nsca

The nsca target is used to submit passive Nagios/Icinga checks to an NSCA daemon.

Consider the following Icinga service description which configures a passive service:

define service{
        use                    generic-service
        host_name              localhost
        service_description    Current temp via MQTT
        active_checks_enabled  0
        passive_checks_enabled 1
        check_freshness         0
        check_command          check_dummy!1
        }

with the following target definition in mqttwarn.py

[config:nsca]
nsca_host = '172.16.153.112'
targets = {
   #              Nagios host_name,     Nagios service_description,
   'temp'    :  [ 'localhost',          'Current temp via MQTT' ],
  }

[arduino/temp]
targets = nsca:temp
; OK = 0, WARNING = 1, CRITICAL = 2, UNKNOWN = 3
priority = check_temperature()
format = Current temperature: {temp}C

Also, consider the following PUB via MQTT:

mosquitto_pub -t arduino/temp -m '{"temp": 20}'

Using a transformation function for priority to decide on the status to be sent to Nagios/Icinga, we obtain the following:

Topic option	M/O	Description
priority	O	Nagios/Icinga status. (dflt: 0)

The transformation function I've defined as follows:

def check_temperature(data):
    '''Calculate Nagios/Icinga warning status'''
    OK = 0
    WARNING = 1
    CRITICAL = 2
    UNKNOWN = 3
    if type(data) == dict:
        if 'temp' in data:
            temp = int(data['temp'])
            if temp < 20:
                return OK
            if temp < 25:
                return WARNING
            return CRITICAL

    return UNKNOWN

Requires:

• pynsca, but you don't have to install that; it suffices if you drop pynsca.py alongside mqttwarn.py (i.e. in the same directory)