run script on agent if the server is not available

[pedrofmp]

Hi guys,

I'm not even sure if this is feasible, but i have a remote site connected thru a cellular modem. The problem is, sometimes the modem goes down and the only way to get back the communication is rebooting it.
I was just wondering if there's a way for the agent to detect if the server is down for more than, lets say, 5 minutes and then trigger a script to reboot the modem.

server --> modem --> station running the agent

if server has no communication with agent then station run script to reboot the modem.
i've tried active agent but i cannot run an action if the agent is not available.

[Pada]

If the modem is on the same machine as your zabbix server, then you should be able to reboot the modem with a script quite easily.

First add an Zabbix agent (active) item to your "station", with a key: agent.ping

First add a trigger to your "station", with an expression like follow:

{station.yourdomain.com:agent.ping.nodata(5m)}=1

* This trigger will go off as soon as it hasn't received any data from the active agent in 5 minutes. Change 5m to be like at least 3x bigger than your agent.ping's update interval.

Now go and add the script under Administration > Media Types, and then assign that new media type to a user.

Now you can go and add an Configuration > Action, that is only triggered by that specific trigger. Have this trigger run a script (by letting it notify the user with the new media type) that reboots your modem.

I hope this is detailed enough for you.

[pedrofmp]

Hi Pada,

Thanks for your reply.
Unfortunately, the modem is attached to the remote system, not the server.
if i understand correctly, the action will be taken by the server and not the remote agent, so i guess i cant run the script on the agent if the connection is down.
I'll use cron instead.

Thanks again.

[Pada]

Yes, unfortunately the action would be taken by the Zabbix server and not by the client like you'd want in your situation.

If you run a VPN between the two sites, then you can probably modify their ifdown script to also reboot your modem. I know you can do this when you run OpenVPN on the linux machine.

If you're not using a VPN and you can ping the server from the client, then have a look at fping, because with fping you can set like an exponential backoff factor, interval between the ping attempts, etc.
fping will return with exit code of 0 when it had 1 successful ping (eg. even if it had 99% packet loss).

For example you can use the following script in a cron job that runs every minute:

#!/bin/sh
ip=172.30.30.242
fping -B 2 -r 3 -p 1000 -t 1000 $ip
if [ $? -ne 0 ]; then
        echo "Connection lost"
        # run script to reboot modem
fi

fping man pages: http://linux.die.net/man/8/fping

[pedrofmp]

I was trying to avoid scripts on cron but it seems the way to go.
Thank you very much for your help ( and for the code as well)