[infinispan-issues] [JBoss JIRA] Commented: (ISPN-428) Hashing generating recipient lists with same address

[Mircea Markus (JIRA)]

    [ https://jira.jboss.org/jira/browse/ISPN-428?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12529907#action_12529907 ] 

Mircea Markus commented on 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.

Test: ReplTopologyChangeTest  in core




> Hashing generating recipient lists with same address
> ----------------------------------------------------
>
>                 Key: ISPN-428
>                 URL: https://jira.jboss.org/jira/browse/ISPN-428
>             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
>
>
> 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

-- 
This message is automatically generated by JIRA.
-
If you think it was sent incorrectly contact one of the administrators: https://jira.jboss.org/jira/secure/Administrators.jspa
-
For more information on JIRA, see: http://www.atlassian.com/software/jira