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https://issues.apache.org/jira/browse/ZOOKEEPER-1692?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13639744#comment-13639744
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Thawan Kooburat commented on ZOOKEEPER-1692:
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The current implementation that I have is to add a flag which modifies the
behavior of FLE for the observers.
With this flag, the observer will look at the leader votes (in outofelection
set). If there is no conflicting votes from the latest epoch (eg. all of the
votes point to the same leader), the observer will try to connect to that
leader. This mechanism only kicks in when notification time out reach its max
value.
The idea behind this is to rely on FLE during normal operation and remove the
majority voting requirement only when the quorum is down for an extended period.
I haven't look at how this feature may interact with dynamic configuration
though.
> Add support for single member ensemble
> --------------------------------------
>
> Key: ZOOKEEPER-1692
> URL: https://issues.apache.org/jira/browse/ZOOKEEPER-1692
> Project: ZooKeeper
> Issue Type: Improvement
> Components: quorum
> Affects Versions: 3.4.0
> Reporter: Thawan Kooburat
> Assignee: Thawan Kooburat
> Priority: Minor
>
> In the past, we ran into problem where quorum could not be formed multiple
> times. It take a while to investigate the root cause and fix the problem.
> Our current solution is to make it possible to run a quorum with a single
> member in it. Unlike standalone mode, it has to run as LeaderZooKeeper
> server, so that the observers can connect to it.
> This will allow the operator to use this workaround to bring back the
> ensemble quickly while investigating the problem in background.
> The main problem here is to allow the observers to connect with the leader
> when the quorum size is reduced to one. We don't want to update the (static)
> configuration on the observer since it require server restart. We are
> thinking of allowing the observer to connect to any participant which
> declared that it is the leader without running the leader election algorithm
> (because it won't have enough votes).
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