]
Manik Surtani commented on ISPN-425:
------------------------------------
Right, it looks like you have 2 distinct problems here, clouded together by the fact that
you sometimes have L1-on-rehash set to true.
I think the issue with a PUT on a Joiner before rehash completes is a pretty odd bug (how
did you get to do this PUT in the first place - cache.start() shouldn't return until
the join - and rehash - is complete!)
The second issue is with invalidation while an entry is being rehashed/moved. E.g.,
"old" owner C2 should accept an invalidation event and not reject it, claiming
ownership.
Again, if you could separate your test to isolate these two cases that would make things
clearer.
Stale data read when L1 invalidation happens while
UnionConsistentHash is in use
--------------------------------------------------------------------------------
Key: ISPN-425
URL:
https://jira.jboss.org/jira/browse/ISPN-425
Project: Infinispan
Issue Type: Bug
Components: Distributed Cache
Affects Versions: 4.1.0.BETA1
Reporter: Galder Zamarreno
Assignee: Galder Zamarreno
Priority: Blocker
Fix For: 4.1.0.CR1
Attachments: infinispan_isL1OnRehash_false.log,
infinispan_isL1OnRehash_true.log.zip
See below:
----- "Manik Surtani" <manik(a)jboss.org> wrote:
> On 3 May 2010, at 08:51, Galder Zamarreno wrote:
>
> > Resending without log until the message is approved.
> >
> > --
> > Galder ZamarreƱo
> > Sr. Software Engineer
> > Infinispan, JBoss Cache
> >
> > ----- Forwarded Message -----
> > From: galder(a)redhat.com
> > To: "infinispan -Dev List" <infinispan-dev(a)lists.jboss.org>
> > Sent: Friday, April 30, 2010 6:30:05 PM GMT +01:00 Amsterdam /
> Berlin / Bern / Rome / Stockholm / Vienna
> > Subject: Stale data read when L1 invalidation happens while
> UnionConsistentHash is in use
> >
> > Hi,
> >
> > I've spent all day chasing down a random Hot Rod testsuite failure
> related to distribution. This is the last hurdle to close
>
https://jira.jboss.org/jira/browse/ISPN-411. In
> HotRodDistributionTest, which is still to be committed, I test adding
> a new node, doing a put on this node, and then doing a get in a
> different node and making sure that I get what was put. The test
> randomly fails saying that the get returns the old value. The failure
> is nothing to do with Hot Rod itself but rather a race condition where
> union consistent hash is used. Let me explain:
> >
> > 1. An earlier operation had set
> "k-testDistributedPutWithTopologyChanges" key to
> "v5-testDistributedPutWithTopologyChanges".
> > 2. Start a new hot rod server in eq-7969.
> > 2. eq-7969 node calls a put on that key with
> "v6-testDistributedPutWithTopologyChanges". Recipients for the put
> are: eq-7969 and eq-61332.
> > 3. eq-7969 sends an invalidate L1 to all, including eq-13415
> > 4. eq-13415 should invalidate
> "k-testDistributedPutWithTopologyChanges" but it doesn't, since it
> considers that "k-testDistributedPutWithTopologyChanges" is local to
> eq-13415:
> >
> > 2010-04-30 18:02:19,907 6046 TRACE
> [org.infinispan.distribution.DefaultConsistentHash]
> (OOB-2,Infinispan-Cluster,eq-13415:) Hash code for key
> CacheKey{data=ByteArray{size=39, hashCode=17b1683, array=[107, 45,
> 116, 101, 115, 116, 68, 105, 115, 116, ..]}} is 344897059
> > 2010-04-30 18:02:19,907 6046 TRACE
> [org.infinispan.distribution.DefaultConsistentHash]
> (OOB-2,Infinispan-Cluster,eq-13415:) Candidates for key
> CacheKey{data=ByteArray{size=39, hashCode=17b1683, array=[107, 45,
> 116, 101, 115, 116, 68, 105, 115, 116, ..]}} are {5458=eq-7969,
> 6831=eq-61332}
> > 2010-04-30 18:02:19,907 6046 TRACE
> [org.infinispan.distribution.DistributionManagerImpl]
> (OOB-2,Infinispan-Cluster,eq-13415:) Is local
> CacheKey{data=ByteArray{size=39, hashCode=17b1683, array=[107, 45,
> 116, 101, 115, 116, 68, 105, 115, 116, ..]}} to eq-13415 query returns
> true and consistentHash is
> org.infinispan.distribution.UnionConsistentHash@10747b4
> >
> > This is a log with log messages that I added to debug it. The key
> factor here is that UnionConsistentHash is in use, probably due to
> rehashing not having fully finished.
> >
> > 5. The end result is that a read of
> "k-testDistributedPutWithTopologyChanges" in eq-13415 returns
> "v5-testDistributedPutWithTopologyChanges".
> >
> > I thought that maybe we could be more conservative here and if
> rehashing is in progress (or UnionConsistentHash is in use) invalidate
> regardless. Assuming that a put always follows an invalidation in
> distribution and not viceversa, that would be fine. The only downside
> is that you'd be invalidating too much but put would replace the data
> in the node where invalidation should not have happened but it did, so
> not a problem.
> >
> > Thoughts? Alternatively, maybe I need to shape my test so that I
> wait for rehashing to finish, but the problem would still be there.
>
> Yes, this seems to be a bug with concurrent rehashing and invalidation
> rather than HotRod.
>
> Could you modify your test to so the following:
>
> 1. start 2 caches C1 and C2.
> 2. put a key K such that K maps on to C1 and C2
> 3. add a new node, C3. K should now map to C1 and C3.
> 4. Modify the value on C1 *before* rehashing completes.
> 5. See if we see the stale value on C2.
>
> To do this you would need a custom object for K that hashes the way
> you would expect (this could be hardcoded) and a value which blocks
> when serializing so we can control how long rehashing takes.
Since logical addresses are used underneath and these change from one run to the other,
I'm not sure how I can generate such key programatically. It's even more
complicated to figure out a key that will later, when C3 starts, map to it. Without having
these addresses locked somehow, or their hash codes, I can't see how this is doable.
IOW, to be able to do this, I need to mock these addresses into giving fixed as hash
codes. I'll dig further into this.
>
> I never promised the test would be simple! :)
>
> Cheers
> Manik
> --
> Manik Surtani
> manik(a)jboss.org
> Lead, Infinispan
> Lead, JBoss Cache
>
http://www.infinispan.org
>
http://www.jbosscache.org
>
>
>
>
>
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>
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