[infinispan-issues] [JBoss JIRA] (ISPN-4949) Split brain: data updated in degraded mode

[Radim Vansa (JIRA)]

Radim Vansa created ISPN-4949:
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             Summary: Split brain: data updated in degraded mode
                 Key: ISPN-4949
                 URL: https://issues.jboss.org/browse/ISPN-4949
             Project: Infinispan
          Issue Type: Feature Request
          Components: State Transfer
    Affects Versions: 7.0.0.Final
            Reporter: Radim Vansa
            Priority: Critical


1) cluster A, B, C, D splits into 2 parts:
A, B (coord A) finds this out immediately and enters degraded mode with CH [A, B, C, D]
C, D (coord D) first detects that B is lost, gets view A, C, D and starts rebalance with CH [A, C, D]. Segment X is primary owned by C (it had backup on B but this got lost)
2) D detects that A was lost as well, therefore enters degraded mode with CH [A, C, D]
3) C inserts entry into X: all owners (only C) is present, therefore the modification is allowed
4) cluster is merged and coordinator finds out that the oldest stable topology has CH [A, B, C, D] - logs 'No active or unavailable partitions, so all the partitions must be in degraded mode' (yes, all partitions are in degraded mode, but write has happened in the meantime)
5) The old CH is broadcast in newest topology, no rebalance happens
6) Inconsistency: read in X may miss the update





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