Add apply_prefix argument to service object to fix issue #227

[fredrik-eriksson]

Hi,

Although I personally would prefer that the default should be to add the prefix to all apply loops I understand that some may think otherwise. Also, that would be a breaking change.

With this commit I simply add an apply_prefix argument that allows you to optionally add a service prefix to be able to add services that otherwise would result in name collisions. By default apply_prefix is set to undef to preserve the current module behavior.

[bobapple]

The same can be achieved with a syntax like:

apply Service for (interface_name => interface_config in host.vars.interfaces) {
  import "generic-service"
  check_command = "iftraffic"
  display_name = "IF-" + interface_name

  [...]
}

What are the benefits of using the apply_prefix instead?

[fredrik-eriksson]

No, setting display_name is not the same thing. As I described in issue #227, without the prefix you cannot have multiple services looping over the same dict. Consider a host where the dict vars.network.interfaces look like this:

vars.network.interfaces = {
  lo0 = {
    address = "127.0.0.1"
    addressv6 = "::1"
  }
}

Then try to apply the following services:

apply Service for (interface => opts in host.vars.network.interfaces) to Host {
  vars.ping_address = "opts.address"
  vars.ping_cpl = getvar(host.vars.ping_cpl, 40) 
  check_command = "ping4"
  display_name = "ping4_interface_" + interface
  assign where "opts.address"
}

apply Service for (interface => opts in host.vars.network.interfaces) to Host {
  vars.ping_address = "opts.addressv6"
  vars.ping_cpl = getvar(host.vars.ping_cpl, 40) 
  check_command = "ping6"
  display_name = "ping6_interface_" + interface
  assign where "opts.addressv6"
}

A configtest will then fail with this message:

critical/config: Error: An object with type 'Service' and name 'localhost!lo0' already exists (in /usr/local/etc/icinga2/conf.d/services_ping.conf: 21:1-21:77), new declaration: in /usr/local/etc/icinga2/conf.d/services_ping.conf: 53:1-53:77

It looks to me that icinga2 converts all apply-rules to "real" objects; but those objects still needs to have unique names. If more than one service loops over the interface list on a host (as here with ipv4 and ipv6 services) both services will get the interface name as service name, causing a naming collision. Setting display_name does not solve that issue.

[dnsmichi]

I think this will add an enhancement to the current apply logic. I'm a heavy user of that functionality when writing apply-for rules. A definitive 👍 from me :)

[lbetz]

I did it on a different way, maybe you like it too.

Branch: enhancement/Add-apply_prefix-argument-to-service-object-to-fix-issue-228

Use parameter prefix (boolean) to get the object_name as prefix.

[fredrik-eriksson]

Works for me :)

[geor-g]

Could this be merged?