api: add /metrics endpoint for prometheus

License: MIT
Signed-off-by: Lars Gierth <larsg@systemli.org>

cmd/ipfs/daemon.go

@@ -300,6 +300,7 @@ func serveHTTPApi(req cmds.Request) (error, <-chan error) {
 		defaultMux("/debug/vars"),
 		defaultMux("/debug/pprof/"),
 		corehttp.LogOption(),
+		corehttp.PrometheusOption("/debug/metrics/prometheus"),
 	}
 
 	if len(cfg.Gateway.RootRedirect) > 0 {

core/corehttp/prometheus.go

+package corehttp
+
+import (
+	"net/http"
+
+	prom "github.com/ipfs/go-ipfs/Godeps/_workspace/src/github.com/prometheus/client_golang/prometheus"
+
+	"github.com/ipfs/go-ipfs/core"
+)
+
+func PrometheusOption(path string) ServeOption {
+	return func(n *core.IpfsNode, mux *http.ServeMux) (*http.ServeMux, error) {
+		mux.Handle(path, prom.Handler())
+		return mux, nil
+	}
+}