Hi Bart,
We have this multi-tier application which offers financial services to organizations
thereby enabling them to offer a custom visualization of the effect of (a financial)
product(s) based on the customer's own unique data.
That out of the way, the system on the server side is built on the EJB 1.1 standard.
EJB Server: Borland AppServer 4.0.2
OS's: Windows NT Server 4.0, Linux
JDK 1.2.2 Production
Database: MS SQL Server 7.0
JDBC Driver: WebLogic's MSSQLServer Driver v4.7
The server side is 99% CMP (as opposed to BMP). The number of Entity Beans classes are
approximately 150 and the same number of stateless session beans which total upto
around 300 enterprise beans. The stateless beans 'wrap' the entity beans providing
business logic, checks, transaction support etc. Clients never access the entity
beans. The basic architecture is almost the same as Ed Roman's document on designing
EJB's (theserverside.com) with the use of value objects, session 'wrap' entity beans
etc.
As to the stability of the system, I would go as far as to say "extremely stable". I
am quite sceptical about BMP as i have seen code that looks worse than spagetti
through a grinder. But this could be advantageous in certain cases, though the idea is
to keep this to a bare minimum. Almost 100% CMP can be achieved through the Entity
Bean relationships (DB master detail), DB views etc. We have had this system running
for over 8 months now and are quite satisfied with the performance. (Runs on a dual
xeon PIII 600 Mhz with 512kb cache and 512mb ram) The longest we've had the server
side running is for a period of 1-1/2 months without a server shutdown/reboot/crash.
Performance under heavy loads (simulated 1000's of web users and 100's of Windows
Client users) is good and with clustering increases even further. The number of Entity
Bean instances (of these 150 classes that map to the same number of tables in the DB)
we have recorded is around 10,000 at normal usage.
Also the Borland AppServer provides an easy setup of failovers and clustering, and
normally we recommend having another machine for the server as load balancer and/or
failover. Much of this is upto the customer depending on their need of availability
and scalability of the application.
If you are interested, a little write up of a case study in which we appear which is
due to appear in a book by author Lisa Lindgren sometime this month and is available
at http://krish4u.htmlplanet.com as a pdf document.
Questions are welcome.
Regards,
Krishnan
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