Re: Cache Issue in distributed environment

[Armin Waibel]

Hi Cedric,

Cédric Talon wrote:
Hi, I am new on this mailing list and so it is my first message.


welcome to this list!


I am working on a project which is using OJB in a distributed
environment. The distributed issue is my problem ! I have read there
are important points to respect in this case.

The first one is to use Sequence Manager. It's ok for me.

The second one is the locking issue. I am using the
LockManagerRemoteImpl. So I think it is ok.

Do you use the ODMG-api implementation?
http://db.apache.org/ojb/docu/guides/odmg-guide.html
Only this implementation supports pessimistic locking by default.
The PB-api
http://db.apache.org/ojb/docu/guides/pb-guide.html
only supports optimistic locking by default.
http://db.apache.org/ojb/docu/guides/lockmanager.html

For best performance I would recommend to use optimistic locking (needs 
a 'version' column in the database table) for all concurrent modified 
persistence objects.


The last point is the cache issue. And this is the subject of this
mail. Currently I am using ObjectCacheDefaultImpl. I know it is not
suitable for distributed environment. That's why I'd like to use
distributed cache.

Here you can find a short description how the cache works
http://www.mail-archive.com/ojb-user@db.apache.org/msg16075.html
My estimation is that in most cases OJB will benefit more from a fast 
DB/DB-cache/network (in combination with a session cache) than from a 
distributed cache (except you do a lot of "get object by identity" stuff).
I would recommend to run some load tests with/without distributed cache.


I have heard about OS Cache but it requires a multicast network. It
is not possible in my case. I have heard about JCS too. Has anybody
ever used it? 

Sorry, I don't have experience in this.

I don't find information to configure it with OJB. Can
anybody help me ?

If you use OJB 1.0.5rc1 change the object-cache element within your 
jdbc-connection-descriptor to

one global cache region:
<object-cache class="JCS">
</object-cache>

a cache region for each class:
<object-cache class="JCSPerClass">
</object-cache>

For version 1.0.4 specifiy the full qualified class name (e.g. 
org.apache.ojb.broker.cache.ObjectCacheJCSPerClassImpl).

You can configure the JCS cache via the cache.ccf properties file.

regards,
Armin

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