Todd Lipcon created HDFS-3797:
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Summary: QJM: add segment txid as a parameter to journal() RPC
Key: HDFS-3797
URL: https://issues.apache.org/jira/browse/HDFS-3797
Project: Hadoop HDFS
Issue Type: Sub-task
Components: ha
Affects Versions: QuorumJournalManager (HDFS-3077)
Reporter: Todd Lipcon
Assignee: Todd Lipcon
Priority: Minor
During fault testing of QJM, I saw the following issue:
1) NN sends txn 5 to JN
2) NN gets partitioned from JN while JN remains up. The next two RPCs are
missed while the partition has happened:
2a) finalizeSegment(1-5)
2b) startSegment(6)
3) NN sends txn 6 to JN
This caused one of the JNs to end up with a segment 1-10 while the others had
two segments; 1-5 and 6-10. This broke some invariants of the QJM protocol and
prevented the recovery protocol from running properly.
This can be addressed on the client side by HDFS-3726, which would cause the NN
to not send the RPC in #3. But it makes sense to also add an extra safety check
here on the server side: with every journal() call, we can send the segment's
txid. Then if the JN and the client get "out of sync", the JN can reject the
RPCs.
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