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  1. Kudu
  2. KUDU-3098

leadership change during tablet_copy process may lead to an isolate replica



    • Bug
    • Status: Open
    • Major
    • Resolution: Unresolved
    • 1.10.1
    • None
    • consensus, master
    • None


      Lately we found some tablets in a cluster with a very large "time_since_last_leader_heartbeat" metric, they are LEARNER/NON_VOTER and seems couldn't become VOTER for a long time.

      These replicas created during the rebalance/tablet_copy process. After beginning a new copy session from leader to the new added NON_VOTER peer, leadership changed, old leader aborted uncommited CHANGE_CONFIG_OP operation. Finally the tablet_copy session ended but new leader knew nothing about the new peer. 

      Master didn't delete this new added replica because it has a larger opid_index than the latest reported committed config. See the comments in CatalogManager::ProcessTabletReport

      // 5. Tombstone a replica that is no longer part of the Raft config (and
      // not already tombstoned or deleted outright).
      // If the report includes a committed raft config, we only tombstone if
      // the opid_index is strictly less than the latest reported committed
      // config. This prevents us from spuriously deleting replicas that have
      // just been added to the committed config and are in the process of copying.

      Maybe we shouldn't use opid_index to determine if replicas are in the process of copying.




            Unassigned Unassigned
            zhangyifan27 YifanZhang
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