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https://issues.apache.org/jira/browse/RATIS-800?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17150915#comment-17150915
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runzhiwang edited comment on RATIS-800 at 7/3/20, 11:36 AM:
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1. Add (selfPriority, targetPriority) to each group member, the member can
trigger a leader election if selfPriority > targetPriority. For example, when
init group,
we can set the suggested leader with (targetPriority + 100, targetPriority),
and the two follower with (targetPriority - 100, targetPriority) and
(targetPriority - 200, targetPriority), so only the suggested leader can
trigger leader election and will be elected as a leader.
2. But if the leader crash, two follower can not trigger leader election
because selfPriority < targetPriority. To address this, if follower can not
trigger leader election, and after a time threshold, there is no leader was
elected, follower will decrease it's targetPriority at a fix rate such as 20%
until selfPriority > targetPriority. After leader was elected, all followers
set targetPriority = selfPriority + randomValue in a range.
3. After cluster run a long time, leader election happen a lot of times, maybe
leader is not balance among datanode, so we need to re-balance leader by force
change leader to some datanode with low load. For example, datanode1 is a
leader of group1 and group2, we can change the leader of group2 from datanode1
to datanode2 by ask datanode2 trigger a election.
[~szetszwo][~ljain][~msingh][~shashikant] Could you help review this proposal ?
Thank you very much.
was (Author: yjxxtd):
1. Add (selfPriority, targetPriority) to each group member, the member can
trigger a leader election if selfPriority > targetPriority. For example, when
init group,
we can set the suggested leader with (targetPriority + 100, targetPriority),
and the two follower with (targetPriority - 100, targetPriority) and
(targetPriority - 200, targetPriority), so only the suggested leader can
trigger leader election and will be elected as a leader.
2. But if the leader crash, two follower can not trigger leader election
because selfPriority < targetPriority. To address this, if follower can not
trigger leader election, and after a time threshold, there is no leader was
elected, follower will decrease it's targetPriority at a fix rate such as 20%
until selfPriority > targetPriority.
3. After cluster run a long time, leader election happen a lot of times, maybe
leader is not balance among datanode, so we need to re-balance leader by force
change leader to some datanode with low load. For example, datanode1 is a
leader of group1 and group2, we can change the leader of group2 from datanode1
to datanode2 by ask datanode2 trigger a election.
[~szetszwo][~ljain][~msingh][~shashikant] Could you help review this proposal ?
Thank you very much.
> Make Ratis consume recommended leader host from the pipeline creator
> --------------------------------------------------------------------
>
> Key: RATIS-800
> URL: https://issues.apache.org/jira/browse/RATIS-800
> Project: Ratis
> Issue Type: Sub-task
> Reporter: Li Cheng
> Assignee: runzhiwang
> Priority: Critical
>
> Start a Jira for suggested leader sematics. It would help Ratis performance
> if it can consume the leader host which its upstream user like Ozone
> recommends. User can choose the leader host based on load balance and rack
> awareness.Â
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