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  1. Core Server
  2. SERVER-23892

Do periodic replicated writes every 10 seconds while idle (for maxStalenessMS)

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Details

    • New Feature
    • Status: Closed
    • Major - P3
    • Resolution: Fixed
    • None
    • 3.3.12
    • Replication
    • None
    • Fully Compatible
    • Sharding 18 (08/05/16), Sharding 2016-08-29, Sharding 2016-09-19
    • 0

    Description

      For the upcoming maxStalenessMS read preference it is required that periodically there needs to be a replicated write - so it would have a new oplog entry to move forward the OpTime reported to clients.

      These no-op 'n' writes should only be done on the primary when no other replicated writes have been done in the timeout period.

      A side-effect of this will be that an idle replica set will no longer be idle with respect to writes, since it will internally force a write periodically. This new behavior (which also exists in master-slave replication) will show up in things like the calculation of "replication lag" never exceeding a second or two on caught up nodes – previously a lack of writes for a few minutes would immediately show a lag of that period as the new write comes in until it is replicated.

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              misha.tyulenev@mongodb.com Misha Tyulenev
              jesse@mongodb.com A. Jesse Jiryu Davis
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                Created:
                Updated:
                Resolved: