Michi Mutsuzaki created ZOOKEEPER-1653:
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Summary: zookeeper fails to start because of inconsistent epoch
Key: ZOOKEEPER-1653
URL: https://issues.apache.org/jira/browse/ZOOKEEPER-1653
Project: ZooKeeper
Issue Type: Bug
Components: quorum
Affects Versions: 3.4.5
Reporter: Michi Mutsuzaki
It looks like QuorumPeer.loadDataBase() could fail if the server was restarted
after zk.takeSnapshot() but before finishing self.setCurrentEpoch(newEpoch).
{code:java}
case Leader.NEWLEADER: // it will be NEWLEADER in v1.0
zk.takeSnapshot();
self.setCurrentEpoch(newEpoch); // <<< got restarted here
snapshotTaken = true;
writePacket(new QuorumPacket(Leader.ACK, newLeaderZxid, null, null), true);
break;
{code}
The server fails to start because currentEpoch is still 1 but the last
processed zkid from the snapshot has been updated to 2.
{noformat}
2013-02-20 13:45:02,733 5543 [pool-1-thread-1] ERROR
org.apache.zookeeper.server.quorum.QuorumPeer - Unable to load database on disk
java.io.IOException: The current epoch, 1, is older than the last zxid,
8589934592
at
org.apache.zookeeper.server.quorum.QuorumPeer.loadDataBase(QuorumPeer.java:439)
at
org.apache.zookeeper.server.quorum.QuorumPeer.start(QuorumPeer.java:413)
...
{noformat}
{noformat}
$ find datadir
datadir
datadir/version-2
datadir/version-2/currentEpoch.tmp
datadir/version-2/acceptedEpoch
datadir/version-2/snapshot.0
datadir/version-2/currentEpoch
datadir/version-2/snapshot.200000000
$ cat datadir/version-2/currentEpoch.tmp
2%
$ cat datadir/version-2/acceptedEpoch
2%
$ cat datadir/version-2/currentEpoch
1%
{noformat}
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