Merge pull request ipfs/kubo#1422 from lgierth/metrics

Expose metrics via Prometheus

This commit was moved from ipfs/kubo@74a331d

gateway/core/corehttp/prometheus.go

@@ -0,0 +1,16 @@
+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
+	}
+}