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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