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https://issues.apache.org/jira/browse/ZOOKEEPER-1465?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13285336#comment-13285336
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Thawan Kooburat commented on ZOOKEEPER-1465:
--------------------------------------------
Even if there are committed proposal but learner is already in-sync, we still
have bug due to this line
// skip the proposals the peer already has
if (propose.packet.getZxid() <= peerLastZxid) {
prevProposalZxid = propose.packet.getZxid();
continue;
}
If this is the last proposal, it will exit the loop and never setup the DIFF
packet. So it will send out the entire snapshot.
This patch seems to work in this case as well.
> 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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