The system info metrics now use OpenCensus

changelog/unreleased/sysinfo-cleanup.md

@@ -0,0 +1,5 @@
+Enhancement: System information metrics cleanup
+
+The system information metrics are now based on OpenCensus instead of the Prometheus client library. Furthermore, its initialization was moved out of the Prometheus HTTP service to keep things clean.
+
+https://github.com/cs3org/reva/pull/1114

cmd/revad/main.go

@@ -53,7 +53,10 @@ func main() {
 	flag.Parse()
 
 	// initialize the global system information
-	sysinfo.InitSystemInfo(&sysinfo.RevaVersion{Version: version, BuildDate: buildDate, GitCommit: gitCommit, GoVersion: goVersion})
+	if err := sysinfo.InitSystemInfo(&sysinfo.RevaVersion{Version: version, BuildDate: buildDate, GitCommit: gitCommit, GoVersion: goVersion}); err != nil {
+		fmt.Fprintf(os.Stderr, "error initializing system info: %s\n", err.Error())
+		// This is not really a fatal error, so don't panic
+	}
 
 	handleVersionFlag()
 	handleSignalFlag()

go.mod

@@ -36,7 +36,6 @@ require (
 	github.com/pkg/term v0.0.0-20200520122047-c3ffed290a03 // indirect
 	github.com/pkg/xattr v0.4.1
 	github.com/pquerna/cachecontrol v0.0.0-20180517163645-1555304b9b35 // indirect
-	github.com/prometheus/client_golang v1.7.1
 	github.com/rs/cors v1.7.0
 	github.com/rs/zerolog v1.19.0
 	github.com/stretchr/testify v1.6.1

go.sum

@@ -906,6 +906,7 @@ golang.org/x/sys v0.0.0-20200323222414-85ca7c5b95cd h1:xhmwyvizuTgC2qz7ZlMluP20u
 golang.org/x/sys v0.0.0-20200323222414-85ca7c5b95cd/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20200331124033-c3d80250170d h1:nc5K6ox/4lTFbMVSL9WRR81ixkcwXThoiF6yf+R9scA=
 golang.org/x/sys v0.0.0-20200331124033-c3d80250170d/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20200420163511-1957bb5e6d1f h1:gWF768j/LaZugp8dyS4UwsslYCYz9XgFxvlgsn0n9H8=
 golang.org/x/sys v0.0.0-20200420163511-1957bb5e6d1f/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20200615200032-f1bc736245b1 h1:ogLJMz+qpzav7lGMh10LMvAkM/fAoGlaiiHYiFYdm80=
 golang.org/x/sys v0.0.0-20200615200032-f1bc736245b1/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=

internal/http/services/prometheus/prometheus.go

@@ -24,13 +24,10 @@ import (
 	"contrib.go.opencensus.io/exporter/prometheus"
 	"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"
 )
@@ -48,23 +45,15 @@ 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, sysinfo: sysinfo}, nil
+	return &svc{prefix: conf.Prefix, h: pe}, nil
 }
 
 type config struct {
@@ -80,8 +69,6 @@ func (c *config) init() {
 type svc struct {
 	prefix string
 	h      http.Handler
-
-	sysinfo *sysinfo.PrometheusExporter
 }
 
 func (s *svc) Prefix() string {

pkg/sysinfo/prometheus.go → pkg/sysinfo/metrics.go

@@ -19,43 +19,59 @@
 package sysinfo
 
 import (
+	"context"
 	"fmt"
 	"reflect"
 	"strings"
 
-	"github.com/prometheus/client_golang/prometheus"
+	"github.com/pkg/errors"
+	"go.opencensus.io/stats"
+	"go.opencensus.io/stats/view"
+	"go.opencensus.io/tag"
 
 	"github.com/cs3org/reva/pkg/utils"
 )
 
-// PrometheusExporter exports system information via Prometheus.
-type PrometheusExporter struct {
-	registry      *prometheus.Registry
-	sysInfoMetric prometheus.GaugeFunc
-}
+type sysInfoMetricsLabels = map[tag.Key]string
+
+func registerSystemInfoMetrics() error {
+	labels := getSystemInfoMetricsLabels("", SysInfo)
+
+	// Collect all labels and their values; the values are stored as mutators
+	tagKeys := make([]tag.Key, 0, len(labels))
+	mutators := make([]tag.Mutator, 0, len(labels))
+	for key, value := range labels {
+		tagKeys = append(tagKeys, key)
+		mutators = append(mutators, tag.Insert(key, value))
+	}
+
+	// Create the OpenCensus statistics and a corresponding view
+	sysInfoStats := stats.Int64("sys_info", "A metric with a constant '1' value labeled by various system information elements", stats.UnitDimensionless)
+	sysInfoView := &view.View{
+		Name:        sysInfoStats.Name(),
+		Description: sysInfoStats.Description(),
+		Measure:     sysInfoStats,
+		TagKeys:     tagKeys,
+		Aggregation: view.LastValue(),
+	}
+
+	if err := view.Register(sysInfoView); err != nil {
+		return errors.Wrap(err, "unable to register the system info metrics view")
+	}
 
