Monitor # of established sockets with Monit?

Question

I cannot figure out how to get Monit to monitor the number of open/established TCP/IP connections on a server so an alert can be sent when "too many" are open. Do you know how this can be setup?

*netstat | grep tcp | wc*? Sorry I am not familiar with Monit but that will give you a (moderately accurate) number to work with. — TheFiddlerWins, Sep 12 '13 at 15:01

score 1 · Accepted Answer · answered Sep 12 '13 at 17:05

here is another Solution

define following configuration monit :

check program OpenSocket with path "/bin/checkn_socket.sh"
    if status > 0 then alert
                group admin

Script : checkn_socket.sh

#!/bin/bash

Threshold=4 # Set Threshold

TotalEstSocket=$(netstat -t | awk '{/ESTABLISHED/ && n++} END{ print n }')

if (( TotalEstSocket >= Threshold ))
then
        echo >&2 "Too Many OpenSocket"
        exit $TotalEstSocket
else
        exit 0
fi

Monit Logs

[IST Sep 12 22:32:14] error    : 'OpenSocket' status failed (4) for /bin/checkn_socket.sh. Error: Too Many OpenSocket
..
[IST Sep 12 22:32:17] info     : 'OpenSocket' status succeeded
[IST Sep 12 22:32:26] error    : 'OpenSocket' status failed (4) for /bin/checkn_socket.sh. Error: Too Many OpenSocket
..
[IST Sep 12 22:32:29] error    : 'OpenSocket' status failed (4) for /bin/checkn_socket.sh. Error: Too Many OpenSocket
..
[IST Sep 12 22:32:32] error    : 'OpenSocket' status failed (4) for /bin/checkn_socket.sh. Error: Too Many OpenSocket
..
[IST Sep 12 22:32:35] info     : 'OpenSocket' status succeeded

Yes I just did this as well (see my comment above). #!/bin/sh exit $(netstat -t | grep ESTABLISHED | wc -l) ... and check program too_busy with path "/..." if status > 16384 then alert — z8000, Sep 12 '13 at 17:08

score 0 · Answer 2 · answered Sep 12 '13 at 16:48

It doesn't seem to be supported directly but I came up with a hack.

Determine the number of ESTABLISHED connections every minute and write a file with an equal number of zero bytes.

Then, setup Monit to check on file size of this zeros file. If it gets "too big" alert.

In crontab for some user:

* * * * * /bin/sh -c '/bin/dd if=/dev/zero of=/tmp/tcp_connections.monit count=$(/bin/netstat -t | /bin/grep ESTABLISHED | /usr/bin/wc -l) bs=1 >/dev/null 2>&1'

In Monit config:

check file tcp_connections with path /tmp/tcp_connections.monit
    if size > 16KB then alert

Or easier just write a script whose exit code is the number of sockets and use `check program ...` — z8000, Sep 12 '13 at 17:03

Monitor # of established sockets with Monit?

2 Answers2