[infinispan-dev] Hashing generating recipient lists with same address

Mon May 10 09:59:28 EDT 2010

From https://jira.jboss.org/jira/browse/ISPN-428

Problem: 
1.A starts, B starts see view {A,B} , DistributionManagerImpl.start not called yet because no distributed cache was started 
2. a dist cache is started on A. A's consistent hash sees nodes {A,B} now (as DistributionManagerImpl.start is called) 
3. a dist cache is started on B. The JoinTask fetches A's DCH list of nodes, i.e. {A,B} 
4. B creates a hash function which contains {A,B} (as fetched from A) and itself: {A,B,B} 
--- aftert this point DCH in B is unreliable, anyway here is how the timeout happens 

5. B.put(k,v). B acquires lock on k, then B's DCH indicates that k should be placed on B (!!!). Tries a remote call on B, but it will timeout as the lock on k is already held by user thread that waits 

In other words, the problem is caused by the fact that the joiner doesn't expect itself to be part of the hash function of the remote cache, but it is. I think that the hash function should check for that, and drop duplicates. 

UT is ConcurrentStartWithReplTest

On 7 May 2010, at 16:16, Galder Zamarreno wrote:

> 
> ----- "Mircea Markus" <mircea.markus at jboss.com> wrote:
> 
>> I've tried the the same operation sequence on the caches but it works
>> without timeout. HR server also defines a cache for it's own purposes,
>> I'll try to include that cache as well in the setup and check again.
> 
> Do you have log for the attempt you did to replicate the issue below with only caches and not HR servers? I'd like to see them to verify it.
> 
> The other cache you mention is a replicated cache, for topology info. I don't think it has any bearings here.
> 
>> 
>> On 7 May 2010, at 14:20, Manik Surtani wrote:
>> 
>>> So TopologyChangeTest is a pretty complex test involving HotRod
>> clients and servers, etc.  Can this be reproduced in a simpler setting
>> - i.e., 2 p2p Infinispan instances, add a third, etc., without any
>> HotRod components?
>>> 
>>> On 6 May 2010, at 17:51, galder at redhat.com wrote:
>>> 
>>>> Hi all,
>>>> 
>>>> As indicated on IRC, running
>> org.infinispan.client.hotrod.TopologyChangeTest.testTwoMembers() fails
>> randomly with replication timeout. It's very easy to replicate. When
>> it fails, this is what happens:
>>>> 
>>>> 1. During rehashing, a new hash is installed:
>>>> 2010-05-06 17:54:11,960 4932  TRACE
>> [org.infinispan.distribution.DistributionManagerImpl]
>> (Rehasher-eq-985:) Installing new consistent hash
>> DefaultConsistentHash{addresses ={109=eq-35426, 10032=eq-985,
>> 10033=eq-985}, hash space =10240}
>>>> 
>>>> 2. Rehash finishes and the previous hash is still installed:
>>>> 2010-05-06 17:54:11,978 4950  INFO 
>> [org.infinispan.distribution.JoinTask] (Rehasher-eq-985:) eq-985
>> completed join in 30 milliseconds!
>>>> 
>>>> 3. A put comes in to eq-985 who decides recipients are [eq-985,
>> eq-985]. Most likely, the hash falled somewhere between 109 and 10032
>> and since owners are 2, it took the next 2:
>>>> 2010-05-06 17:54:12,307 5279  TRACE
>> [org.infinispan.remoting.rpc.RpcManagerImpl] (HotRodServerWorker-2-1:)
>> eq-985 broadcasting call
>> PutKeyValueCommand{key=CacheKey{data=ByteArray{size=9,
>> hashCode=d28dfa, array=[-84, -19, 0, 5, 116, 0, 2, 107, 48, ..]}},
>> value=CacheValue{data=ByteArray{size=9, array=[-84, -19, 0, 5, 116, 0,
