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Posted to dev@zookeeper.apache.org by "Jeremy Stribling (Updated) (JIRA)" <ji...@apache.org> on 2011/12/06 04:07:45 UTC
[jira] [Updated] (ZOOKEEPER-1319) Missing data after
restarting+expanding a cluster
[ https://issues.apache.org/jira/browse/ZOOKEEPER-1319?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Jeremy Stribling updated ZOOKEEPER-1319:
----------------------------------------
Attachment: logs.tgz
Contains two logs, one for server 0 and one for server 1. The logs are annotated to describe where the cluster was restarted.
> Missing data after restarting+expanding a cluster
> -------------------------------------------------
>
> Key: ZOOKEEPER-1319
> URL: https://issues.apache.org/jira/browse/ZOOKEEPER-1319
> Project: ZooKeeper
> Issue Type: Bug
> Affects Versions: 3.4.0
> Environment: Linux (Debian Squeeze)
> Reporter: Jeremy Stribling
> Labels: cluster, data
> Attachments: logs.tgz
>
>
> I've been trying to update to ZK 3.4.0 and have had some issues where some data become inaccessible after adding a node to a cluster. My use case is a bit strange (as explained before on this list) in that I try to grow the cluster dynamically by having an external program automatically restart Zookeeper servers in a controlled way whenever the list of participating ZK servers needs to change. This used to work just fine in 3.3.3 (and before), so this represents a regression.
> The scenario I see is this:
> 1) Start up a 1-server ZK cluster (the server has ZK ID 0).
> 2) A client connects to the server, and makes a bunch of znodes, in particular a znode called "/membership".
> 3) Shut down the cluster.
> 4) Bring up a 2-server ZK cluster, including the original server 0 with its existing data, and a new server with ZK ID 1.
> 5) Node 0 has the highest zxid and is elected leader.
> 6) A client connecting to server 1 tries to "get /membership" and gets back a -101 error code (no such znode).
> 7) The same client then tries to "create /membership" and gets back a -110 error code (znode already exists).
> 8) Clients connecting to server 0 can successfully "get /membership".
> I will attach a tarball with debug logs for both servers, annotating where steps #1 and #4 happen. You can see that the election involves a proposal for zxid 110 from server 0, but immediately following the election server 1 has these lines:
> 2011-12-05 17:18:48,308 9299 [QuorumPeer[myid=1]/127.0.0.1:2901] WARN org.apache.zookeeper.server.quorum.Learner - Got zxid 0x100000001 expected 0x1
> 2011-12-05 17:18:48,313 9304 [SyncThread:1] INFO org.apache.zookeeper.server.persistence.FileTxnLog - Creating new log file: log.100000001
> Perhaps that's not relevant, but it struck me as odd. At the end of server 1's log you can see a repeated cycle of getData->create->getData as the client tries to make sense of the inconsistent responses.
> The other piece of information is that if I try to use the on-disk directories for either of the servers to start a new one-node ZK cluster, all the data are accessible.
> I haven't tried writing a program outside of my application to reproduce this, but I can do it very easily with some of my app's tests if anyone needs more information.
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