What information can I gather from netstat listen queues?
Looking at the man page I can see that using "-L" in netstat it shows me the size of listen queues.
It tells me information about each column:
- 1st number of unaccepted connections
- 2nd number of unaccepted incomplete connections
- 3rd number of maximum queued connections
I notice that whenever the 1st column tends to increment higher, my application tends to become less responsive and Nagios checks for open socket connections start to fail.
Is it typical/expected to have a non-zero number of unaccepted TCP connections? Or is this an indication of an application problem?
Example (with $port being an actual port number):
netstat -La | grep $port tcp4 22/0/128 *.$port
Typically when the application is responsive the output looks like:
tcp4 0/0/128 *.$port