[infinispan-issues] [JBoss JIRA] (ISPN-5720) putForExternalRead may not acquire lock in invalidation mode

[Radim Vansa (JIRA)]

Radim Vansa created ISPN-5720:
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             Summary: putForExternalRead may not acquire lock in invalidation mode
                 Key: ISPN-5720
                 URL: https://issues.jboss.org/browse/ISPN-5720
             Project: Infinispan
          Issue Type: Bug
          Components: Core
    Affects Versions: 8.0.0.Final
            Reporter: Radim Vansa


Usual PutKeyValueCommands go to primary owner to acquire the lock, and then they can safely modify the entry on backup owners.
In invalidation mode, the puts are not distributed (there's no xDistributionInterceptor) and InvalidationInterceptor has special switch for PFER that lets it through. That way, when the PFER is executed on non-primary node, it gets executed without lock being held, potentially overwriting another operation.

The same issue is with all write commands that get invoked with LOCAL_MODE flag. Fixing this is troublesome, since we don't want to lock keys on backup owners too (that would not cause deadlock if done *after* acquiring lock on primary, but it would incur performance hit). However, for PFER specifically we could use putIfAbsent operation on datacontainer during entry commit (this was [~dan.berindei]'s idea).

This could be even generalized to do a compute() check on the container, verifying equality of stored vs. wrapped value, but I am not sure about the consequences.



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