I'm currently using DCRUM 12.1 and I'd like to know if there exists any metric I can use to be able to measure the effective number of TCP active sessions?
I see that I can only have idle sessions, TCP connection attempts, but I can't see anywhere a measure of TCP active connections.
Is there a way to access that specific info or not?
Thanks in advance.
AFAIK there's not such metric.
But there's also "RTT measurements" that will tell you how many sessions were opened in a given interval (however it contains closed sessions in that interval as well)
In fact, we wanted to be able monitor the web server capacity, and to be able to set an alarm if the number of TCP active sessions reaches a critical treshold to prevent users from being kicked out when the maximum is reached.
Well if you want to use that as a warning indicator you always have the "Connection Refused" alarm you could use, or the "Server not responding".
There are a couple under "TCP Errors" that can help you spot such issues.
Connection refused errors
The number of TCP errors of category:
Connection refused errors, also referred to as Session establishment errors. This category of errors applies when a server rejects a request from a client to open a TCP session. Such a situation usually happens when the server runs out of resources, either due to operating system kernel configuration or lack of memory.
Appendix D - DCRUM AlertSystemAdmin - page 83.
Ok thanks, indeed I saw those metrics, but the only "problem" is that it's too late when we do get a "connection refused alarms", I thought there was a way to be proactive with this topic, but it seems not :-s.
Thanks for your input.
It would be hard to measure against a hard number since you can have persistant connections as well as short lived ones and if you have sessions that just "die", you won't be aware that they are gone.
It's partly a problem of how sessions are terminated or in some cases not. That's why it's better to keep an eye on how the servers respond.