[infinispan-issues] [JBoss JIRA] (ISPN-4995) ClusteredGet served for non-member of CH

[Dan Berindei (JIRA)]

    [ https://issues.jboss.org/browse/ISPN-4995?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13021273#comment-13021273 ] 

Dan Berindei commented on ISPN-4995:
------------------------------------

It's not really possible to guarantee the proper ordering for get results, even without a merge: http://distributedthoughts.wordpress.com/2013/09/08/eventual-consistency/

To apply their example to our non-transactional cache, let's say we have a cluster with nodes {{ABC}}, and {{owners(k) = AB}}.
A {{put(k, v1)}} operation will update the value on node B when it receives the forwarded {{put(k, v1}} command from A, and on node B when it receives the response from B.
If node C issues two {{get(k)}} operations in sequence, the first might receive a response from B after it sent the {{put}} response to A, and the second might receive a response from A before receiving the {{put}} response from B.

In this particular scenario, we could send an OutdatedTopologyException to block the get operation on perf04 until it receives the merged topology, like you suggested on IRC. But that would mean the get operation becomes blocking, and that's against the spirit of Infinispan as a cache.

Besides, we have another level of indirection: if you consider an external client, when the cluster is split in two partitions {{ABC}} and {{D}} but D doesn't know it yet, it could perfectly well read the old value of K1 from D and then the new value of K2 from A. So I'd rather not try to fix this.

I'm more concerned that perf04 reports that it successfully updated the value of both keys when both owners see a JGroups view in which it is not a member. How are you simulating network partitions? I remember JGroups has to allow unicast messages to non-members, otherwise GMS and MERGE2/3 wouldn't work, but I think we could filter those out - unless it turns out to be too expensive.



