icinga2/doc/6.06-dependencies.md

Dependencies

Icinga 2 uses host and service Dependency objects either directly defined or as inline definition as dependencies dictionary. The parent_host and parent_service attributes are mandatory, child_host and child_service attributes are obsolete within inline definitions in an existing service object or service inline definition.

A service can depend on a host, and vice versa. A service has an implicit dependency (parent) to its host. A host to host dependency acts implicit as host parent relation. When dependencies are calculated, not only the immediate parent is taken into account but all parents are inherited.

A common scenario is the Icinga 2 server behind a router. Checking internet access by pinging the Google DNS server google-dns is a common method, but will fail in case the dsl-router host is down. Therefore the example below defines a host dependency which acts implicit as parent relation too.

Furthermore the host may be reachable but ping probes are dropped by the router's firewall. In case the dsl-router``ping4 service check fails, all further checks for the ping4 service on host google-dns service should be suppressed. This is achieved by setting the disable_checks attribute to true.

object Host "dsl-router" {
  vars.address = "192.168.1.1"
}

object Host "google-dns" {
  vars.address = "8.8.8.8"
}

apply Service "ping4" {
  import "generic-service"

  check_command = "ping4"

  assign where host.vars.address
}

apply Dependency "internet" {
  parent_host = "dsl-router"
  disable_checks = true

  assign where host.name != "dsl-router"
}