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https://issues.apache.org/jira/browse/IGNITE-9913?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16871096#comment-16871096
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Amelchev Nikita commented on IGNITE-9913:
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Hi, [~ivan.glukos].
I found two possible blockers to do such lightweight PME without blocking
updates:
1. Finalize partitions counter. It seems that we can't correctly collect gaps
and process them without completing all txs. See the
{{GridDhtPartitionTopologyImpl#finalizeUpdateCounters}} method.
2. Apply update counters. We can't correctly set {{HWM}} counter if primary
left the cluster and sent updates to part of backups. Such updates can be
processed later and break guarantee that {{LWM<=HWM}}.
Could you take a look?
> Prevent data updates blocking in case of backup BLT server node leave
> ---------------------------------------------------------------------
>
> Key: IGNITE-9913
> URL: https://issues.apache.org/jira/browse/IGNITE-9913
> Project: Ignite
> Issue Type: Improvement
> Components: general
> Reporter: Ivan Rakov
> Assignee: Amelchev Nikita
> Priority: Major
> Fix For: 2.8
>
> Attachments: 9913_yardstick.png, master_yardstick.png
>
> Time Spent: 50m
> Remaining Estimate: 0h
>
> Ignite cluster performs distributed partition map exchange when any server
> node leaves or joins the topology.
> Distributed PME blocks all updates and may take a long time. If all
> partitions are assigned according to the baseline topology and server node
> leaves, there's no actual need to perform distributed PME: every cluster node
> is able to recalculate new affinity assigments and partition states locally.
> If we'll implement such lightweight PME and handle mapping and lock requests
> on new topology version correctly, updates won't be stopped (except updates
> of partitions that lost their primary copy).
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