1) DN1->DN2->DN3 are in pipeline.
2) Client killed abruptly
3) one DN has restarted , say DN3
4) In DN3 info.wasRecoveredOnStartup() will be true
5) NN recovery triggered, DN3 skipped from recovery due to above check.
6) Now DN1, DN2 has blocks with generataion stamp 2 and DN3 has older generation stamp say 1 and also DN3 still has this block entry in ongoingCreates
7) as part of recovery file has closed and got only two live replicas ( from DN1 and DN2)
8) So, NN issued the command for replication. Now DN3 also has the replica with newer generation stamp.
9) Now DN3 contains 2 replicas on disk. and one entry in ongoing creates with referring to blocksBeingWritten directory.
When we call append/ leaseRecovery, it may again skip this node for that recovery as blockId entry still presents in ongoingCreates with startup recovery true.
It may keep continue this dance for evry recovery.
And this stale replica will not be cleaned untill we restart the cluster. Actual replica will be trasferred to this node only through replication process.
Also unnecessarily that replicated blocks will get invalidated after next recoveries....