Instrumenting a Go application for Prometheus

    NOTE: For comprehensive API documentation, see the GoDoc for Prometheus' various Go libraries.

    You can install the , promauto, and promhttp libraries necessary for the guide using :

    To expose Prometheus metrics in a Go application, you need to provide a /metrics HTTP endpoint. You can use the prometheus/promhttp library's HTTP as the handler function.

    1. package main
    3. import (
    4.         "net/http"
    6.         "github.com/prometheus/client_golang/prometheus/promhttp"
    7. )
    9. func main() {
    10.         http.Handle("/metrics", promhttp.Handler())
    11.         http.ListenAndServe(":2112", nil)
    12. }

    To start the application:

    1. go run main.go

    To access the metrics:

    The application above exposes only the default Go metrics. You can also register your own custom application-specific metrics. This example application exposes a myapp_processed_ops_total that counts the number of operations that have been processed thus far. Every 2 seconds, the counter is incremented by one.

    2. import (
    3.         "net/http"
    4.         "time"
    6.         "github.com/prometheus/client_golang/prometheus"
    7.         "github.com/prometheus/client_golang/prometheus/promauto"
    8.         "github.com/prometheus/client_golang/prometheus/promhttp"
    9. )
    11. func recordMetrics() {
    12.         go func() {
    13.                 for {
    14.                         opsProcessed.Inc()
    15.                         time.Sleep(2 * time.Second)
    16.                 }
    17.         }()
    18. }
    20. var (
    22.                 Help: "The total number of processed events",
    23.         })
    24. )
    26. func main() {
    27.         recordMetrics()
    29.         http.Handle("/metrics", promhttp.Handler())
    30.         http.ListenAndServe(":2112", nil)
    31. }
    1. go run main.go

    To access the metrics:

    In the metrics output, you'll see the help text, type information, and current value of the myapp_processed_ops_total counter:

    1. # HELP myapp_processed_ops_total The total number of processed events
    2. # TYPE myapp_processed_ops_total counter
    3. myapp_processed_ops_total 5

    You can configure a locally running Prometheus instance to scrape metrics from the application. Here's an example prometheus.yml configuration:

    1. scrape_configs:
    2. - job_name: myapp
    3.   scrape_interval: 10s
    4.   static_configs:

    In this guide, you created two sample Go applications that expose metrics to Prometheus—-one that exposes only the default Go metrics and one that also exposes a custom Prometheus counter—-and configured a Prometheus instance to scrape metrics from those applications.