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https://issues.apache.org/jira/browse/KUDU-3098?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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YifanZhang updated KUDU-3098:
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Summary: leadership change during tablet_copy process may lead to an
isolate replica (was: leader change during 'add_peer' process for a tablet may
lead to an isolate replica)
> leadership change during tablet_copy process may lead to an isolate replica
> ---------------------------------------------------------------------------
>
> Key: KUDU-3098
> URL: https://issues.apache.org/jira/browse/KUDU-3098
> Project: Kudu
> Issue Type: Bug
> Components: consensus, master
> Affects Versions: 1.10.1
> Reporter: YifanZhang
> Priority: Major
>
> 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
> {code:java}
> // 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.
> {code}
> Maybe we shouldn't use opid_index to determine if replicas are in the process
> of copying.
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