>> 2, 118, 48, ..]}, version=281483566645249}, putIfAbsent=false,
>> lifespanMillis=-1000, maxIdleTimeMillis=-1000} to recipient list
>> [eq-985, eq-985]
>>>> 
>>>> Everything afterwards is a mess:
>>>> 
>>>> 4. JGroups removes the local address from the destination. The
>> reason Infinispan does not do it it's because the number of recipients
>> is 2 and the number of members in the cluster 2, so it thinks it's a
>> broadcast:
>>>> 2010-05-06 17:54:12,308 5280  TRACE
>> [org.infinispan.remoting.transport.jgroups.CommandAwareRpcDispatcher]
>> (HotRodServerWorker-2-1:) real_dests=[eq-985]
>>>> 
>>>> 5. JGroups still sends it as a broadcast:
>>>> 2010-05-06 17:54:12,308 5280  TRACE [org.jgroups.protocols.TCP]
>> (HotRodServerWorker-2-1:) sending msg to null, src=eq-985, headers are
>> RequestCorrelator: id=201, type=REQ, id=12, rsp_expected=true, NAKACK:
>> [MSG, seqno=5], TCP: [channel_name=Infinispan-Cluster]
>>>> 
>>>> 6. Another node deals with this and replies:
>>>> 2010-05-06 17:54:12,310 5282  TRACE
>> [org.infinispan.remoting.transport.jgroups.CommandAwareRpcDispatcher]
>> (OOB-1,Infinispan-Cluster,eq-35426:) Attempting to execute command:
>> SingleRpcCommand{cacheName='___defaultcache',
>> command=PutKeyValueCommand{key=CacheKey{data=ByteArray{size=9,
>> hashCode=43487e, array=[-84, -19, 0, 5, 116, 0, 2, 107, 48, ..]}},
>> value=CacheValue{data=ByteArray{size=9, array=[-84, -19, 0, 5, 116, 0,
>> 2, 118, 48, ..]}, version=281483566645249}, putIfAbsent=false,
>> lifespanMillis=-1000, maxIdleTimeMillis=-1000}} [sender=eq-985]
>>>> ...
>>>> 
>>>> 7. However, no replies yet from eq-985, so u get:
>>>> 2010-05-06 17:54:27,310 20282 TRACE
>> [org.infinispan.remoting.transport.jgroups.CommandAwareRpcDispatcher]
>> (HotRodServerWorker-2-1:) responses: [sender=eq-985, retval=null,
>> received=false, suspected=false]
>>>> 
>>>> 2010-05-06 17:54:27,313 20285 TRACE
>> [org.infinispan.remoting.rpc.RpcManagerImpl] (HotRodServerWorker-2-1:)
>> replication exception: 
>>>> org.infinispan.util.concurrent.TimeoutException: Replication
>> timeout for eq-985
>>>> 
>>>> Now, I don't understand the reason for creating a hash
>> 10032=eq-985, 10033=eq-985. Shouldn't keeping 10032=eq-985 be enough?
>> Why add 10033=eq-985?
>>>> 
>>>> Assuming there was a valid case for it, a naive approach would be
>> to discard a second node that points to the an address already in the
>> recipient list. So, 10032=eq-985 would be accepted for the list but
>> when encountering 10033=eq-985, this would be skipped.
>>>> 
>>>> Finally, I thought waiting for rehashing to finish would solve the
>> issue but as u can see in 2., rehashing finished and the hash is still
>> in the same shape. Also, I've attached a log file.
>>>> 
>>>> Cheers,
>>>> --
>>>> Galder Zamarreño
>>>> Sr. Software Engineer
>>>> Infinispan, JBoss Cache
>>>> 
>> <bad2_jgroups-infinispan.log.zip>_______________________________________________
>>>> infinispan-dev mailing list
>>>> infinispan-dev at lists.jboss.org
>>>> https://lists.jboss.org/mailman/listinfo/infinispan-dev
>>> 
>>> --
>>> Manik Surtani
>>> manik at jboss.org
>>> Lead, Infinispan
>>> Lead, JBoss Cache
>>> http://www.infinispan.org
>>> http://www.jbosscache.org
>>> 
>>> 
>>> 
>>> 
>>> 
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>> 
>> 
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