Target labels in probe options

[manugarg]

Copied from google/cloudprober#652, originally filed by @xenofree.

Hi,

Is it possible or will it be possible to configure probe option through file_target like this ?

resource {
  name: "10.x.x.x"
  labels {
     key: "hostname"
     value: "xxxxxxxx"
  }
  labels {
     key: "query_type"
     value: A
  }
  labels {
     key: "resolved_domain"
     value: "xxx.xxxxxx.com"
  }
}

probe {
  name: "dns"
  type: DNS
  targets {
    file_targets {
      file_path: "/data/cloudprober/config.d/dns/targets.yml"
      re_eval_sec: 60
    }
  }
  additional_label {
      key: "hostname"
      value: "@target.label.hostname@"
  }
  additional_label {
      key: "resolved_domain"
      value: "@target.label.resolved_domain@"
  }
  dns_probe {
    query_type: @target.label.query_type@
    resolved_domain: "@target.label.resolved_domain@"
  }
  interval_msec: 60000  # 60s
  timeout_msec: 10000   # 10s
}

[manugarg]

My comment:

It's going to be hard to implement a generic label replacement mechanism.

The way it works in HTTP probe is:

If "relative_url" or "host" is not defined in the probe config, and target has these labels, it automatically uses these labels.
We can do something similar for DNS probe.

[dalvizu]

If "relative_url" or "host" is not defined in the probe config

Correction - it looks like fqdn is the label which the HTTP probe inspects. Additionally the required 'name' field of the target will be used if both the probe and the fqdn label on the target are absent.

cloudprober/probes/http/request.go

Lines 60 to 69 in 75b20eb

	func hostHeaderForTarget(target endpoint.Endpoint, probeHostHeader string, port int) string {
	if probeHostHeader != "" {
	return probeHostHeader
	}
	if target.Labels["fqdn"] != "" {
	return hostWithPort(target.Labels["fqdn"], port)
	}
	return hostWithPort(target.Name, port)

e.g

    resource { 
      name: "google_homepage"
      labels { 
        key: "fqdn"
        value: "www.google.com"
      }
    }