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https://issues.apache.org/jira/browse/ZOOKEEPER-1465?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13287436#comment-13287436
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Camille Fournier commented on ZOOKEEPER-1465:
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Thawan, that's a good idea. It's not a bigger change to change the
packetToSend=DIFF when we enter the if((maxCommittedLog >=peerLastZxid) &&
(minCommittedLog <= peerLastZxid)) instead of putting the hack where I stuck
it. Do you want to modify my patch and see if it still works?
Flavio, I'm not sure how we can have a snapshot to send when we don't have a
committedLog. Can you clarify? Either the requests are committed, or they
should be in the toBeApplied list on the Leader and so the peer will get them
when startForwarding is called with the peer's last zxid.
> Cluster availability following new leader election takes a long time with
> large datasets - is correlated to dataset size
> ------------------------------------------------------------------------------------------------------------------------
>
> Key: ZOOKEEPER-1465
> URL: https://issues.apache.org/jira/browse/ZOOKEEPER-1465
> Project: ZooKeeper
> Issue Type: Bug
> Components: leaderElection
> Affects Versions: 3.4.3
> Reporter: Alex Gvozdenovic
> Assignee: Camille Fournier
> Priority: Critical
> Fix For: 3.4.4
>
> Attachments: ZOOKEEPER-1465.patch
>
>
> When re-electing a new leader of a cluster, it takes a long time for the
> cluster to become available if the dataset is large
> Test Data
> ----------
> 650mb snapshot size
> 20k nodes of varied size
> 3 member cluster
> On 3.4.x branch
> (http://svn.apache.org/repos/asf/zookeeper/branches/branch-3.4?r=1244779)
> ------------------------------------------------------------------------------------------
> Takes 3-4 minutes to bring up a cluster from cold
> Takes 40-50 secs to recover from a leader failure
> Takes 10 secs for a new follower to join the cluster
> Using the 3.3.5 release on the same hardware with the same dataset
> -----------------------------------------------------------------
> Takes 10-20 secs to bring up a cluster from cold
> Takes 10 secs to recover from a leader failure
> Takes 10 secs for a new follower to join the cluster
> I can see from the logs in 3.4.x that once a new leader is elected, it pushes
> a new snapshot to each of the followers who need to save it before they ack
> the leader who can then mark the cluster as available.
> The kit being used is a low spec vm so the times taken are not relevant per
> se - more the fact that a snapshot is always sent even through there is no
> difference between the persisted state on each peer.
> No data is being added to the cluster while the peers are being restarted.
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