For light duty shared data service (such as Cache Manager), I liked the idea of using
Global Session as suggested by
Brendan. i.e create a singleton instance of Cache Manger class during init of the
project and store its reference in Global Sessions.
Any clients, in our case Stateless EJB, can then obtain the handle to Cache Manager
object from Global Session.
But EJB's could possibly run in multiple JVM's. Is there any issue about obtaining
handle to a object reference
via GlobalSession when that object (Cache manager) could potentially be in a
different JVM?
Thanks for your input.
Raj
"Johnston, Brendan " <[EMAIL PROTECTED]> wrote:
>I have implemented a number of small caches which have not been generalized.>They
>Cache small numbers of codes etc, which are assumed to be constant
>during the execution of the program.
>
>I chose to implement them in data objects (usually the one which fills the
>cache).
>This means that the cache is duplicated for each thread.
>This removes any need to waste brain time thinking about synchronization and
>makes the cache very fast.
>However the cost is extra time filling the cache and extra memory.
>
>If you want to share objects across sessions you should not use session
>beans, Entity beans are for this.
>
>Since ND runs in multiple processes on different physical machines a global
>cache seems problematic.
>
>Here are some ideas:
>
>1. GlobalSessionObjects might help you
>2. If there is a lot of data and you want to access it from multiple ND
>processes, put the cache in a database
>
>Brendan Johnston
>TeamND
>
>
> -----Original Message-----
> From: [EMAIL PROTECTED] [SMTP:[EMAIL PROTECTED]]
> Sent: Friday, April 16, 1999 6:53 AM
> To: [EMAIL PROTECTED]
> Subject: Re: [ND] Implementing a Cache Manager
>
> Curt,
>
> Thanks for your input.
>
> My requirement is to share the data managed by the Cache Manager
>component across multiple sessions.
> If possible, I would like to implement with EJB (Statefull?) but
>not quite sure if EJB would be a right model to implement
> a shared data service. For one, I have to ensure that there is only
>one instance of this bean. Otherwise, cached data will
> splitter across multiple instances of EJB (which may be running in
>different JVM)...and then I have to deal with locating right
> instance of bean etc.
>
> You mentioned about data caching in ND5. Where and how is this
>being done? In JDBC service?
>
> Is PAC more appropriate model than EJB in ND5 for some thing like
>this?
>
> Raj
>
>
>
> Curt Springer <[EMAIL PROTECTED]> wrote:
> >First off, you should look at the data caching feature in ND5 to
>see if>that might do something for you.
> >
> >Anyhow, I've got some stuff that caches rows, on a session basis.
> >Question: are you trying to cache data for use in one session or
>across
> >multiple sessions?
> >
> >If for one session, I would put the data into a session object. In
>each
> >page get the session object in onBeforeLoad or button/href web
>events, put
> >it back at the end of processing. I keep rows from up to 30 tables
>in
> >memory on this basis.
> >
> >At one point, I had a singleton class, and it killed performance.
>I found
> >that it worked to have one object of the class owned by each page
>class,
> >since much of ND's object instantiation model is driven at the page
>level.
> >
> >You should also look at EJB in ND5. That would be a cleaner
>implementation
> >than anything available in ND4, except maybe a PAC.
> >
> >-- Curt Springer, Team ND
> >
> >At 04:08 PM 4/15/99 -0800, [EMAIL PROTECTED] wrote:
> >>In our architecture, we have a Cache Manager component which
>caches the
> >data (in memory) to
> >>reduce trips to the DB. Cache Manager is a singleton, i.e. there
>is only
> >one instance of Cache Manager.
> >>What is the best way to implement the Cache Manager in ND so that
>the
> >cached data
> >>is accessible to other services?
> >>
> >>Thanks...
> >>
> >>Raj
> >>
>
>>>_________________________________________________________________________
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>
>
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