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  1. controller
  2. CONTROLLER-1880

Include conflicting term informantion in AppendEntriesReply

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    Details

    • Type: Improvement
    • Status: Open
    • Priority: Low
    • Resolution: Unresolved
    • Affects Version/s: None
    • Fix Version/s: None
    • Component/s: clustering
    • Labels:
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      Description

      RAFT section 5.3 states that:

      If desired, the protocol can be optimized to reduce the
      number of rejected AppendEntries RPCs. For example,
      when rejecting an AppendEntries request, the follower
      can include the term of the conflicting entry and the first
      index it stores for that term. With this information, the
      leader can decrement nextIndex to bypass all of the con-
      flicting entries in that term; one AppendEntries RPC will
      be required for each term with conflicting entries, rather
      than one RPC per entry. In practice, we doubt this opti-
      mization is necessary, since failures happen infrequently
      and it is unlikely that there will be many inconsistent en-
      tries.

      We currently do not implement this optimization, but it could be useful. From implementation perspective, rather than expanding AppendEntries directly with this information, we should add a subclass, which is used when the follower determines this additional information is useful for leader to skip some entries.

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            Assignee:
            Unassigned Unassigned
            Reporter:
            rovarga Robert Varga
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              Created:
              Updated: