    • Component/s: None
    • Operating System:
      ALL
    • Sprint:
      Service Arch 2021-06-28, Service Arch 2021-07-12, Service Arch 2021-08-09, Service Arch 2021-08-23, Service Arch 2021-10-04
    • Story Points:
      5

      Description

      In v4.2, mongos correctly balanced outgoing read requests to secondary nodes by randomizing the connection order when we issued requests here. In v4.4, the introduction of either hedged reads, opportunistic reads, or changes to ConnectionPool have made it such that one of these connections now consistently resolves first, effectively starving one of the secondaries of any reads and unbalancing our read requests. In this ticket, create a unit or integration test to capture this behavior and fix it.

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            Assignee:
            tyler.seip Tyler Seip
            Reporter:
            tyler.seip Tyler Seip
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              Dates

              Created:
              Updated: