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  1. Cassandra
  2. CASSANDRA-14744

TR transient -> full and full -> transient enters pending state reducing availability

    Details

    • Type: Improvement
    • Status: Resolved
    • Priority: Normal
    • Resolution: Not A Problem
    • Fix Version/s: 4.x
    • Component/s: Legacy/Core
    • Labels:
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      Description

      A transient replica transitioning to full and vice versa doesn't cease to be the kind of replica it used to be before. I think this could cause availability issues if a node goes down and it could even cause unavailable with some ring movements with all nodes up. I haven't convinced myself 100% this is true, but I think it should be possible to construct an example.

      We can't read from pending replicas so if a ring movement were to make 2/3 out of a group of 3 pending we would have this problem.

      The key difference here is that the existing replica should be available during this period as the kind of replica it was before. A full replica remains full until nodetool cleanup is run. A transient replica remains transient the entire time.

      Obviously this doesn't hold for transitions to/from not replicated at all.

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              • Assignee:
                Unassigned
                Reporter:
                aweisberg Ariel Weisberg
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