There is a variety of questions answered in the community support channels. Sometimes we just hack away fancy solutions directly inside the Icinga 2 DSL. Some of these examples are collected inside the documentation, others are posted on the community channels. Or they are just provided in hands-on workshops at customers waiting for sharing their stories to the world :)

This time there was the this question over at monitoring-portal.org – a host object collects a bunch of passive services and should calculate its overall state and output from the (worst) state of all referenced services.

Sounds easy. You could go for business process check returning the calculated value. Or you stick with many of the Icinga 2 configuration language features and put them altogether.

For a small test environment, I’ve generated 5 services using the random check (replace that with your real world scenario).

 

for (j in range(5)) {
  object Service "host-servicestatus-" + j {
    check_command = "random"
    check_interval = 30s
    retry_interval = 15s
    host_name = "host-servicestatus"
  }
}

The host object called “host-servicestatus” just uses the “dummy” check command provided by the ITL. This check command expects two custom attributes: “dummy_state” and “dummy_text”.

Now for the fun part – implement two lambda functions for these custom attributes using the available methods.

  vars.dummy_state = {{ ... }}
  vars.dummy_text = {{ ... }}

We want to calculate the worst state for all services on this specific host. Therefore we’ll use a temporary variable to save and update the worst state.

    var worst_state = 0

At first glance we want to selectively iterate over all service objects using the object accessor method “get_objects” with “Service” type. Then we’ll compare the service “host_name” attribute to the local scope (our host and its name). We’ll just skip all services not matching.

    for (s in get_objects(Service)) {
      if (s.host_name != host.name) {
        continue; //skip all services not referencing this host object
      }

The local to the loop variable “s” provides us with access to the all attributes for the current service object. Check whether its state is greater than 0 (not OK) and greater than the previously collected worst state. If so, store it in the local variable “worst_state”.

      if (s.state > 0 && s.state > worst_state) {
        worst_state = s.state
      }
    }

After the loop is finished, just return the “worst_state” variable for this function.

    return worst_state

In terms of generating an additional output text with all service names and their state, we’re using the same loop and conditional checking as above. Except we are using a temporary variable as an array of strings like this:

    var output = []

Inside the loop we’ll add the current service name and its state as string element to the “output” array.

      output.add(s.name + ": " + s.state)

Once the loop is finished, join the array elements with the separator “, ” concatenate the final output string and return it.

    return "Service summary: " + output.join(", ")

We could also concatenate the string as is but then we would need to think about the last loop run not adding the “,” character. The array join method just simplifies that step.

icinga2_host_servicestatus_web2The final solution works like a charm :-) If you say – hey I am not a coder – it helps to know Javascript, or Python or something similar of course. After all it is a pretty neat solution for helping a community member :)

 

object Host "host-servicestatus" {
  check_command = "dummy"

  vars.dummy_state = {{
    var worst_state = 0
    for (s in get_objects(Service)) {
      if (s.host_name != host.name) {
        continue; //skip all services not referencing this host object
      }

      if (s.state > 0 && s.state > worst_state) {
        worst_state = s.state
      }
    }

    return worst_state
  }}

  vars.dummy_text = {{
    var output = []

    for (s in get_objects(Service)) {
      if (s.host_name != host.name) {
        continue; //skip all services not referencing this host object
      }

      output.add(s.name + ": " + s.state)
    }

    return "Service summary: " + output.join(", ")
  }}
}