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https://issues.apache.org/jira/browse/ZOOKEEPER-1149?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Patrick Hunt updated ZOOKEEPER-1149:
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Release Note:
The ZooKeeper server cannot be migrated from version 3.4 to version 3.3 and
then back to version 3.4 without user intervention.
Upgrading from 3.3 to 3.4 is supported as is downgrading from 3.4 to 3.3.
However moving from 3.4 to 3.3 and back to 3.4 will fail. 3.4 is checking the
datadir for "acceptedEpoch" and "currentEpoch" files and comparing these
against the snapshot and log files contained in the same directory. These epoch
files are new in 3.4.
As a result:
1) upgrading from 3.3 to 3.4 is fine - the files don't exist, the server
creates them
2) downgrading from 3.4 to 3.3 - this is also fine as version 3.3 ignores these
files
3) however, 3.4->3.3->3.4 fails because 3.4 will see invalid *Epoch files in
the datadir (as 3.3 would have ignored them, applying changes to snap/log w/o
updating them)
A workaround for this problem is to delete the epoch files if this situation
occurrs - the version 3.4 server will create them similar to case 1) above.
How's this? (see the release notes on this jira).
> users cannot migrate from 3.4->3.3->3.4 server code against a single datadir
> ----------------------------------------------------------------------------
>
> Key: ZOOKEEPER-1149
> URL: https://issues.apache.org/jira/browse/ZOOKEEPER-1149
> Project: ZooKeeper
> Issue Type: Task
> Components: server
> Affects Versions: 3.4.0
> Reporter: Patrick Hunt
> Assignee: Patrick Hunt
> Priority: Blocker
> Fix For: 3.4.0
>
>
> 3.4 is checking acceptedEpoch/currentEpoch files against the snap/log files
> in datadir. These files are new in 3.4. If they don't exist the server will
> create them, however if they do exist the server will validate them.
> As a result if a user
> 1) upgrades from 3.3 to 3.4 this is fine
> 2) downgrades from 3.4 to 3.3 this is also fine (3.3 ignores these files)
> 3) however, 3.4->3.3->3.4 fails because 3.4 will see invalid *Epoch files in
> the datadir (as 3.3 would have ignored them, applying changes to snap/log w/o
> updating them)
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