feat: expose unprotected metrics endpoint (#1614)

Signed-off-by: Alexander Matyushentsev <AMatyushentsev@gmail.com>
Co-authored-by: Lauris BH <lauris@nix.lv>
Co-authored-by: Anbraten <anton@ju60.de>

cmd/server/flags.go

@@ -77,6 +77,12 @@ var flags = []cli.Flag{
 		Usage:   "grpc address",
 		Value:   ":9000",
 	},
+	&cli.StringFlag{
+		EnvVars: []string{"WOODPECKER_METRICS_SERVER_ADDR"},
+		Name:    "metrics-server-addr",
+		Usage:   "metrics server address",
+		Value:   "",
+	},
 	&cli.StringSliceFlag{
 		EnvVars: []string{"WOODPECKER_ADMIN"},
 		Name:    "admin",

cmd/server/server.go

@@ -27,6 +27,7 @@ import (
 
 	"github.com/caddyserver/certmagic"
 	"github.com/gin-gonic/gin"
+	"github.com/prometheus/client_golang/prometheus/promhttp"
 	"github.com/rs/zerolog"
 	"github.com/rs/zerolog/log"
 	"github.com/urfave/cli/v2"
@@ -258,6 +259,14 @@ func run(c *cli.Context) error {
 		})
 	}
 
+	if metricsServerAddr := c.String("metrics-server-addr"); metricsServerAddr != "" {
+		g.Go(func() error {
+			metricsRouter := gin.New()
+			metricsRouter.GET("/metrics", gin.WrapH(promhttp.Handler()))
+			return http.ListenAndServe(metricsServerAddr, metricsRouter)
+		})
+	}
+
 	log.Info().Msgf("Starting Woodpecker server with version '%s'", version.String())
 
 	return g.Wait()

docs/docs/30-administration/10-server-config.md

@@ -160,6 +160,12 @@ Automatically generates an SSL certificate using Let's Encrypt, and configures t
 
 Configures the gRPC listener port.
 
+### `WOODPECKER_METRICS_SERVER_ADDR`
+> Default: empty
+
+Configures an unprotected metrics endpoint. An empty value disables the metrics endpoint completely.
+
+Example: `:9001`
 
 ### `WOODPECKER_ADMIN`
 > Default: empty

docs/docs/30-administration/90-prometheus.md

@@ -30,6 +30,10 @@ scrape_configs:
        - targets: ['woodpecker.domain.com']
 ```
 
+## Unauthenticated Access
+
+Alternatively, the unprotected `/metrics` endpoint might be exposed on the internal port. (Port is configurable via the `WOODPECKER_METRICS_SERVER_ADDR` environment variable, e.g. `:9001`.)
+
 ## Metric Reference
 
 List of Prometheus metrics specific to Woodpecker: