[infinispan-issues] [JBoss JIRA] (ISPN-8962) PreferAvailabilityStrategy: Rely less on the stable topology

[William Burns (JIRA)]

     [ https://issues.jboss.org/browse/ISPN-8962?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

William Burns updated ISPN-8962:
--------------------------------
        Status: Resolved  (was: Pull Request Sent)
    Resolution: Done


> PreferAvailabilityStrategy: Rely less on the stable topology
> ------------------------------------------------------------
>
>                 Key: ISPN-8962
>                 URL: https://issues.jboss.org/browse/ISPN-8962
>             Project: Infinispan
>          Issue Type: Bug
>          Components: Core
>    Affects Versions: 9.2.0.Final
>            Reporter: Dan Berindei
>            Assignee: Dan Berindei
>             Fix For: 9.2.2.Final, 9.3.0.Final
>
>
> {{PreferAvailabilityStrategy}} checks the size of the stable topology, and only considers cache topologies that are derived from the biggest topology (in size) when picking a post-merge topology.
> Unfortunately, in some situations this algorithm fails pretty badly. If a node has a very long GC pause, when it comes back it will report the old topology *and* the old stable topology. If the rest of the cluster rebalanced, it now has both a smaller current topology and a smaller stable topology.
> Furthermore, the stable topology is updated asynchronously, independent from the current topology. So even if there's a split and the minority partition installs a current topology with fewer members, it may take some time for its stable topology to be updated with fewer members. In fact, it appears that when a rebalance is not needed (e.g. because the partition has a single node), the stable topology is never updated!



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