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  1. Core Server
  2. SERVER-30460

Grow the oplog when the replication commit point falls behind the back of where it would normally be truncated to

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    • Fully Compatible
    • Repl 2018-11-19, Repl 2018-12-03, Repl 2018-12-17, Repl 2019-01-14

    Description

      If the replication majority commit point is far enough behind the primary that the oplog entry on the primary that corresponds to the majority point falls to the back of its oplog and gets deleted, this can cause a majority of the secondaries to become too stale to continue replication, and thus require a full resync. Having a majority of a set's nodes being in the process of initial sync would mean that there's no healthy majority to elect a primary, thus the set would then have a prolonged period of no write availability.

      One possible mitigation for this problem is to prevent the primary from deleting ops from its oplog that are ahead or equal to the replication commit point, so that there will always be a common point between the oplogs of the majority of the secondaries and the primary.

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              pavithra.vetriselvan@mongodb.com Pavithra Vetriselvan
              spencer@mongodb.com Spencer Brody (Inactive)
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