Merge ~cgrabowski/maas:spike_prometheus_exporter into ~cgrabowski/maas:rack_region_redesign_spike

[Christian Grabowski]

add root metrics registry

add prometheus export

[Alexsander de Souza (alexsander-souza)]

Just minor remarks

review: Approve

[Christian Grabowski (cgrabowski)]

review: Approve

diff --git a/src/rackd_spike/cmd/rackd.go b/src/rackd_spike/cmd/rackd.go
index 7e4d1e5..78d6ef3 100644
--- a/src/rackd_spike/cmd/rackd.go
+++ b/src/rackd_spike/cmd/rackd.go
@@ -12,6 +12,7 @@ import (
 
 	"rackd/cmd/logger"
 	"rackd/cmd/subcommands"
+	"rackd/internal/metrics"
 )
 
 type opts struct {
@@ -53,6 +54,12 @@ var (
 			if err != nil {
 				return err
 			}
+			rootMetricsRegistry := metrics.NewRegistry("")
+			metricsSrvr, err := metrics.NewPrometheus("127.0.0.1", 9090, nil, rootMetricsRegistry) // TODO make bind address configurable and provide TLS config
+			if err != nil {
+				return err
+			}
+			defer metricsSrvr.Close()
 			log.Info().Msg("rackd started successfully")
 			sigChan := make(chan os.Signal)
 			signal.Notify(sigChan, syscall.SIGTERM, syscall.SIGINT)
diff --git a/src/rackd_spike/go.mod b/src/rackd_spike/go.mod
index c50f1cc..2a2e641 100644
--- a/src/rackd_spike/go.mod
+++ b/src/rackd_spike/go.mod
@@ -3,6 +3,7 @@ module rackd
 go 1.13
 
