Service dependency on host? Here's my working solution

[Toussaint OTTAVI]

(Sorry for 'test', seems that my previous message didn't go through.)

Charlie Reddington wrote :
> I've seen the docs about having services dependent on services, and
> hosts dependent on hosts. But how about services, dependent on hosts.
> Do I just use hosts instead of services in the config?

Hi Charlie,

I had the same problem. I read a lot of topics, but I didn't find 
anything. It seems there's no way to do what we would like to do : 
services dependant on hosts, ie do not try to check all the services if 
the host is down. I must say I don't really understand the actual 
"logic" of nagios, but for now, this seems to be 'by design'.

Anyway, the "magic" of nagios applies : if it does not do what you want, 
then you just have to do it yourself.

Here's what I did, and it seems to work fine.
- activate 'event handlers' on host. This will run a nagios command each 
time a host status changes
- set up this command to run an external script (called 'disable service 
checks')
- this script will send back to nagios an 'external command' to enable 
or disable all the service checks for that host
- as there is only one handler for any state change (UP or DOWN), the 
script has to check the actual status : if host DOWN then disable 
service checks, if host UP then enable service checks

Now, let's do that :

In hosts or hosts template :
    event_handler_enabled  1  
    event_handler disable-service-checks

In your commands file:
  # event handler to disable service checks when host is down
  define command {
    command_name disable-service-checks
    command_line $USER1$/eventhandlers/disable_service_checks 
$HOSTSTATE$ $STATETYPE$ $HOSTATTEMPT$ $HOSTNAME       
    }

Then, put the following script in your plugins/eventhandler/ 
subdirectory, with name 'disable_service_checks' and execution flag :

#!/bin/sh
#
# Enable / Disable service checks after a state change of the host
# Arguments received are : $SHOSTATE$ $STATETYPE$ $HOSTATTEMPT$ $HOSTNAME
#
# by Toussaint OTTAVI, t.ottavi at medi.fr
#

CommandFile="/var/spool/nagios/nagios.cmd"
LogFile="/var/log/nagios/disable_service_checks.log"

# get the current date/time in seconds since UNIX epoch
datetime=`date +%s`

# send debug information to logfile
/usr/bin/printf "Event Handler called with Hostname:%s State:%s Type:%s 
Attempts:%s\n" $4 $1 $2 $3 >> $LogFile

# Check the $HOSTSTATE$
case "$1" in
UP)
    # Host is UP, re-enable service checks
  /usr/bin/printf "[%i] ENABLE_HOST_SVC_CHECKS;%s \n" $datetime $4 >> 
$CommandFile
    ;;
UNREACHABLE)
    # Host is UNREACHABLE, disable service checks
    /usr/bin/printf "[%i] DISABLE_HOST_SVC_CHECKS;%s \n" $datetime $4 >> 
$CommandFile
    ;;   
DOWN)
    # Host is DOWN, disable service checks
  /usr/bin/printf "[%i] DISABLE_HOST_SVC_CHECKS;%s \n" $datetime $4 >> 
$CommandFile
  ;;
esac
exit 0


Notes :
- This is early beta, I did it yesyerday evening, not sure it works 
100%, please feel free to provide feedback
- all paths are for installation on OpenSuse. You may have to 
check/change some things.
- in case of problems, first try to run the script by hand : 
'disable_service_checks DOWN HARD 1 NAME_OF_MY_HOST', then see what 
happens in Nagios
- to see if the handler really triggers, have a look at the logfile : 
/var/log/nagios/disable_service_checks.log
- external commands must be activated in nagios.cfg
- host names must not contain spaces. Maybe some scripting specialist 
could improve it...
- the $STATETYPE$ variable should return a state 'SOFT' or 'HARD', which 
would allow to improve the script (only do the action if the state 
change is HARD). But for an unknown reason, Nagios does not send this 
value, so we can not process it. Any idea ?


Enjoy Nagios Magic, I really love this tool, and hope this helps.

Kind regards,
-- 

*Toussaint OTTAVI*

*MEDI INFORMATIQUE*
*Tel :* 04 95 20 10 03
*Gsm :* 06 10 28 41 72
*Mail:* t.ottavi at medi.fr

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