Prometheus endpoint (#5256)

* Add prometheus collector and route

* dep ensure -add github.com/prometheus/client_golang/prometheus

* dep ensure -update github.com/golang/protobuf

* add metrics to reserved usernames

* add comment head in metrics package

* fix style imports

* add metrics settings

* add bearer token check

* mapping metrics configs

* fix lint

* update config cheat sheet

* update conf sample, typo fix

2 files changed, 40 insertions, 0 deletions

diff --git a/routers/metrics.go b/routers/metrics.go
new file mode 100644
index 0000000000..e70918f068
--- /dev/null
+++ b/routers/metrics.go
@@ -0,0 +1,30 @@
+// Copyright 2018 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package routers
+
+import (
+	"github.com/prometheus/client_golang/prometheus/promhttp"
+
+	"code.gitea.io/gitea/modules/context"
+	"code.gitea.io/gitea/modules/setting"
+)
+
+// Metrics validate auth token and render prometheus metrics
+func Metrics(ctx *context.Context) {
+	if setting.Metrics.Token == "" {
+		promhttp.Handler().ServeHTTP(ctx.Resp, ctx.Req.Request)
+		return
+	}
+	header := ctx.Header().Get("Authorization")
+	if header == "" {
+		ctx.Error(401)
+		return
+	}
+	if header != "Bearer "+setting.Metrics.Token {
+		ctx.Error(401)
+		return
+	}
+	promhttp.Handler().ServeHTTP(ctx.Resp, ctx.Req.Request)
+}
diff --git a/routers/routes/routes.go b/routers/routes/routes.go
index 5e54934a36..af216866bb 100644
--- a/routers/routes/routes.go
+++ b/routers/routes/routes.go
@@ -16,6 +16,7 @@ import (
 	"code.gitea.io/gitea/modules/context"
 	"code.gitea.io/gitea/modules/lfs"
 	"code.gitea.io/gitea/modules/log"
+	"code.gitea.io/gitea/modules/metrics"
 	"code.gitea.io/gitea/modules/options"
 	"code.gitea.io/gitea/modules/public"
 	"code.gitea.io/gitea/modules/setting"
@@ -39,6 +40,7 @@ import (
 	"github.com/go-macaron/i18n"
 	"github.com/go-macaron/session"
 	"github.com/go-macaron/toolbox"
+	"github.com/prometheus/client_golang/prometheus"
 	"github.com/tstranex/u2f"
 	"gopkg.in/macaron.v1"
 )
@@ -788,6 +790,14 @@ func RegisterRoutes(m *macaron.Macaron) {
 		}
 	})
 
+	// prometheus metrics endpoint
+	if setting.Metrics.Enabled {
+		c := metrics.NewCollector()
+		prometheus.MustRegister(c)
+
+		m.Get("/metrics", routers.Metrics)
+	}
+
 	// Not found handler.
 	m.NotFound(routers.NotFound)
 }