Chen Liang created HDFS-14806:
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Summary: Bootstrap standby may fail if used in-progress tailing
Key: HDFS-14806
URL: https://issues.apache.org/jira/browse/HDFS-14806
Project: Hadoop HDFS
Issue Type: Bug
Components: namenode
Affects Versions: 3.3.0
Reporter: Chen Liang
Assignee: Chen Liang
One issue we went across was that if in-progress tailing is enabled, bootstrap
standby could fail.
When in-progress tailing is enabled, Bootstrap uses the RPC mechanism to get
edits. There is a config {{dfs.ha.tail-edits.qjm.rpc.max-txns}} that sets an
upper bound on how many txnid can be included in one RPC call. The default is
5000. Meaning bootstraping NN (say NN1) can only pull at most 5000 edits from
JN. However, as part of bootstrap, NN1 queries another NN (say NN2) for NN2's
current transactionID, NN2 may return a state that is > 5000 txnid from NN1's
current image. But NN1 can only see 5000 more txnid from JNs. At this point NN1
goes panic, because txnid retuned by JNs is behind NN2's returned state,
bootstrap then fail.
Increasing the value of {{dfs.ha.tail-edits.qjm.rpc.max-txns}} to some super
large value allowed bootstrap to continue. But this is hardly the ideal
solution.
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