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https://issues.apache.org/jira/browse/IGNITE-17738?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Maxim Muzafarov updated IGNITE-17738:
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Fix Version/s: 2.15
> Cluster must be able to fix the inconsistency on restart/node_join by itself
> ----------------------------------------------------------------------------
>
> Key: IGNITE-17738
> URL: https://issues.apache.org/jira/browse/IGNITE-17738
> Project: Ignite
> Issue Type: Sub-task
> Reporter: Anton Vinogradov
> Assignee: Maxim Muzafarov
> Priority: Major
> Labels: iep-31, ise
> Fix For: 2.15
>
> Attachments: PartialHistoricalRebalanceTest.java,
> SkippedRebalanceBecauseOfTheSameLwmTest.java
>
>
> On cluster restart (because of power-off, OOM or some other problem) it's
> possible to have PDS inconsistent (primary partitions may contain operations
> missed on backups as well as counters may contain gaps even on primary).
> 1) Currently, "historical rebalance" is able to sync the data to the highest
> LWM for every partition.
> Most likely, a primary will be chosen as a rebalance source, but the data
> after the LWM will not be rebalanced. So, all updates between LWM and HWM
> will not be synchronized.
> See [^PartialHistoricalRebalanceTest.java]
> Such partition may be rebalanced correctly "later" in case of full rebalance
> will be triggered sometime.
> 2) In case LWM is the same on primary and backup, rebalance will be skipped
> for such partition.
> See [^SkippedRebalanceBecauseOfTheSameLwmTest.java]
> Proposals:
> 1) Cheap fix
> A possible solution for the case when the cluster failed and restarted (same
> baseline) is to fix the counters automatically (when cluster composition is
> equal to the baseline specified before the crash).
> Counters should be set as
> - HWM at primary and as LWM at backups for caches with 2+ backups,
> - LWM at primary and as HWM at backups for caches with a single backup.
> 2) Correct fix
> Rebalance must honor whole counter state (LWM, HWM, gaps).
> 2.0) Primary HWM must be set to the highest HWM across the copies to avoid
> reapplying of already applied update counters on backups.
> 2.1) In case when WAL is available all entries between LWM and HWM
> (including) must be rebalanced to other nodes where they are required.
> Even from backups to the primary.
> 2.2) Full rebalance must be restricted when it causes any updates loss.
> For example, it's
> - ok to replace B with A when
> A[lwm=100, gaps=[142], hwm=200] and B[lwm=50, gaps=[76,99,111], hwm=120],
> because A contains whole B.
> - NOT ok to replace B with A when
> A[lwm=100, gaps=[142], hwm=200] and B[lwm=50, gaps=[76,99,111],
> hwm={*}148{*}],
> when update *142* will be lost.
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