Thanks,
On Mon, Jan 14, 2013 at 6:53 AM, Randall Hauch <rhauch(a)redhat.com> wrote:
We're using MODE-1745 to track this problem (from
ModeShape's
perspective):
https://issues.jboss.org/browse/MODE-1745
Here's an update.
After some more extensive debugging sessions, found the following in the
scenario when the 2nd cluster nodes is started only after the first
clustered node has completed initialization:
• state transfer seems to be sending all the data across to node 2
from node 1 - in total 293 PutKeyValueCommand
• when the systemNode == null check is performed on node 2, the
cache only has 222 entries and there is nothing persisted in the file cache
store
This seems to be a case of nodes being evicted from node 2, without being
persisted on the underlying cache store. Disabling eviction via the
configuration file make this scenario pass. With the latter set to NONE,
all the 293 entries received by node 2 are placed in the data container.
With the eviction set to
<eviction strategy="LIRS" maxEntries="1000"/>
only 222 entries (out of 293 total) are placed in the cache. This
indicates to Horia and I that there's a possible bug
aroundorg.infinispan.container.DefaultDataContainer#put
/org.infinispan.util.concurrent.BoundedConcurrentHashMap (the actual
runtime instance) and eviction.
Running with:
<eviction strategy="LRU" maxEntries="10000"/>
produces the same problem, so ATM we're able to run successfully **ONLY**
with eviction disabled.
Can someone familiar with Infinispan's internals please take a look at
this to see if we're correct?
On Jan 11, 2013, at 12:03 PM, Randall Hauch <rhauch(a)redhat.com> wrote:
> 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/1e0db548891a8355651654d0880553b2...
>
>
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