From 0897e9970167c22cf4f3ccd54bcb2869ce0f40ac Mon Sep 17 00:00:00 2001
From: pancho horrillo <pedrofelipe.horrillo@bbva.com>
Date: Fri, 1 Feb 2019 11:44:35 +0100
Subject: [PATCH] Use prometheus.Gatherers to avoid duplicating std collectors

Seen on github.com/minio/minio/cmd/metrics.go

This way, the ProcessCollector and the GoCollector will operate on the
Prometheus DefaultRegistry, whose durability is the same as the process.

On the other hand, the registry we instantiate per server will live and die with
it.

I was inclined to implement this because I think that otherwise we ended up with
a redundant set of *Collectors, ones instantiated by us, and the othe ones
instantiated by the prometheus library, as goodies of the DefaultRegistry.

Besides, now I know how to make use of multiple registries (via Gatherers, which
kinda melds them).
---
 api/metricshttp/metricshttp.go | 6 +++++-
 server/server.go               | 9 ---------
 2 files changed, 5 insertions(+), 10 deletions(-)

diff --git a/api/metricshttp/metricshttp.go b/api/metricshttp/metricshttp.go
index b30015bf8..ae381fbd4 100644
--- a/api/metricshttp/metricshttp.go
+++ b/api/metricshttp/metricshttp.go
@@ -9,12 +9,16 @@ import (
 
 func NewMetricsHTTP(r *prometheus.Registry) *http.ServeMux {
 	mux := http.NewServeMux()
+	g := prometheus.Gatherers{
+		prometheus.DefaultGatherer,
+		r,
+	}
 	mux.Handle(
 		"/metrics",
 		promhttp.InstrumentMetricHandler(
 			r,
 			promhttp.HandlerFor(
-				r,
+				g,
 				promhttp.HandlerOpts{},
 			),
 		),
diff --git a/server/server.go b/server/server.go
index 21b7676e9..f5657b218 100644
--- a/server/server.go
+++ b/server/server.go
@@ -175,15 +175,6 @@ func NewServer(conf *Config) (*Server, error) {
 		server.prometheusRegistry = r
 		metricsMux := metricshttp.NewMetricsHTTP(r)
 
-		r.MustRegister(
-			prometheus.NewProcessCollector(
-				prometheus.ProcessCollectorOpts{},
-			),
-		)
-		r.MustRegister(
-			prometheus.NewGoCollector(),
-		)
-
 		server.metricsServer = newHTTPServer("localhost:9990", metricsMux)
 	}