[infinispan-dev] Question about replication with 5.2.0.CR1

[Randall Hauch]

I'm trying to debug some problems that ModeShape is having in clustered situations when using 5.2.0.CR1. I don't have a standalone test case, but hopefully I can explain what I'm doing.

I'm working with a replicated cache and two processes. The cache configuration (see attached) uses a cache store (with fetchPersistentState=true) and eviction (though the value of 'maxEntries' is high enough that neither process hits it). 

The first process starts up fine and both ModeShape and Infinispan work fine. After some period of time (~20 seconds), I start up the second process. It joins the cluster, and receives the initial state transfer from the first process. I can see from the logs that an entry with a particular key has been transferred and is complete. The second process (as part of the ModeShape initialization code) attempts to look up the entry with this particular key, but it doesn't find it. At this point, ModeShape starts mis-behaving because this particular entry is critical in knowing if ModeShape needs to initialize the repository content (by creating several hundred entries). Upon finding no such node, it attempts to recreate it and a hundred other entries. Some succeed, but others fail because existing entries are found when they weren't expected to be found. I've replicated this problem on two different machines with different operating systems.

We're using explicit locks for writes, and we're using a cache with SKIP_REMOTE_LOOKUP and DELTA_WRITE flags when writing, but no particular flags when reading. (See below for why we're using these flags.)

My understanding is that, once the initial state transfer completes, the second process' cache store should contain all of the transferred entries, and any attempt to look up an entry by key will obviously check local memory and, if not found, will consult the cache store.

I've attached the log file for this second process. Here are some of the key points in the file:

1) Starting with line 39, the log shows that the cache is started, joins the existing cluster, and waits for the initial state transfer. This is follows by lots of lines showing the details of the state transfer.

2) On line 159, one of the state transfer DEBUG lines shows a PutKeyValueCommand with the entry of interest, with key "cb80206317f1e7jcr:system" and who's value looks as expected:

OOB-1,Machine1-27258 2013-01-11 11:31:26,819 TRACE statetransfer.StateTransferInterceptor - handleTopologyAffectedCommand for command PutKeyValueCommand{key=cb80206317f1e7jcr:system, value=SchematicEntryLiteral{ "metadata" : { "id" : "cb80206317f1e7jcr:system" , "contentType" : "application/json" } , "content" : { "key" : "cb80206317f1e7jcr:system" , "parent" : [ "cb80206317f1e7/" , "cb80206cd556c0/" ] , "properties" : { "http://www.jcp.org/jcr/1.0" : { "primaryType" : { "$name" : "mode:system" } } } , "children" : [ { "key" : "cb80206317f1e7jcr:nodeTypes" , "name" : "jcr:nodeTypes" } , { "key" : "cb80206317f1e7jcr:versionStorage" , "name" : "jcr:versionStorage" } , { "key" : "cb80206317f1e7mode:namespaces" , "name" : "mode:namespaces" } , { "key" : "cb80206317f1e7mode:locks" , "name" : "mode:locks" } , { "key" : "cb80206317f1e7mode:synchronizedInitialization" , "name" : "mode:repository" } ] , "childrenInfo" : { "count" : 5 } } }, flags=[CACHE_MODE_LOCAL, SKIP_REMOTE_LOOKUP, PUT_FOR_STATE_TRANSFER, SKIP_SHARED_CACHE_STORE, SKIP_OWNERSHIP_CHECK, IGNORE_RETURN_VALUES, SKIP_XSITE_BACKUP], putIfAbsent=false, lifespanMillis=-1, maxIdleTimeMillis=-1, successful=true}

3) On line 673, the log shows that state transfer was completed.

4) On line 700, ModeShape calls "cache.get(…)" with the "cb80206317f1e7/" key, and this entry is successfully found:

com.pb.spring.Main.main() 2013-01-11 11:31:27,667 TRACE statetransfer.StateTransferInterceptor - handleTopologyAffectedCommand for command GetKeyValueCommand {key=cb80206317f1e7/, flags=null}

5) On line 704, ModeShape calls "cache.get(…)" with the "cb80206317f1e7jcr:system" key, but this entry is not found:

com.pb.spring.Main.main() 2013-01-11 11:31:27,687 TRACE statetransfer.StateTransferInterceptor - handleTopologyAffectedCommand for command GetKeyValueCommand {key=cb80206317f1e7jcr:system, flags=null}

I don't understand why this happens. I understand why the cache doesn't find it in memory, but why doesn't it consult the cache store? Am I missing a specific flag?

Here's a bit of background. Our SchematicEntryLiteral values are DeltaAware, and we've patterned the code after AtomicHashMap to get the MVCC-style behavior, but our SchematicEntryLiteral values contain JSON-like documents. All of our code can be seen at [1]. Notice our SchematicEntryProxy, and the two Delta implementations. We're using explicit locks for writes, and we're using a cache with SKIP_REMOTE_LOOKUP and DELTA_WRITE flags when writing, but no particular flags when reading.

BTW, ModeShape creates two cache containers. One of them (created from the "spectrum-workspace-cache.xml" configuration file) is used only for local in-memory caches that use eviction and no persistence; this cache is not really of concern.

Thanks in advance!

Randall Hauch

[1] https://github.com/rhauch/modeshape/tree/1e0db548891a8355651654d0880553b2635b358f/modeshape-schematic/src/main/java/org/infinispan/schematic/internal

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