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From "Rahul Singhal (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HDFS-6339) DN, SNN & JN can't rollback data
Date Sun, 04 May 2014 16:21:14 GMT
Rahul Singhal created HDFS-6339:

             Summary: DN, SNN & JN can't rollback data
                 Key: HDFS-6339
                 URL: https://issues.apache.org/jira/browse/HDFS-6339
             Project: Hadoop HDFS
          Issue Type: Bug
          Components: journal-node
    Affects Versions: 2.2.0
            Reporter: Rahul Singhal

I tried rollback from 2.4.0 to 2.2.0 and noticed that DN, SNN and JN couldn't perform rollback.

I started with a (NN) HA cluster on 2.2.0 and upgraded it to 2.4.0 with HA enabled. Then attempted
a rollback to 2.2.0. I first configured my cluster to non-HA and started it on 2.2.0. I started
NN & DN with the '-rollback' startup option. (There is no explicit startup option for
SNN & JN like NN & DN). Only NN was able to rollback correctly.

My fixes:
I fixed the DN rollback problem by cherry-picking the fix from HDFS-5526.
I fixed the SNN rollback problem by starting it with '-format' option.

I then proceeded to converting the non-HA cluster to a HA cluster. The first step after configuration
change was to start the JNs. But they also couldn't rollback.

My fix:
I fixed this by deleting the JN data directory. (deleting the 'current' directory and renaming
'previous' to 'current' didn't fix the rollback)

My purpose for filing this bug is to:
1. Ask if these problems are known and intended to be fixed in any future releases. If yes,
which one? DN rollback was fixed in 2.3.0 but what about 2.2.x series? JN rollback seems (not
confirmed) to have been fixed in 2.4.0.
2. Confirm that "my fixes" are correct. If not, please help me with an appropriate fix.

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