 require (
+	github.com/prometheus/client_golang v0.9.3
 	github.com/rs/zerolog v1.23.0
 	github.com/spf13/cobra v1.1.3
 )
diff --git a/src/rackd_spike/go.sum b/src/rackd_spike/go.sum
index 4639daf..65479d3 100644
--- a/src/rackd_spike/go.sum
+++ b/src/rackd_spike/go.sum
@@ -20,6 +20,7 @@ github.com/armon/circbuf v0.0.0-20150827004946-bbbad097214e/go.mod h1:3U/XgcO3hC
 github.com/armon/go-metrics v0.0.0-20180917152333-f0300d1749da/go.mod h1:Q73ZrmVTwzkszR9V5SSuryQ31EELlFMUz1kKyl939pY=
 github.com/armon/go-radix v0.0.0-20180808171621-7fddfc383310/go.mod h1:ufUuZ+zHj4x4TnLV4JWEpy2hxWSpsRywHrMgIH9cCH8=
 github.com/beorn7/perks v0.0.0-20180321164747-3a771d992973/go.mod h1:Dwedo/Wpr24TaqPxmxbtue+5NUziq4I4S80YR8gNf3Q=
+github.com/beorn7/perks v1.0.0 h1:HWo1m869IqiPhD389kmkxeTalrjNbbJTC8LXupb+sl0=
 github.com/beorn7/perks v1.0.0/go.mod h1:KWe93zE9D1o94FZ5RNwFwVgaQK1VOXiVxmqh+CedLV8=
 github.com/bgentry/speakeasy v0.1.0/go.mod h1:+zsyZBPWlz7T6j88CTgSN5bM796AkVf0kBD4zp0CCIs=
 github.com/bketelsen/crypt v0.0.3-0.20200106085610-5cbc8cc4026c/go.mod h1:MKsuJmJgSg28kpZDP6UIiPt0e0Oz0kqKNGyRaWEPv84=
@@ -54,6 +55,7 @@ github.com/golang/mock v1.2.0/go.mod h1:oTYuIxOrZwtPieC+H1uAHpcLFnEyAGVDL/k47Jfb
 github.com/golang/mock v1.3.1/go.mod h1:sBzyDLLjw3U8JLTeZvSv8jJB+tU5PVekmnlKIyFUx0Y=
 github.com/golang/protobuf v1.2.0/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=
 github.com/golang/protobuf v1.3.1/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=
+github.com/golang/protobuf v1.3.2 h1:6nsPYzhq5kReh6QImI3k5qWzO4PEbvbIW2cwSfR/6xs=
 github.com/golang/protobuf v1.3.2/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=
 github.com/google/btree v0.0.0-20180813153112-4030bb1f1f0c/go.mod h1:lNA+9X1NB3Zf8V7Ke586lFgjr2dZNuvo3lPJSGZ5JPQ=
 github.com/google/btree v1.0.0/go.mod h1:lNA+9X1NB3Zf8V7Ke586lFgjr2dZNuvo3lPJSGZ5JPQ=
@@ -106,6 +108,7 @@ github.com/kr/text v0.1.0/go.mod h1:4Jbv+DJW3UT/LiOwJeYQe1efqtUx/iVham/4vfdArNI=
 github.com/magiconair/properties v1.8.1/go.mod h1:PppfXfuXeibc/6YijjN8zIbojt8czPbwD3XqdrwzmxQ=
 github.com/mattn/go-colorable v0.0.9/go.mod h1:9vuHe8Xs5qXnSaW/c/ABM9alt+Vo+STaOChaDxuIBZU=
 github.com/mattn/go-isatty v0.0.3/go.mod h1:M+lRXTBqGeGNdLjl/ufCoiOlB5xdOkqRJdNxMWT7Zi4=
+github.com/matttproud/golang_protobuf_extensions v1.0.1 h1:4hp9jkHxhMHkqkrB3Ix0jegS5sx/RkqARlsWZ6pIwiU=
 github.com/matttproud/golang_protobuf_extensions v1.0.1/go.mod h1:D8He9yQNgCq6Z5Ld7szi9bcBfOoFv/3dc6xSMkL2PC0=
 github.com/miekg/dns v1.0.14/go.mod h1:W1PPwlIAgtquWBMBEV9nkV9Cazfe8ScdGz/Lj7v3Nrg=
 github.com/mitchellh/cli v1.0.0/go.mod h1:hNIlj7HEI86fIcpObd7a0FcrxTWetlwJDGcceTlRvqc=
@@ -128,12 +131,16 @@ github.com/pkg/errors v0.9.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINE
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/posener/complete v1.1.1/go.mod h1:em0nMJCgc9GFtwrmVmEMR/ZL6WyhyjMBndrE9hABlRI=
 github.com/prometheus/client_golang v0.9.1/go.mod h1:7SWBe2y4D6OKWSNQJUaRYU/AaXPKyh/dDVn+NZz0KFw=
+github.com/prometheus/client_golang v0.9.3 h1:9iH4JKXLzFbOAdtqv/a+j8aewx2Y8lAjAydhbaScPF8=
 github.com/prometheus/client_golang v0.9.3/go.mod h1:/TN21ttK/J9q6uSwhBd54HahCDft0ttaMvbicHlPoso=
 github.com/prometheus/client_model v0.0.0-20180712105110-5c3871d89910/go.mod h1:MbSGuTsp3dbXC40dX6PRTWyKYBIrTGTE9sqQNg2J8bo=
+github.com/prometheus/client_model v0.0.0-20190129233127-fd36f4220a90 h1:S/YWwWx/RA8rT8tKFRuGUZhuA90OyIBpPCXkcbwU8DE=
 github.com/prometheus/client_model v0.0.0-20190129233127-fd36f4220a90/go.mod h1:xMI15A0UPsDsEKsMN9yxemIoYk6Tm2C1GtYGdfGttqA=
 github.com/prometheus/common v0.0.0-20181113130724-41aa239b4cce/go.mod h1:daVV7qP5qjZbuso7PdcryaAu0sAZbrN9i7WWcTMWvro=
+github.com/prometheus/common v0.4.0 h1:7etb9YClo3a6HjLzfl6rIQaU+FDfi0VSX39io3aQ+DM=
 github.com/prometheus/common v0.4.0/go.mod h1:TNfzLD0ON7rHzMJeJkieUDPYmFC7Snx/y86RQel1bk4=
 github.com/prometheus/procfs v0.0.0-20181005140218-185b4288413d/go.mod h1:c3At6R/oaqEKCNdg8wHV1ftS6bRYblBhIjjI8uT2IGk=
+github.com/prometheus/procfs v0.0.0-20190507164030-5867b95ac084 h1:sofwID9zm4tzrgykg80hfFph1mryUeLRsUfoocVVmRY=
 github.com/prometheus/procfs v0.0.0-20190507164030-5867b95ac084/go.mod h1:TjEm7ze935MbeOT/UhFTIMYKhuLP4wbCsTZCD3I8kEA=
 github.com/prometheus/tsdb v0.7.1/go.mod h1:qhTCs0VvXwvX/y3TZrWD7rabWM+ijKTux40TwIPHuXU=
 github.com/rogpeppe/fastuuid v0.0.0-20150106093220-6724a57986af/go.mod h1:XWv6SoW27p1b0cqNHllgS5HIMJraePCO15w5zCzIWYg=
diff --git a/src/rackd_spike/internal/metrics/prometheus.go b/src/rackd_spike/internal/metrics/prometheus.go
new file mode 100644
index 0000000..fbda27e
--- /dev/null
+++ b/src/rackd_spike/internal/metrics/prometheus.go
@@ -0,0 +1,46 @@
+package metrics
+
+import (
+	"crypto/tls"
+	"net"
+	"net/http"
+	"strconv"
+
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promhttp"
+)
+
+type Registry struct {
+	prometheus.Registry
+	Name string
+}
+
+func NewRegistry(name string) *Registry {
+	return &Registry{
+		Registry: *prometheus.NewRegistry(),
+		Name:     name,
+	}
+}
+
+func NewPrometheus(host string, port int, tlsConf *tls.Config, registries ...*Registry) (*http.Server, error) {
+	mux := http.NewServeMux()
+	for _, registry := range registries {
+		// TODO add HandlerOpts
+		mux.Handle("/metrics/"+registry.Name, promhttp.HandlerFor(registry, promhttp.HandlerOpts{}))
+	}
+	addr := net.JoinHostPort(host, strconv.Itoa(port))
+	srvr := &http.Server{
+		Addr:      addr,
+		Handler:   mux,
+		TLSConfig: tlsConf,
+	}
+	listener, err := net.Listen("tcp", addr)
+	if err != nil {
+		return nil, err
+	}
+	if tlsConf != nil {
+		listener = tls.NewListener(listener, tlsConf)
+	}
+	go srvr.Serve(listener)
+	return srvr, nil
+}