[infinispan-issues] [JBoss JIRA] (ISPN-11256) Context entries should always be MvccEntries

[Dan Berindei (Jira)]

Dan Berindei created ISPN-11256:
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             Summary: Context entries should always be MvccEntries
                 Key: ISPN-11256
                 URL: https://issues.redhat.com/browse/ISPN-11256
             Project: Infinispan
          Issue Type: Enhancement
          Components: Core
    Affects Versions: 10.1.1.Final
            Reporter: Dan Berindei
             Fix For: 11.0.0.Final


We optimize reads by storing {{InternalCacheEntry}} instances directly in the {{InvocationContext}}, instead of creating a {{ReadCommittedEntry}} or a {{RepeatableReadEntry}}.

This helps {{READ_COMMITTED}} behave like users expect it to, at least in local mode with OBJECT storage: since the context has a reference to the entry in the data container, the transaction sees external updates automatically. I also see this as a negative, though, becase it's practically impossible to extend it to work with distributed caches or with off-heap storage.

The downside is that reading from the entry in the context is racy, so we need {{synchronized}} blocks everywhere, and me may even be missing {{synchronized}} in some places.

It also means that things like {{ReadCommittedEntry.isLoaded()}} don't if the command that triggered the load from the store was a read, because there is no {{ReadCommittedEntry}}.

I suggest always wrapping the entry in a {{MvccEntry}}, and making {{READ_COMMITTED}} caches re-fetch the entry on every read to see external updates (maybe guarded by a flag/configuration attribute). {{SingleKeyNonTxInvocationContext}} may avoid the extra allocation by implementing {{MvccEntry}} itself.



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