[DUG] DataSnap/Midas App Server Error

[Robert Wilson]

Hi Stacey

We are experiencing the same issues with a similar multi-tiered system 
using datasnap/midas and were actually just discussing this issue when 
these postings came through. 
Until now we have been using e-mail messages as a means of trying to 
locate problems, but obviously have to limit the number of messages sent 
so it is not always catching the issues. We were just kicking around the 
same basic idea that Dave Jollie replied with and think that this would be 
the best solution, we curently have the Server app with the ability to run 
in debug mode "where messages are sent" or standard mode " no messages". 
It is now just a matter of finding the actual time to retro fit to 
existing code..
But will certainly let you know if we find anything obvious...

Cheers
Robert Wilson





"Stacey Verner" <stacey at cjntech.co.nz>
Sent by: delphi-bounces at ns3.123.co.nz
02/09/2005 09:48 a.m.
Please respond to NZ Borland Developers Group - Delphi List

 
        To:     "NZ Borland Developers Group - Delphi List" <delphi at ns3.123.co.nz>
        cc: 
        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
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/ 
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