Status: Patch Available
Affects Version/s: 2.7.0
Fix Version/s: None
Release Note:Allow a configuration to specify the maximum number of recovery attempts for blocks under construction.
I found another(?) instance in which the lease is not recovered. This is reproducible easily on a pseudo-distributed single node cluster
- Before you start it helps if you set. This is not necessary, but simply reduces how long you have to wait
- Client starts to write a file. (could be less than 1 block, but it hflushed so some of the data has landed on the datanodes) (I'm copying the client code I am using. I generate a jar and run it using $ hadoop jar TestHadoop.jar)
- Client crashes. (I simulate this by kill -9 the $(hadoop jar TestHadoop.jar) process after it has printed "Wrote to the bufferedWriter"
- Shoot the datanode. (Since I ran on a pseudo-distributed cluster, there was only 1)
I believe the lease should be recovered and the block should be marked missing. However this is not happening. The lease is never recovered.
The effect of this bug for us was that nodes could not be decommissioned cleanly. Although we knew that the client had crashed, the Namenode never released the leases (even after restarting the Namenode) (even months afterwards). There are actually several other cases too where we don't consider what happens if ALL the datanodes die while the file is being written, but I am going to punt on that for another time.