[DUG] DataSnap/Midas App Server Error

[Dave Jollie]

You could create a logging class. In each important procedure on the
server's RDM, create a logging instance at the beginning of the
procedure. Wrap the procedure in a try finally, freeing the logging
object at the end of the procedure. Within the try..finally, have a
try...except, catching any exception and feeding it to the logging
object. The logging object records to file, the start and end times of
the procedure, any exceptions, etc. In this way you'll find procedures
that are bottlenecks, procedures that throw exceptions, and any that
never return, for whatever reason.

 

To reduce the volume of your log file, on freeing of the logging object,
you could do some tests - if no exceptions were recorded in the
procedure and it didn't take too long to execute, then don't write any
info to file - only write to file for exceptions or very long times.
However, then you'd miss any procedure which never returns. For this
you'd need to log a procedure name and time stamp on create of the
logging object.

 

You could have an app server switch to turn logging on and off, so that
it's not going all the time, but only when indicated from the app server
GUI.

 

This may help you find something...

 

Dave

 

________________________________

From: delphi-bounces at ns3.123.co.nz [mailto:delphi-bounces at ns3.123.co.nz]
On Behalf Of Stacey Verner
Sent: Friday, 2 September 2005 9:48 a.m.
To: NZ Borland Developers Group - Delphi List
Subject: [DUG] DataSnap/Midas App Server Error

 

We have an DataSnap/Midas app server which fails randomly.

 

We can't make it happen no matter how hard we try, but it happens fairly
regularly on our production machine.

 

A little bit of info on the app and app server:

*	The applicaiton is a normal database application.
*	The application also needs to get information from a settings
(metadata) database such as:

	*	Which databases they have access to
	*	What permissions they have on the database etc

*	Instead of connecting directly to the settings database we use
the app server which shares one database connection between all clients.

	*	This means that there is one database connection for
each application instead of 2 which reduces licencing costs

*	We use the borland socket server and a socket connection to
connect to the app server.

	*	When we used a normal DCOM connection each client got
its own copy of the app server, so the settings database connection is
not shared and in effect each application had two connections to the
database.

Sometimes the app server locks up and the clients can't connect.

 

We have a work around that will try app servers on other machines if
this fails which works OK, but if it never gets a connection the all
sorts of odd things happen.

 

Firstly, does anyone have any thoughts on this. Debug ideas etc?

Secondly, when the connection to the app server fails it takes forever
(minutes) to return no matter what I set the socket connection timeout
to.

 

Thanks

 

Stacey

 

Stacey Verner             Ph:   +64-9-4154790
Software Developer        Fax:  +64-9-4154791
                          DDI:  +64-9-4154797
CJN Technologies Ltd.     Email: stacey at cjntech.co.nz
<mailto:stacey at cjntech.co.nz> 
PO Box 302-278, North Harbour, Auckland 1330, New Zealand
12 Piermark Drive, North Harbour, Auckland, New Zealand
Visit our website at http://www.cjntech.co.nz/
<http://www.cjntech.co.nz/>  

 

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