From 3a255230ec56911ce9404f240ece4acd0f1cd6eb Mon Sep 17 00:00:00 2001
From: Jason Riddle <jallriddle@gmail.com>
Date: Thu, 27 Apr 2017 16:49:28 -0400
Subject: [PATCH] Add /api/metrics/prometheus endpoint

---
 router/router.go             |  9 +++++++++
 server/metrics/prometheus.go | 14 ++++++++++++++
 2 files changed, 23 insertions(+)
 create mode 100644 server/metrics/prometheus.go

diff --git a/router/router.go b/router/router.go
index aa25fa71..0041b74a 100644
--- a/router/router.go
+++ b/router/router.go
@@ -11,6 +11,7 @@ import (
 	"github.com/drone/drone/router/middleware/token"
 	"github.com/drone/drone/server"
 	"github.com/drone/drone/server/debug"
+	"github.com/drone/drone/server/metrics"
 	"github.com/drone/drone/server/template"
 
 	"github.com/drone/drone-ui/dist"
@@ -171,6 +172,14 @@ func Load(middleware ...gin.HandlerFunc) http.Handler {
 		debugger.GET("/pprof/trace", debug.TraceHandler())
 	}
 
+	monitor := e.Group("/api/metrics")
+	{
+		monitor.GET("/prometheus",
+			session.MustAdmin(),
+			metrics.PromHandler(),
+		)
+	}
+
 	return e
 }
 
diff --git a/server/metrics/prometheus.go b/server/metrics/prometheus.go
new file mode 100644
index 00000000..1eea8961
--- /dev/null
+++ b/server/metrics/prometheus.go
@@ -0,0 +1,14 @@
+package metrics
+
+import (
+	"github.com/gin-gonic/gin"
+
+	"github.com/prometheus/client_golang/prometheus/promhttp"
+)
+
+// PromHandler will pass the call from /api/metrics/prometheus to prometheus
+func PromHandler() gin.HandlerFunc {
+	return func(c *gin.Context) {
+		promhttp.Handler().ServeHTTP(c.Writer, c.Request)
+	}
+}