Enable metrics on /metrics, add '--environment' flag, add 'xxx_info' gauge

go.mod

@@ -10,7 +10,7 @@
 	github.com/go-openapi/swag v0.19.9
 	github.com/golang-migrate/migrate/v4 v4.12.2
 	github.com/jmoiron/sqlx v1.2.1-0.20200615141059-0794cb1f47ee
-	github.com/json-iterator/go v1.1.6
+	github.com/json-iterator/go v1.1.10
 	github.com/justinas/alice v1.2.0
 	github.com/lann/builder v0.0.0-20180802200727-47ae307949d0
 	github.com/orus-io/go-flags v1.4.0
@@ -14,6 +14,7 @@
 	github.com/justinas/alice v1.2.0
 	github.com/lann/builder v0.0.0-20180802200727-47ae307949d0
 	github.com/orus-io/go-flags v1.4.0
+	github.com/prometheus/client_golang v1.8.0
 	github.com/rs/zerolog v1.19.0
 	github.com/stretchr/testify v1.6.1
 	golang.org/x/crypto v0.0.0-20200820211705-5c72a883971a

prometheus_middleware.go

+package orusapi
+
+import (
+	"fmt"
+	"net/http"
+	"strings"
+
+	"github.com/prometheus/client_golang/prometheus/promhttp"
+)
+
+// Prometheus serves the '/metrics' endpoint
+func Prometheus(path string) func(next http.Handler) http.Handler {
+	handler := promhttp.Handler()
+
+	return func(next http.Handler) http.Handler {
+		return http.HandlerFunc(func(rw http.ResponseWriter, r *http.Request) {
+			if strings.HasPrefix(r.URL.Path, path) {
+				handler.ServeHTTP(rw, r)
+				return
+			}
+
+			if next == nil {
+				rw.Header().Set("Content-Type", "text/plain")
+				rw.WriteHeader(http.StatusNotFound)
+				_, _ = rw.Write([]byte(fmt.Sprintf("%q not found", path)))
+				return
+			}
+			next.ServeHTTP(rw, r)
+		})
+	}
+}

server.go

@@ -90,6 +90,8 @@
 
 	Prometheus bool `long:"prometheus" description:"enable prometheus metrics on /metrics"`
 
+	Environment string `no-flag:"t" description:"A environment name"`
+
 	api          API
 	log          zerolog.Logger
 	handler      http.Handler
@@ -449,6 +451,9 @@
 // SetHandler allows for setting a http handler on this server
 func (s *Server) SetHandler(handler http.Handler) {
 	s.handler = handler
+	if s.Prometheus {
+		s.handler = Prometheus("/metrics")(s.handler)
+	}
 }
 
 // UnixListener returns the domain socket listener

templates/server/cmd.gotmpl

@@ -8,7 +8,11 @@
 	"orus.io/orus-io/go-orusapi/database"
 )
 
+var (
+    Version string
+)
+
 type ConfigFile struct {
 	ConfigFile string `long:"config" short:"c" env:"CONFIG" no-ini:"t" description:"A configuration file"`
 }
 
@@ -11,9 +15,13 @@
 type ConfigFile struct {
 	ConfigFile string `long:"config" short:"c" env:"CONFIG" no-ini:"t" description:"A configuration file"`
 }
 
+type Info struct {
+    Environment string `long:"environment" env:"ENVIRONMENT" ini-name:"environment" default:"default" description:"A environment name, used in sentry and prometheus"`
+}
+
 var (
 	Logger = orusapi.DefaultLogger(os.Stdout)
 	LoggingOptions  = orusapi.MustLoggingOptions(orusapi.NewLoggingOptions(&Logger, os.Stdout))
 	DatabaseOptions = &database.Options{}
 	ConfigFileOption = &ConfigFile{}
@@ -15,8 +23,10 @@
 var (
 	Logger = orusapi.DefaultLogger(os.Stdout)
 	LoggingOptions  = orusapi.MustLoggingOptions(orusapi.NewLoggingOptions(&Logger, os.Stdout))
 	DatabaseOptions = &database.Options{}
 	ConfigFileOption = &ConfigFile{}
+    InfoOptions = &Info{}
+
 	SentryOptions = orusapi.NewSentryOptions(LoggingOptions)
 
 	parser = flags.NewNamedParser("{{ dasherize (pascalize .Name) }}", flags.HelpFlag|flags.PassDoubleDash)
@@ -64,7 +74,12 @@
 	if _, err := parser.AddGroup("Configuration", "Configuration file", ConfigFileOption); err != nil {
 		panic(err)
 	}
-	g, err := parser.AddGroup("Logging", "Logging options", LoggingOptions)
+    g, err := parser.AddGroup("Info", "Info options", InfoOptions)
+    if err != nil {
+        panic(err)
+    }
+
+	g, err = parser.AddGroup("Logging", "Logging options", LoggingOptions)
 	if err != nil {
 		panic(err)
 	}

templates/server/cmdServe.gotmpl

@@ -65,7 +65,21 @@
 	}
 
 	if cmd.Server.Prometheus {
+		var infoGauge = prometheus.NewGauge(prometheus.GaugeOpts{
+			Name: "{{ snakize .Name }}_info",
+			Help: "Informations about the {{ pascalize .Name }} server",
+			ConstLabels: map[string]string{
+				"environment":  InfoOptions.Environment,
+				"version":  Version,
+			},
+		})
+		infoGauge.Set(1)
+		if err := prometheus.Register(infoGauge); err != nil {
+			return err
+		}
+		defer prometheus.Unregister(infoGauge)
+
 		collector := sqlstats.NewStatsCollector("db", db)
 		if err := prometheus.Register(collector); err != nil {
 			return err
 		}
@@ -68,7 +82,8 @@
 		collector := sqlstats.NewStatsCollector("db", db)
 		if err := prometheus.Register(collector); err != nil {
 			return err
 		}
+		defer prometheus.Unregister(collector)
 	}
 
 	config := restapi.Config{
@@ -80,6 +95,7 @@
 	}
 
 	cmd.Server.SetLog(Logger)
+    cmd.Server.Environment = InfoOptions.Environment
 
 	configuredAPI, err := restapi.ConfigureAPI(cmd.API, config)
 	if err != nil {