-func (psysinfo *PrometheusExporter) init(registry *prometheus.Registry) error {
-	// Create all necessary Prometheus objects
-	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),
-		},
-		func() float64 { return 1 },
-	)
-
-	if err := psysinfo.registry.Register(psysinfo.sysInfoMetric); err != nil {
-		return fmt.Errorf("unable to register the system information metrics: %v", err)
+	// Create a new context to serve the metrics
+	if ctx, err := tag.New(context.Background(), mutators...); err == nil {
+		// Just record a simple hardcoded '1' to expose the system info as a metric
+		stats.Record(ctx, sysInfoStats.M(1))
+	} else {
+		return errors.Wrap(err, "unable to create a context for the system info metrics")
 	}
 
 	return nil
 }
 
-func (psysinfo *PrometheusExporter) getLabels(root string, i interface{}) prometheus.Labels {
-	labels := prometheus.Labels{}
+func getSystemInfoMetricsLabels(root string, i interface{}) sysInfoMetricsLabels {
+	labels := sysInfoMetricsLabels{}
 
 	// Iterate over each field of the given interface, recursively collecting the values as labels
 	v := reflect.ValueOf(i).Elem()
@@ -77,27 +93,14 @@ func (psysinfo *PrometheusExporter) getLabels(root string, i interface{}) promet
 		f := v.Field(i)
 		if f.Kind() == reflect.Struct || (f.Kind() == reflect.Ptr && f.Elem().Kind() == reflect.Struct) {
 			// Merge labels recursively
-			for key, val := range psysinfo.getLabels(fieldName, f.Interface()) {
+			for key, val := range getSystemInfoMetricsLabels(fieldName, f.Interface()) {
 				labels[key] = val
 			}
 		} else { // Store the value of the field in the labels
-			labels[fieldName] = fmt.Sprintf("%v", f)
+			key := tag.MustNewKey(fieldName)
+			labels[key] = fmt.Sprintf("%v", f)
 		}
 	}
 
 	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
-}

pkg/sysinfo/reva.go

@@ -21,7 +21,7 @@ package sysinfo
 // RevaVersion stores version information about Reva.
 type RevaVersion struct {
 	Version   string `json:"version"`
-	BuildDate string `json:"build_date" sysinfo:"omitlabel"`
+	BuildDate string `json:"build_date"`
 	GitCommit string `json:"git_commit" sysinfo:"omitlabel"`
 	GoVersion string `json:"go_version" sysinfo:"omitlabel"`
 }

pkg/sysinfo/sysinfo.go

@@ -22,6 +22,8 @@ import (
 	"encoding/json"
 	"fmt"
 	"reflect"
+
+	"github.com/pkg/errors"
 )
 
 // SystemInformation stores general information about Reva and the system it's running on.
@@ -44,16 +46,6 @@ func (sysInfo *SystemInformation) ToJSON() (string, error) {
 	return string(data), nil
 }
 
-// InitSystemInfo initializes the global system information object.
-func InitSystemInfo(revaVersion *RevaVersion) {
-	SysInfo = &SystemInformation{
-		Reva: revaVersion,
-	}
-
-	// Replace any empty values in the system information by more meaningful ones
-	replaceEmptyInfoValues(SysInfo)
-}
-
 func replaceEmptyInfoValues(i interface{}) {
 	// Iterate over each field of the given interface and search for "empty" values
 	v := reflect.ValueOf(i).Elem()
@@ -71,3 +63,20 @@ func replaceEmptyInfoValues(i interface{}) {
 		}
 	}
 }
+
+// InitSystemInfo initializes the global system information object and also registers the corresponding metrics.
+func InitSystemInfo(revaVersion *RevaVersion) error {
+	SysInfo = &SystemInformation{
+		Reva: revaVersion,
+	}
+
+	// Replace any empty values in the system information by more meaningful ones
+	replaceEmptyInfoValues(SysInfo)
+
+	// Register the system information metrics, as the necessary system info object has been filled out
+	if err := registerSystemInfoMetrics(); err != nil {
+		return errors.Wrap(err, "unable to register the system info metrics")
+	}
+
+	return nil
+}