July 2008 - jboss-dev-forums - Jboss List Archives

[Design of Clustering on JBoss (Clusters/JBoss)] - Re: JBAS-5647 HAPartition Sync Call with RspFilter

by galder.zamarreno＠jboss.com

"bstansberry(a)jboss.com" wrote : Yeah, it's kind of hacky, probably a bad idea. Don't do it if the overhead of translating from Address to ClusterNode in the adapter class is small. The overhead looks small, primarily involving some string manipulation. I see that DNS lookups are now avoided thanks to http://jira.jboss.com/jira/browse/JBAS-3794. Clever. I'll make sure I make a note in the code of this potential optimisation in case we wanna implement it at a later stage. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4163681#4163681 Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&p=4163681

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[Design of JBossCache] - Re: Custom data versions

by jason.greene＠jboss.com

Hmm, the addition 2.5 would trigger a deadlock i think. Since both servers will try to aquire a lock on the same fqn. Although the end result would be correct. Implementing the deadlock detection alg would speed up failure as well. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4163679#4163679 Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&p=4163679

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[Design of JBossCache] - Re: Custom data versions

by bstansberry＠jboss.com

Before I get thinking too hard about where the isolated tx gets committed and what transaction is in effect in step 3.... an implementation problem is the code in step 2.5 that "knows it needs to go to the db" is in the core hibernate module, not the JBC integration layer. So some sort of addition would need to be made to the general 2nd level cache API (and implemented by all impls) to support the step 2.5 call. I'll let Steve comment on how he sees that. That said, I understand where you're coming from on wanting to find a way to get rid of this. Will think about it. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4163677#4163677 Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&p=4163677

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[Design of JBossCache] - Re: Custom data versions

by manik.surtani＠jboss.com

Now with MVCC I really don't have a need for data versions internally - the only reason I still use DataVersions is to support custom data versions from Hibernate. I was thinking, maybe there is a way we can achieve the same consistency without the use of data versions? Consider: 1. Server 1 wants to write V2 2. Server 2 wants to read, checks the cache, nothing there, and then decides to go to the DB 3. Server 2 reads V1 from DB 4. Server 1 writes V2 in DB 5. Server 1 puts V2 in cache, invalidates remote caches 6. Server 2 puts V1 in cache, invalidates remote caches And this is the problem, right? What if an additional step is introduced: 2.5. Server 2 knows it needs to go to the DB so it starts an isolated tx, does another cache.get() with a forceWriteLock option. So now Server1's invalidate message will wait until server2 has read v1 and put it in the cache, then the invalidate message will remove it which is correct. Since MVCC allows for non-blocking reads, Server2 will have to check the state of the cache again after acquiring the WL though to see if it still needs to go to the DB incase another reader had read from the DB and updated the cache. (Reminiscent of DCL, thankfully the same ills don't apply here). What do you guys think? View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4163671#4163671 Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&p=4163671

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[Design of JBossCache] - Re: Custom data versions

by bstansberry＠jboss.com

BTW, in the Hibernate integration, the "custom" data version for the structural nodes is one that never returns a version conflict; i.e. the structural nodes hold no data and changing the child map is not treated as a meaningful change, so there can be no meaningful version conflict. This seems like a pretty general use case, so I opened a JIRA to provide such a DataVersion impl in JBC itself: http://jira.jboss.com/jira/browse/JBCACHE-1389 View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4163668#4163668 Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&p=4163668

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[Design of JBossCache] - Re: Custom data versions

by steve.ebersole＠jboss.com

For what it is worth, my initial thought was the interface as well... View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4163665#4163665 Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&p=4163665

17 years, 9 months

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[Design of JBossCache] - Re: Custom data versions

by bstansberry＠jboss.com

That sounds fine to me. In the Hibernate integration most (I think all) calls involve a long tree of structural nodes with a single "data" node at the bottom. Two different custom data versions, one for structural, one for the "data" node. It should be simple for me to implement an optimized Map for that use case; i.e. this approach shouldn't cost much and will eliminate a lot of hassles. Do you want a Map, or perhaps an interface: | public interface DataVersionProvider { | | DataVersion getDataVersion(Fqn fqn); | | } | | If that's the only call JBC is going to make, it would be much simpler to write an optimized version of that vs. Map, where to be correct I'd have to implement a bunch of operations that I don't think would be invoked. | | We could provide a simple helper impl that takes a Map in the constructor and delegates to Map.get(Fqn). View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4163664#4163664 Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&p=4163664

17 years, 9 months

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[Design of JBossCache] - Re: Custom data versions

by manik.surtani＠jboss.com

Just to make things clearer, tombstones are maintained after an invalidation so as long as the *actual* versions are used (v1 and v2 in the example above, which would be custom DataVersion impls from the db) then we are ok. The problem arises where we use DefaultDataVersions which are simple incremented numbers in each JVM. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4163659#4163659 Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&p=4163659

17 years, 9 months

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[Design of JBossCache] - Re: Custom data versions

by manik.surtani＠jboss.com

BTW, the reason why custom data versions are important in Hibernate's use case is detailed below. * Node in DB has v1 * Server1 writes v2 to the cache and the db. * This results in an invalidation message clearing the state of the node in neighbouring Servers. * Server2 does a read from the db before Thread1 completes. Gets v1. * Server2 attempts to put v1 in the cache, but there is a race condition and this happens after Server1's invalidation message comes in. * Server2's put succeeds and Server1's state is invalidated. Caches now have v1 while the db has v2!! View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4163658#4163658 Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&p=4163658

17 years, 9 months

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[Design of JBoss jBPM] - Re: doModelUpdate, doModelRemove in ControllerDomAdapter

by spidek

I didn't asked my question in previous post, and can't edit it, so : Is it possible to add the code above to jbpm ? Or maybe there is better way to do what I need (without patching jbpm) ? Is doModelRemove method in ControllerDomAdapter empty for purpose ? View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4163643#4163643 Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&p=4163643

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jboss-dev-forums July 2008