[GitHub] [ozone] ChenSammi edited a comment on pull request #2538: HDDS-5619. Ozone data corruption issue on follower node.

[GitBox <gi...@apache.org>]

ChenSammi edited a comment on pull request #2538:
URL: https://github.com/apache/ozone/pull/2538#issuecomment-903594803


   > 
   > 
   > The issue eventually turned out to be race among write chunk/readChunk threads all using the same file channel. With concurrent writers and readers on the same file, the behaviour seems unpredictable and leads to block file sparseness on disk.
   
   @bshashikant ,  for ContainerStateMachine#read function，I'm not clear about one thing，when  stateMachineDataCache.get(entry.getIndex()) return null， why we cannot think that the data is already written to the disk. 
   
   Thanks @ChenSammi . Usually, the entry will be in stateMachine cahe till the write chunk is applied which means, if a redaStateMachine comes in between till write chunk is not finished, it should be in the cache. But the cache has the entry added only for the leader. Now assume a case like this: 3 servers s1, s2 and s3.  S1 being leader, s2 is fast follower and s3 being the slow follower. S1 sends entry 1 - 100 to S2 and S3 and then S1 dies, S2 has received all the log entries, (yet to complete the write to disk part ) being a follower doesn't update the data cache. Now S2 will be sending append Entries to S3,. S3 might ask for entries from s2 for which the write to disk is not completed neither these entries are in cache, as this node was follower when it received those entries. 


-- 
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.

To unsubscribe, e-mail: issues-unsubscribe@ozone.apache.org

For queries about this service, please contact Infrastructure at:
users@infra.apache.org



---------------------------------------------------------------------
To unsubscribe, e-mail: issues-unsubscribe@ozone.apache.org
For additional commands, e-mail: issues-help@ozone.apache.org