Howot debug network connections from JVM?

[Stefan Mayr <st...@mayr-stefan.de>]

Good morning,

I could need some ideas how to debug a very specific network problem. It 
is not directly Tomcat related (more JVM) but maybe you have some pointers.

The situation: We have an application running in Tomcat on two different 
servers (TomcatA, TomcatB). Both are doing HTTP calls to an application 
in a different network (RemoteApp).
In the middle of the night the RemoteApp does not respond to our HTTP 
calls an we get (expected) timeouts for some minutes. This is okay so 
far. After RemoteApp has some CPU cycles left to answer our requests 
again, it becomes strange:
one of the two Tomcats can communicate with RemoteApp. The other can not 
(still getting timeouts). This does not happen every night and it is not 
fixed to TomcatA or TomcatB. Last night I used tcpdump and I don't know 
how to interpret it:

TomcatA connects to RemoteApp (SYN, SYN/ACK, ACK) and immediately closes 
the connection (FIN/ACK) in no time (<1ms). This does not look like a 
timeout as reported in the logfiles and there is no HTTP request on the 
wire.

Any ideas howto narrow this down? How can I find out who closes the 
connection? Candidates are the webapp, the Tomcat/JVM-Process, OS-Limits 
or the OS (Linux) itself?
As this only happens in production debugging is "not easy".

Any ideas welcome,

    Stefan

---------------------------------------------------------------------
To unsubscribe, e-mail: users-unsubscribe@tomcat.apache.org
For additional commands, e-mail: users-help@tomcat.apache.org