patrick white created HDFS-6203:
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Summary: check other namenode's state before HAadmin
transitionToActive
Key: HDFS-6203
URL: https://issues.apache.org/jira/browse/HDFS-6203
Project: Hadoop HDFS
Issue Type: Improvement
Components: ha
Affects Versions: 2.3.0
Reporter: patrick white
Current behavior is that the HAadmin -transitionToActive command will complete
the transition to Active even if the other namenode is already in Active state.
This is not an allowed condition and should be handled by fencing, however
setting both namenode's active can happen accidentally with relative ease,
especially in a production environment when performing manual maintenance
operations.
If this situation does occur it is very serious and will likely cause data
loss, or best case, require a difficult recovery to avoid data loss.
This is requesting an enhancement to haadmin's -transitionToActive command, to
have HAadmin check the Active state of the other namenode before completing the
transition. If the other namenode is Active, then fail the request due to other
nn already-active.
Not sure if there is a scenario where both namenode's being Active is valid or
desired, but to maintain functional compatibility a 'force' parameter could be
added to override this check and allow previous behavior.
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