Nagios Calling
Out of the box, Nagios can only alert you by email when a service fails,
but these email messages can be easily overlooked. A call is more
sustainable.
It's difficult to ignore a ringing phone, so it makes sense to
teach Nagios how to make phone calls. You can do this with a combination
of Nagios [1] and Asterisk [2].
Configuring Asterisk is less than trivial, and setting up a complete
PBX just for monitoring is slightly over the top; however, you can sign
up for a SIP (Session Initiation Protocol) account for not too much
money, add a CLI SIP client and a simple shell script, and do the same
thing with less overhead (Figure 1).
Figure 1: As you can see, the command that picks up the message – here, an email script – works.
A Matching SIP Client
The process for the CLI SIP client is slightly more complex. Most VoIP clients are designed for the desktop and cannot be scripted at all, or at least not very well. Of the available clients, PJSUA [3] turns out to be the best choice. PJSUA is the PJSIP reference implementation, and it comprises a function library for SIP, RTP, STUN, and some other VoIP-related protocols.Unfortunately, there are no PJSUA packages, which means building from the source code – although this is done easily enough. You can do the following to pick up the PJSIP/PJSUA source code:
wget http://www.pjsip.org/release/2.0./pjproject-2.0.1.tar.bz2Next, go to the directory where you unpacked the tarred and zipped file and type:
./configure make dep makeYou will now have a file starting with
pjsua in your pjsip-apps/bin
directory. This is the SIP client. You can copy it to anywhere you like
on your system and make it executable. Next, you need a configuration
file for the client; you define the access credentials for the SIP
provider here.To define the access credentials, create a text file with the content from Listing 1. You need to modify the content to match your own SIP provider, of course; this might be difficult in some cases because providers tend to use their own designations for
id and realm. If in doubt, you can call your provider's hotline. --null-audio tells the server not use any audio output and thus avoids outputting calls via the computer's loudspeakers.
Listing 1
Provider Data
--null-audio --registrar sip:sipgate.de --realm=sipgate.de --id sip:username@sipgate.de --username sipgateusername --password sipgatepasswort
The Call Script
Next, you need a script that Nagios can call when the need arises (Listing 2). This script also ensures that messages do not interfere with one another. If Nagios needs to make two calls in quick succession, the script ensures that the first call terminates before the second one begins. Otherwise, the client would refuse to cooperate because the line was occupied, and the second message would be lost.
Listing 2
Call Script
01 #! /bin/bash 02 03 EXPECT=/usr/bin/expect 04 PJSUA=/opt/pjsua 05 PJSUACONFIG=/opt/pjsua.conf 06 SOUNDFILE=/tmp/alert.wav 07 TEXT2WAVE=/usr/bin/text2wave 08 DURATION=20 09 NUMBER=01234567890 10 MESSAGE="Monitoring Alert" 11 12 # Setting a lock file 13 # We can't make more than one call 14 # at a time, because pjsua blocks the port 15 # so we have to make sure that nobody else tries to call 16 # If there is already a call we have to wait. 17 18 locked=false 19 while [[ $locked == false ]]; do 20 if [[ ! -f /tmp/caller.lock ]]; then 21 touch /tmp/caller.lock 22 locked=true 23 else 24 sleep 5 25 fi 26 done 27 28 # Generating the message 29 $TEXT2WAVE -o $SOUNDFILE -f 8000 << EOF 30 $MESSAGE 31 EOF 32 33 # Making the call it self. 34 # Expect will start pjsua and work with 35 # it so that it will end it self automatically 36 37 $EXPECT << EOF 38 spawn $PJSUA --config-file $PJSUACONFIG [UCC:z-inhbullet][/UCC] --play-file $SOUNDFILE --auto-play --duration $DURATION --max-calls 1 sip:$NUMBER@sipgate.de 39 expect "VAD re-enabled" 40 sleep $DURATION 41 send "q\n" 42 EOF 43 44 # Cleaning up 45 rm $SOUNDFILE 46 47 # Removing the lock file 48 rm /tmp/caller.lock
expect, to control pjsua, and text2wave, to create a WAV from a line of text. The text2wave tool is part of Festival, a program for voice synthesis [4]. Both packages can be installed via your package manager. Next, you should make the script in Listing 2 executable.In the listing, you should set the value of
NUMBER to the phone number you want Nagios to call. MESSAGE
contains what you want the call recipient to hear. If you prefer not to
hard wire the phone number into the script, you can pass the number in
to Nagios. DURATION lets you configure the maximum duration
for the call. If nobody picks up the phone within this time, the script
hangs up. If somebody takes the call, the script plays the message in a
loop. You may need to modify the last argument to match your own SIP
provider in the line starting with spawn.On My Command
Finally, you need to reconfigure Nagios to call the script in case of an alert. To do so, start by defining a new command. If you are using Ubuntu 12.04 and Nagios3, you will find the matching file in/etc/nagios3/resource.cfg. For other distributions, the path might differ slightly. Next, insert the content from Listing 3.
Listing 3
resource.cfg
01 # Additional commands, so that nagios can call the sysadmins
02 define command {
03 command_name notify-host-by-phone
04 command_line /opt/pjsua_wrapper
05 }
06
07 define command {
08 command_name notify-service-by-phone
09 command_line /opt/pjsua_wrapper
10 }
/opt/pjsua_wrapper is the path to the script. You may also need to modify this. Then, you simply need to modify the contact definition for the administrator in Nagios. The configuration typically looks like this:define contact {
...
service_notification_commands notify-service-by-email
host_notification_commands notify-service-by-email
...
}
Simply add the new commands to the two parameters:define contact {
...
service_notification_commands
notify-service-by-email,notify-host-
by-phone host_notification_commands
notify-service-by-email,
notify-service-by-phone
...
}
Finally, you can restart Nagios and wait for calls to come in.
Infos
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