> ClusteredGet served for non-member of CH
> ----------------------------------------
>
>                 Key: ISPN-4995
>                 URL: https://issues.jboss.org/browse/ISPN-4995
>             Project: Infinispan
>          Issue Type: Bug
>          Components: Core, State Transfer
>            Reporter: Radim Vansa
>            Priority: Critical
>
> When nodes accept ClusteredGetCommand from node that is not member of CH, it can happen that when one thread does
> {code}
> put(K1, V1);
> put(K2, V2)
> {code}
> and another gets
> {code}
> get(K2) -> V2
> get(K1) -> V0 (some old value)
> {code}
> edg-perf01, 02 and 03 share this view and topology:
> {code}
> 04:40:08,714 TRACE [org.jgroups.protocols.FD_SOCK] (INT-8,edg-perf01-63779) edg-perf01-63779: i-have-sock: edg-perf02-45117 --> 172.18.1.3:37476 (cache is {edg-perf01-63779=172.18.1.1:40099, edg-perf02-45117=172.18.1.3:37476})
> 04:40:08,715 TRACE [org.infinispan.topology.ClusterTopologyManagerImpl] (transport-thread--p2-t6) Received new cluster view: 8, isCoordinator = true, becameCoordinator = false
> 04:40:11,203 DEBUG [org.infinispan.topology.LocalTopologyManagerImpl] (transport-thread--p2-t1) Updating local consistent hash(es) for cache testCache: new topology = CacheTopology{id=16, rebalanceId=4, currentC
> H=DefaultConsistentHash{ns = 512, owners = (3)[edg-perf02-45117: 171+170, edg-perf03-6264: 171+171, edg-perf01-63779: 170+171]}, pendingCH=null, unionCH=null, actualMembers=[edg-perf02-45117, edg-perf03-6264, edg-perf01-63779]}
> {code}
> Later, edg-perf02 and edg-perf03 get new view and install a new topology, where edg-perf01 does not exist:
> {code}
> 04:41:13,681 INFO [org.infinispan.remoting.transport.jgroups.JGroupsTransport] (Incoming-2,edg-perf03-6264) ISPN000093: Received new, MERGED cluster view for channel default: MergeView::[edg-perf02-45117|9] (3) [edg-perf02-45117, edg-perf03-6264, edg-perf04-10989], 1 subgroups: [edg-perf04-10989|7] (1) [edg-perf04-10989]
> 04:41:13,681 TRACE [org.infinispan.topology.ClusterTopologyManagerImpl] (transport-thread--p2-t22) Received new cluster view: 9, isCoordinator = false, becameCoordinator = false
> 04:41:13,760 TRACE [org.infinispan.remoting.transport.jgroups.CommandAwareRpcDispatcher] (remote-thread--p3-t32) Attempting to execute non-CacheRpcCommand command: CacheTopologyControlCommand{cache=testCache, type=CH_UPDATE, sender=edg-perf02-45117, joinInfo=null, topologyId=18, rebalanceId=4, currentCH=DefaultConsistentHash{ns = 512, owners = (2)[edg-perf02-45117: 256+85, edg-perf03-6264: 256+86]}, pendingCH=null, availabilityMode=AVAILABLE, actualMembers=[edg-perf02-45117, edg-perf03-6264], throwable=null, viewId=9}[sender=edg-perf02-45117]
> {code}
> After that, edg-perf04 writes to {{key_00000000000020DB}} which is currently owned only by edg-perf03 - this key servers as K1 in example above. It is not backed up to edg-perf01, but edg-perf01 still thinks it's an owner of this key as it did not get any new view (this is a log from edg-perf03) :
> {code}
> 04:41:30,884 TRACE [org.infinispan.remoting.rpc.RpcManagerImpl] (remote-thread--p3-t45) edg-perf03-6264 invoking PutKeyValueCommand{key=key_00000000000020DB, value=[33 #4: 0, 169, 284, 634, ], flags=[SKIP_CACHE_LOAD, SKIP_REMOTE_LOOKUP], putIfAbsent=false, valueMatcher=MATCH_ALWAYS,  metadata=EmbeddedMetadata{version=null}, successful=true} to recipient list [edg-perf03-6264] with options RpcOptions{timeout=60000, unit=MILLISECONDS, fifoOrder=true, totalOrder=false, responseFilter=null, responseMode=SYNCHRONOUS, skipReplicationQueue=false}
> {code}
> Later, edg-perf04 writes to another key {{stressor_33}} (K2 in the example) value with operationId=650 (previous value is 600) which is replicated to edg-perf02 and edg-perf03.
> Now a merge view with all 4 nodes is installed:
> {code}
> 04:41:31,258 INFO  [org.infinispan.remoting.transport.jgroups.JGroupsTransport] (Incoming-2,edg-perf01-63779) ISPN000093: Received new, MERGED cluster view for channel default: MergeView::[edg-perf01-63779|10] (4) [edg-perf01-63779, edg-perf03-6264, edg-perf02-45117, edg-perf04-10989], 6 subgroups: [edg-perf02-45117|7] (2) [edg-perf02-45117, edg-perf03-6264], [edg-perf01-63779|4] (2) [edg-perf01-63779, edg-perf02-45117], [edg-perf02-45117|9] (3) [edg-perf02-45117, edg-perf03-6264, edg-perf04-10989], [edg-perf03-6264|4] (2) [edg-perf03-6264, edg-perf04-10989], [edg-perf01-63779|8] (3) [edg-perf01-63779, edg-perf02-45117, edg-perf03-6264], [edg-perf01-63779|6] (1) [edg-perf01-63779]
> 04:41:31,258 TRACE [org.infinispan.topology.ClusterTopologyManagerImpl] (transport-thread--p2-t2) Received new cluster view: 10, isCoordinator = true, becameCoordinator = false
> {code}
> edg-perf01 now issues a remote get to edg-perf02 for key stressor_33 and receives the correct answer (operationId=650):
> {code}
> 04:41:32,494 TRACE [org.infinispan.remoting.rpc.RpcManagerImpl] (BackgroundOps-Checker-1) Response(s) to ClusteredGetCommand{key=stressor_33, flags=null} is {edg-perf02-45117=SuccessfulResponse{responseValue=ImmortalCacheValue {value=LastOperation{operationId=650, seed=0000A15A4C2DD25A}}} }
> {code}
> However, when edg-perf01 reads {{key_00000000000020DB}}, it loads the old value from local data container as no CH update/rebalance happened so far:
> {code}
> 04:41:32,496 TRACE [org.infinispan.partitionhandling.impl.PartitionHandlingManagerImpl] (BackgroundOps-Checker-1) Checking availability for key=key_00000000000020DB, status=AVAILABLE
> 04:41:32,497 ERROR [org.radargun.stages.cache.background.LogChecker] (BackgroundOps-Checker-1) Missing operation 634 for thread 33 on key 8411 (key_00000000000020DB) 
> 04:41:32,499 DEBUG [org.radargun.service.InfinispanDebugable] (BackgroundOps-Checker-1) Debug info for key testCache key_00000000000020DB: owners=edg-perf01-63779, edg-perf03-6264, local=true, uncertain=false, container.key_00000000000020DB=ImmortalCacheEntry[key=key_00000000000020DB, value=[33 #3: 0, 169, 284, ], created=-1, isCreated=false, lastUsed=-1, isChanged=false, expires=-1, isExpired=false, canExpire=false, isEvicted=true, isRemoved=false, isValid=false, lifespan=-1, maxIdle=-1], segmentId=173
> {code}
> Note that this was found on branch https://github.com/infinispan/infinispan/pull/3062/files trying to fix ISPN-4949.



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