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https://issues.apache.org/jira/browse/ZOOKEEPER-1427?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13404488#comment-13404488
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Rakesh R commented on ZOOKEEPER-1427:
-------------------------------------
Its great. Thanks Todd, Pat
I also come across with the same situation and currentEpoch is coming as empty.
{noformat}
2012-06-28 14:23:13,307 [myid:2] - ERROR [main:QuorumPeer@453] - Unable to load
database on disk
java.io.IOException: Found null in ../dataDir/version-2/currentEpoch
at
org.apache.zookeeper.server.quorum.QuorumPeer.readLongFromFile(QuorumPeer.java:1080)
{noformat}
After analysing found the reason for empty file is due to 'no disk space'.
The patch is really good and proven logic from hdfs. But I'm having one small
clarification. Is there any case in zookeeper to look at the '.tmp' file while
reading back?
Say, (Current/accepted)epoch is 3 and the new epoch 4 has updated into '.tmp'
file. Unfortunately after updating the '.tmp' file, zk got killed. During next
startup whether zk server needs to look at the '.tmp' file as it is having the
highest number than the actual epoch?
-Rakesh
> Writing to local files is done non-atomically
> ---------------------------------------------
>
> Key: ZOOKEEPER-1427
> URL: https://issues.apache.org/jira/browse/ZOOKEEPER-1427
> Project: ZooKeeper
> Issue Type: Bug
> Components: server
> Affects Versions: 3.4.3
> Reporter: Todd Lipcon
> Assignee: Patrick Hunt
> Priority: Critical
> Fix For: 3.4.4, 3.5.0
>
> Attachments: ZOOKEEPER-1427.patch, ZOOKEEPER-1427.patch,
> ZOOKEEPER-1427_br34.patch, ZOOKEEPER-1427_br34.patch
>
>
> Currently, the writeLongToFile() function opens the file for truncate, writes
> the new data, syncs, and then closes. If the process crashes after opening
> the file but before writing the new data, the file may be left empty, causing
> ZK to "forget" an earlier promise. Instead, it should use RandomAccessFile to
> avoid truncating.
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