Function ExampleCollectorFunc

prometheus/examples_test.go:743–788

Using CollectorFunc that registers the metric info for the HTTP requests.

()

// Using CollectorFunc that registers the metric info for the HTTP requests.
func ExampleCollectorFunc() {
	desc := prometheus.NewDesc(
		"http_requests_info",
		"Information about the received HTTP requests.",
		[]string{"code", "method"},
		nil,
	)

	// Example 1: 42 GET requests with 200 OK status code.
	collector := prometheus.CollectorFunc(func(ch chan<- prometheus.Metric) {
		ch <- prometheus.MustNewConstMetric(
			desc,
			prometheus.CounterValue, // Metric type: Counter
			42,                      // Value
			"200",                   // Label value: HTTP status code
			"GET",                   // Label value: HTTP method
		)

		// Example 2: 15 POST requests with 404 Not Found status code.
		ch <- prometheus.MustNewConstMetric(
			desc,
			prometheus.CounterValue,
			15,
			"404",
			"POST",
		)
	})

	prometheus.MustRegister(collector)

	// Just for demonstration, let's check the state of the metric by registering
	// it with a custom registry and then let it collect the metrics.

	reg := prometheus.NewRegistry()
	reg.MustRegister(collector)

	metricFamilies, err := reg.Gather()
	if err != nil || len(metricFamilies) != 1 {
		panic("unexpected behavior of custom test registry")
	}

	fmt.Println(toNormalizedJSON(sanitizeMetricFamily(metricFamilies[0])))

	// Output:
	// {"name":"http_requests_info","help":"Information about the received HTTP requests.","type":"COUNTER","metric":[{"label":[{"name":"code","value":"200"},{"name":"method","value":"GET"}],"counter":{"value":42}},{"label":[{"name":"code","value":"404"},{"name":"method","value":"POST"}],"counter":{"value":15}}]}
}

// Using WrapCollectorWith to un-register metrics registered by a third party lib.
// newThirdPartyLibFoo illustrates a constructor from a third-party lib that does