config

Overview ¶

Package config provides parser for cloudprober configs.

Example Usage:

c, err := config.ParseTemplate(config, sysvars.SysVars())

ParseTemplate processes a config file as a Go text template using the provided variable map (usually GCP metadata variables) and some predefined macros.

Macros ¶

Cloudprober configs support some macros to make configs construction easier:

env
	Get the value of an environment variable.

	Example:

	probe {
	  name: "dns_google_jp"
	  type: DNS
	  targets {
	    host_names: "1.1.1.1"
	  }
	  dns_probe {
	    resolved_domain: "{{env "TEST_DOM"}}"
	  }
	}

	# Then run cloudprober as:
	TEST_DOM=google.co.jp ./cloudprober --config_file=cloudprober.cfg

gceCustomMetadata
 	Get value of a GCE custom metadata key. It first looks for the given key in
	the instance's custom metadata and if it is not found there, it looks for it
	in the project's custom metaata.

	# Get load balancer IP from metadata.
	probe {
	  name: "http_lb"
	  type: HTTP
	  targets {
	    host_names: "{{gceCustomMetadata "lb_ip"}}"
	  }
	}

extractSubstring
	Extract substring from a string using regex. Example use in config:

	# Sharded VM-to-VM connectivity checks over internal IP
	# Instance name format: ig-<zone>-<shard>-<random-characters>, e.g. ig-asia-east1-a-00-ftx1
	{{$shard := .instance | extractSubstring "[^-]+-[^-]+-[^-]+-[^-]+-([^-]+)-.*" 1}}
	probe {
	  name: "vm-to-vm-{{$shard}}"
	  type: PING
	  targets {
	    gce_targets {
	      instances {}
	    }
	    regex: "{{$targets}}"
	  }
	  run_on: "{{$run_on}}"
	}

mkMap
	Returns a map built from the arguments. It's useful as Go templates take only
	one argument. With this function, we can create a map of multiple values and
	pass it to a template. Example use in config:

	{{define "probeTmpl"}}
	probe {
	  type: {{.typ}}
	  name: "{{.name}}"
	  targets {
	    host_names: "www.google.com"
	  }
	}
	{{end}}

	{{template "probeTmpl" mkMap "typ" "PING" "name" "ping_google"}}
	{{template "probeTmpl" mkMap "typ" "HTTP" "name" "http_google"}}

mkSlice
	Returns a slice consisting of the arguments. It can be used with the built-in
	'range' function to replicate text.

	{{with $regions := mkSlice "us=central1" "us-east1"}}
	{{range $_, $region := $regions}}

	probe {
	  name: "service-a-{{$region}}"
	  type: HTTP
	  targets {
	    host_names: "service-a.{{$region}}.corp.xx.com"
	  }
	}

	{{end}}
	{{end}}