Merged the SysInfo Prometheus exporter into the existing Prometheus s…

…ervice (cs3org#1071)

changelog/unreleased/sysinfo-prometheus.md

@@ -0,0 +1,5 @@
+Enhancement: System information included in Prometheus metrics
+
+System information is now included in the main Prometheus metrics exposed at `/metrics`. 
+
+https://github.com/cs3org/reva/pull/1071

internal/http/services/prometheus/prometheus.go

@@ -22,12 +22,15 @@ import (
 	"net/http"
 
 	"contrib.go.opencensus.io/exporter/prometheus"
-	"github.com/cs3org/reva/pkg/rhttp/global"
 	"github.com/mitchellh/mapstructure"
 	"github.com/pkg/errors"
+	promclient "github.com/prometheus/client_golang/prometheus"
 	"github.com/rs/zerolog"
 	"go.opencensus.io/stats/view"
 
+	"github.com/cs3org/reva/pkg/rhttp/global"
+	"github.com/cs3org/reva/pkg/sysinfo"
+
 	// Initializes goroutines which periodically update stats
 	_ "github.com/cs3org/reva/pkg/metrics/reader/dummy"
 )
@@ -45,15 +48,23 @@ func New(m map[string]interface{}, log *zerolog.Logger) (global.Service, error)
 
 	conf.init()
 
+	registry := promclient.NewRegistry() // A Prometheus registry shared by OpenCensus and SysInfo
 	pe, err := prometheus.NewExporter(prometheus.Options{
 		Namespace: "revad",
+		Registry:  registry,
 	})
 	if err != nil {
 		return nil, errors.Wrap(err, "prometheus: error creating exporter")
 	}
 
+	// Initialize the SysInfo Prometheus exporter
+	sysinfo, err := sysinfo.NewPrometheusExporter(registry)
+	if err != nil {
+		return nil, errors.Wrap(err, "prometheus: unable to create system info exporter")
+	}
+
 	view.RegisterExporter(pe)
-	return &svc{prefix: conf.Prefix, h: pe}, nil
+	return &svc{prefix: conf.Prefix, h: pe, sysinfo: sysinfo}, nil
 }
 
 type config struct {
@@ -69,6 +80,8 @@ func (c *config) init() {
 type svc struct {
 	prefix string
 	h      http.Handler
+
+	sysinfo *sysinfo.PrometheusExporter
 }
 
 func (s *svc) Prefix() string {

internal/http/services/sysinfo/sysinfo.go

@@ -20,7 +20,6 @@ package sysinfo
 
 import (
 	"net/http"
-	"strings"
 
 	"github.com/mitchellh/mapstructure"
 	"github.com/pkg/errors"
@@ -41,8 +40,6 @@ type config struct {
 
 type svc struct {
 	conf *config
-
-	promHandler *prometheusSysInfoHandler
 }
 
 const (
@@ -67,24 +64,9 @@ func (s *svc) Unprotected() []string {
 // Handler serves all HTTP requests.
 func (s *svc) Handler() http.Handler {
 	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		fmt := strings.ToLower(r.URL.Query().Get("format"))
-		if len(fmt) == 0 {
-			// No format was specified, so let Prometheus handle the request
-			s.promHandler.httpHandler.ServeHTTP(w, r)
-		} else {
-			// Otherwise, provide the system information in the requested format
-			data := ""
-			switch fmt {
-			case "json":
-				data = s.getJSONData()
-			default:
-				data = "Unsupported format"
-			}
-
-			log := appctx.GetLogger(r.Context())
-			if _, err := w.Write([]byte(data)); err != nil {
-				log.Err(err).Msg("error writing SysInfo response")
-			}
+		log := appctx.GetLogger(r.Context())
+		if _, err := w.Write([]byte(s.getJSONData())); err != nil {
+			log.Err(err).Msg("error writing SysInfo response")
 		}
 	})
 }
@@ -120,16 +102,9 @@ func New(m map[string]interface{}, log *zerolog.Logger) (global.Service, error)
 		return nil, err
 	}
 
-	// Create the Prometheus system information handler
-	promHandler := &prometheusSysInfoHandler{}
-	if err := promHandler.init(); err != nil {
-		return nil, err
-	}
-
 	// Create the service
 	s := &svc{
-		conf:        conf,
-		promHandler: promHandler,
+		conf: conf,
 	}
 	return s, nil
 }

internal/http/services/sysinfo/prometheus.go → pkg/sysinfo/prometheus.go

@@ -20,46 +20,41 @@ package sysinfo
 
 import (
 	"fmt"
-	"net/http"
 	"reflect"
 	"strings"
 
 	"github.com/prometheus/client_golang/prometheus"
-	"github.com/prometheus/client_golang/prometheus/promhttp"
 
-	"github.com/cs3org/reva/pkg/sysinfo"
 	"github.com/cs3org/reva/pkg/utils"
 )
 
-type prometheusSysInfoHandler struct {
+// PrometheusExporter exports system information via Prometheus.
+type PrometheusExporter struct {
 	registry      *prometheus.Registry
 	sysInfoMetric prometheus.GaugeFunc
-
-	httpHandler http.Handler
 }
 
-func (psysinfo *prometheusSysInfoHandler) init() error {
+func (psysinfo *PrometheusExporter) init(registry *prometheus.Registry) error {
 	// Create all necessary Prometheus objects
-	psysinfo.registry = prometheus.NewRegistry()
+	psysinfo.registry = registry
 	psysinfo.sysInfoMetric = prometheus.NewGaugeFunc(
 		prometheus.GaugeOpts{
 			Namespace:   "revad",
 			Name:        "sys_info",
 			Help:        "A metric with a constant '1' value labeled by various system information elements",
-			ConstLabels: psysinfo.getLabels("", sysinfo.SysInfo),
+			ConstLabels: psysinfo.getLabels("", SysInfo),
 		},
 		func() float64 { return 1 },
 	)
-	psysinfo.httpHandler = promhttp.HandlerFor(psysinfo.registry, promhttp.HandlerOpts{})
 
 	if err := psysinfo.registry.Register(psysinfo.sysInfoMetric); err != nil {
-		return fmt.Errorf("unable to register the system information metric: %v", err)
+		return fmt.Errorf("unable to register the system information metrics: %v", err)
 	}
 
 	return nil
 }
 
-func (psysinfo *prometheusSysInfoHandler) getLabels(root string, i interface{}) prometheus.Labels {
+func (psysinfo *PrometheusExporter) getLabels(root string, i interface{}) prometheus.Labels {
 	labels := prometheus.Labels{}
 
 	// Iterate over each field of the given interface, recursively collecting the values as labels
@@ -92,3 +87,17 @@ func (psysinfo *prometheusSysInfoHandler) getLabels(root string, i interface{})
 
 	return labels
 }
+
+// NewPrometheusExporter creates a new Prometheus system information exporter.
+func NewPrometheusExporter(registry *prometheus.Registry) (*PrometheusExporter, error) {
+	if registry == nil {
+		return nil, fmt.Errorf("no registry provided")
+	}
+
+	exporter := &PrometheusExporter{}
+	if err := exporter.init(registry); err != nil {
+		return nil, err
+	}
+
+	return exporter, nil
+}