[jbosscache-dev] Some new Cache usage questions

[Brian Stansberry]

Isn't caching a Node dangerous, as you have no way of knowing it hasn't
been removed from the tree?  Unless you add a CacheListener just for
that.

jbosscache-dev-bounces at lists.jboss.org wrote:
> Use Cache for cache-wide operations like getRegion(), etc.
> 
> Use Node to manipulate data in the node, retrieve child nodes, etc.
> This way refs to Nodes - buckets of data storage - can be
> cached since it is these that would be most frequently used.
> 
>> It does. But then, does it mean I need to keep both the reference for
>> Cache and "parent" Node at the same time? Although Cache is a
>> wrapper, it does have some additional APIs like evict and also
>> getRegion() that doesn't exist in Node. Or what's your
>> recommendation? 
>> 
>> Actually, currently I am keeping the CacheSPI reference (and also
>> possibly NodeSPI in the future when it has life of its own) within my
>> code. Keeping the Node reference doesn't seem to make much sense to
>> me, although this can be just a pattern for the customed cache
>> provider (e.g., PojoCache). 
>> 
>> -Ben
>> 
>> -----Original Message-----
>> From: Manik Surtani [mailto:manik at jboss.org]
>> Sent: Tuesday, September 05, 2006 12:10 AM
>> To: Ben Wang
>> Cc: Bela Ban; jbosscache-dev at lists.jboss.org
>> Subject: Re: [jbosscache-dev] Some new Cache usage questions
>> 
>> 
>> On 4 Sep 2006, at 16:58, Ben Wang wrote:
>> 
>>> 1. I suspect people using JBC for session management purpose won't
>>> store the Node ref but the Cache instead. Brian can say better but
>>> for example of the http session, unless you store the root Node,
>>> otherwise caching the children Node is not that useful.
>> 
>> Node jSessionNode = Cache.getChild(Fqn.fromString("/ JSESSIONID"));
>> // this can be cached... Node sessionNode =
>> jSessionNode.getChild(Fqn.fromString (sessionId));  // this can be
>> retrieved every time... 
>> 
>> Does this help in any way?
>> 
>> 
>>> 
>>> 2. ic. Do we have explicit contract for Cache to be "root" Node
>>> only? I mean, even getRoot() is just a self pointer, it still
>>> serves the purpose, IMO.
>> 
>>  From the javadocs: "The cache is essentially a wrapper around the
>> default root Node." 
>> 
>> 
> http://labs.jboss.com/file-access/default/members/jbosscache/freezone/
>> docs/Habanero/api/org/jboss/cache/Cache.html
>> 
>> 
>>> 
>>> -Ben
>>> 
>>> -----Original Message-----
>>> From: Manik Surtani [mailto:manik at jboss.org]
>>> Sent: Monday, September 04, 2006 7:06 PM
>>> To: Ben Wang
>>> Cc: Bela Ban; jbosscache-dev at lists.jboss.org
>>> Subject: Re: [jbosscache-dev] Some new Cache usage questions
>>> 
>>> Not in your case, no.  But many other use cases will be able to
>>> cache a node and use it directly. 
>>> 
>>> I too would rather keep the API clean in this regard. Also, calling
>>> cache.getRoot() is redundant since the Cache interface is a wrapper
>>> around the root Node.  In fact, I even think we should get rid of
>>> the getRoot() method. 
>>> 
>>> Cheers,
>>> --
>>> Manik Surtani
>>> 
>>> Lead, JBoss Cache
>>> JBoss, a division of Red Hat
>>> 
>>> Email: manik at jboss.org
>>> Telephone: +44 7786 702 706
>>> MSN: manik at surtani.org
>>> Yahoo/AIM/Skype: maniksurtani
>>> 
>>> 
>>> On 1 Sep 2006, at 15:49, Ben Wang wrote:
>>> 
>>>> Thing is I only do put to specific fqn once. So caching it doesn't
>>>> buy you anything. 
>>>> 
>>>> -----Original Message-----
>>>> From: Bela Ban
>>>> Sent: Friday, September 01, 2006 10:22 PM
>>>> To: Ben Wang
>>>> Cc: jbosscache-dev at lists.jboss.org
>>>> Subject: Re: [jbosscache-dev] Some new Cache usage questions
>>>> 
>>>> My 2 cents: I'd rather keep the API clean, at the expense of folks
>>>> potentially writing wrapping code (like Ben).
>>>> 
>>>> Your code samples look a bit weird:
>>>> #1
>>>> Why do you always get the child ? Can't you get the node and cache
>>>> it, e.g. Node n=cache.getRoot().getChild(fqn);
>>>> n.containsKey(PojoInstance.KEY)
>>>> 
>>>> #2
>>>> Same as for #1: you don't need to call cache.getRoot().getChild
>>>> (fqn) all the time, for example in a loop, simply cache it
>>>> 
>>>> 
>>>> Ben Wang wrote:
>>>>> Manik,
>>>>> 
>>>>> While trying to use the new API in PojoCache, I have found that I
>>>>> need to: 
>>>>> 
>>>>> 1. To check if a attribute exist, I need to do:
>>>>> cache_.getRoot().getChild(fqn_).getData().values().contains
>>>>> (PojoInstance.KEY) 
>>>>> 
>>>>> 2. And then, I need to do a lot of cache_.getRoot().getChild
>>>>> (fqn).put(map) 
>>>>> 
>>>>> So looks like I need to write a wrapper layer just to provide
>>>>> straight api for: 
>>>>> 
>>>>> Cache_.exists(fqn, key)
>>>>> And
>>>>> Cache_.put(fqn, map)
>>>>> 
>>>>> If this is rare case, then I will bite the bullet. But if it is a
>>>>> common one, then that really begs the question whether we should
>>>>> provide additional apis or not?
>>>> 
>>>> --
>>>> Bela Ban
>>>> Lead JGroups / Manager JBoss Clustering Group JBoss - a division
>>>> of Red Hat 
>>>> 
>>>> _______________________________________________
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>>>> jbosscache-dev at lists.jboss.org
>>>> https://lists.jboss.org/mailman/listinfo/jbosscache-dev
>>> 
>> 
> 
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Brian Stansberry
Lead, AS Clustering
JBoss, a division of Red Hat
Ph: 510-396-3864
skype: bstansberry