[jbosscache-dev] Re: Session Clustering for SIP
Brian Stansberry
brian.stansberry at redhat.com
Thu May 22 08:05:30 EDT 2008
Copying to jbosscache-dev list. Jean, since you're doing caching work,
suggest you subscribe to that list if you haven't already.
I think your suggestion is definitely worth considering. If I understand
you correctly, you're basically proposing something like adding a
replication-trigger config to JBC, whereby with
SET_AND_NON_PRIMITIVE_GET, JBC would track the type of any read and if
not primitive, generate a cluster-wide write at transaction commit.
Jean Deruelle wrote:
> Hi Brian,
>
> Thinking a bit more about this.
> You seems to have achieved in http sessions what is not possible to do
> with Jboss cache natively and that is to me a drawback for Jboss Cache
> ease of use.
>
> It is monitor automatically any changes to an object even if its
> bytecode has not been enhanced by JBoss AOP...
> Do you think it would not be better to integrate your code into Jboss
> Cache this could help us to have a cleaner code and benefit others ?
> Maybe with a note saying that it's less performing than if you
> preprocess your classes with Jboss AOP (if my guess that it is less
> performing is right...)
>
> wdyt ?
> Best regards
> Jean
>
> Brian Stansberry wrote:
>> Jean Deruelle wrote:
>>> Brian Stansberry wrote:
>>> <snip/>
>>>>
>>>>>>> As a first version, I intend to try to keep things as simple as
>>>>>>> possible so my plan is "just" to store the complete SipSession
>>>>>>> object I have into the cache and let TreeCacheAop do the job when
>>>>>>> attributes are added/modified/removed to replicate to other node(s).
>>>>>>>
>>>>>>> I was looking at the AttributeBasedClusteredSession
>>>>>>> implementation and one thing I fail to understand is why it is
>>>>>>> using a lot of transient map to handle session attributes (all
>>>>>>> attibutes, only modified, only removed Maps) instead of letting
>>>>>>> the Cache handling that for you ? Even for replication it seems
>>>>>>> to be done by hand through the storeSession method of the
>>>>>>> JbossCacheManager class and the SnapshotManager class ?
>>>>>>>
>>>>>>
>>>>>> This mostly relates to not forcing the user to have to remember to
>>>>>> call setAttribute if they modify an attribute:
>>>>>>
>>>>>> Set set = session.getAttribute("set");
>>>>>> set.add(someObject);
>>>>>> // oops, forgot to call setAttribute, updated set doesn't replicate!
>>>>>>
>>>>> I thought and still think this is not needed with TreeCacheAop in
>>>>> doing putObject instead of put (see
>>>>> http://www.jboss.org/file-access/default/members/jbosscache/freezone/docs/1.2.4.SP2/TreeCacheAop/en/html_single/index.html#api)
>>>>>
>>>>> and it seems that it is already used for the
>>>>> FieldBasedClusteredSession but that there is an overhead there of
>>>>> creating observer for the pojo although the TreeCacheAop does the
>>>>> exact same thing for you (at least that is my understanding of
>>>>> TreeCacheAop as defined in the link above "Note that a user will
>>>>> only need to issue this call once for each POJO (think of it as
>>>>> attaching POJO to cache management). Once it is executed,
>>>>> TreeCacheAop will assign an interceptor for the pojo instance and
>>>>> its sub-objects." but I start to think that my assumption is wrong
>>>>> here... can you confirm ?)
>>>>>
>>>>
>>>> To use putObject you have to use FieldBasedClusteredSession, and
>>>> PojoCache (fka TreeCacheAop) can only add the interceptor, detect
>>>> changes to the object etc. if the attribute's class has been
>>>> bytecode enhanced by JBoss AOP. Not a default solution, since most
>>>> users will not take the steps needed to bytecode enhance their classes.
>>>>
>>>> If you use putObject and the object is not bytecode enhanced,
>>>> PojoCache has no idea if you subsequently change the object. So
>>>> you're back to the issue of needing to deal with user forgetting to
>>>> call setAttribute.
>>> Ok it's clearer now and it all makes sense :-)
>>> I guess even with JbossCache 2.x and Jboss 5.x we will need to deal
>>> with the same thing then, right ?
>>>
>>
>> Yes.
>>
>>> I was wondering if one could leverage the jboss-web.xml with new tags
>>> in it to state which are the classes he wants to be replicated. (with
>>> potentially pattern macthing)
>>> On those classes, at load time, JbossAS would add automatically the
>>> necessary Jboss cache annotation
>>> (@org.jboss.cache.pojo.annotation.Replicable) through the javassist
>>> library and the classes will be aspectized with load time weaving and
>>> thus the full features of PojoCache could be used with no extra code.
>>> But I guess the problem here is that it still add some burden on the
>>> end developer to describe things in jboss-web.xml and that could be
>>> error prone so not an ideal solution neither I guess
>>>
>>
>> If a user doesn't want to annotate their classes, they can deploy a
>> jboss-aop.xml file to get the load time weaving. Adding the facility
>> you describe in jboss-web.xml might make the syntax a bit easier, but
>> it's doable now.
>>
>>
>
>
--
Brian Stansberry
Lead, AS Clustering
JBoss, a division of Red Hat
brian.stansberry at redhat.com
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