feature: add prometheus metrics (#990)

.github/workflows/build.yml

@@ -187,10 +187,12 @@ jobs:
           docker run \
             --pull never \
             -p 3000:3000 \
+            -p 4000:4000 \
             --env DATABASE_URL=postgres://fider_ci:fider_ci_pw@postgres:5432/fider_ci?sslmode=disable \
             --env JWT_SECRET=not_so_secret \
             --env HOST_MODE=multi \
             --env HOST_DOMAIN=dev.fider.io \
+            --env METRICS_ENABLED=true \
             --env SSL_CERT=dev-fider-io.crt \
             --env SSL_CERT_KEY=dev-fider-io.key \
             --env EMAIL_NOREPLY=noreply@fider.io \

.test.env

@@ -5,6 +5,8 @@ DATABASE_URL=postgres://fider_test:fider_test_pw@localhost:5566/fider_test?sslmo
 HOST_DOMAIN=test.fider.io
 JWT_SECRET=SOME_RANDOM_TOKEN_JUST_FOR_TESTING
 
+METRICS_ENABLED=true
+
 BLOB_STORAGE=s3
 BLOB_STORAGE_S3_ENDPOINT_URL=http://localhost:9000
 BLOB_STORAGE_S3_REGION=us-east-1
@@ -14,8 +16,6 @@ BLOB_STORAGE_S3_BUCKET=test-bucket
 
 BLOB_STORAGE_FS_PATH=./testdata/tmp/fs_test
 
-CDN_HOST=
-
 OAUTH_FACEBOOK_APPID=FB_CL_ID
 OAUTH_FACEBOOK_SECRET=FB_CL_SECRET
 

app/cmd/routes.go

@@ -16,6 +16,7 @@ func routes(r *web.Engine) *web.Engine {
 	r.Worker().Use(middlewares.WorkerSetup())
 
 	r.Use(middlewares.CatchPanic())
+	r.Use(middlewares.Instrumentation())
 
 	r.NotFound(func(c *web.Context) error {
 		next := func(c *web.Context) error {

app/handlers/apiv1/post.go

@@ -2,6 +2,7 @@ package apiv1
 
 import (
 	"github.com/getfider/fider/app/actions"
+	"github.com/getfider/fider/app/metrics"
 	"github.com/getfider/fider/app/models/cmd"
 	"github.com/getfider/fider/app/models/entity"
 	"github.com/getfider/fider/app/models/enum"
@@ -57,6 +58,7 @@ func CreatePost() web.HandlerFunc {
 
 		c.Enqueue(tasks.NotifyAboutNewPost(newPost.Result))
 
+		metrics.TotalPosts.Inc()
 		return c.Ok(web.Map{
 			"id":     newPost.Result.ID,
 			"number": newPost.Result.Number,
@@ -250,6 +252,7 @@ func PostComment() web.HandlerFunc {
 
 		c.Enqueue(tasks.NotifyAboutNewComment(getPost.Result, action.Content))
 
+		metrics.TotalComments.Inc()
 		return c.Ok(web.Map{
 			"id": addNewComment.Result.ID,
 		})
@@ -309,9 +312,15 @@ func DeleteComment() web.HandlerFunc {
 // AddVote adds current user to given post list of votes
 func AddVote() web.HandlerFunc {
 	return func(c *web.Context) error {
-		return addOrRemove(c, func(post *entity.Post, user *entity.User) bus.Msg {
+		err := addOrRemove(c, func(post *entity.Post, user *entity.User) bus.Msg {
 			return &cmd.AddVote{Post: post, User: user}
 		})
+
+		if err == nil {
+			metrics.TotalVotes.Inc()
+		}
+
+		return err
 	}
 }
 

app/handlers/signup.go

@@ -3,6 +3,7 @@ package handlers
 import (
 	"time"
 
+	"github.com/getfider/fider/app/metrics"
 	"github.com/getfider/fider/app/models/entity"
 	"github.com/getfider/fider/app/models/enum"
 	"github.com/getfider/fider/app/models/query"
@@ -69,6 +70,7 @@ func CreateTenant() web.HandlerFunc {
 			return c.Failure(err)
 		}
 
+		metrics.TotalTenants.Inc()
 		c.SetTenant(createTenant.Result)
 
 		user := &entity.User{

app/metrics/metrics_fider.go

@@ -0,0 +1,47 @@
+package metrics
+
+import (
+	"github.com/getfider/fider/app/pkg/env"
+	"github.com/prometheus/client_golang/prometheus"
+)
+
+var TotalTenants = prometheus.NewCounter(
+	prometheus.CounterOpts{
+		Name: "fider_tenants_total",
+		Help: "Number of Fider tenants.",
+	},
+)
+
+var TotalPosts = prometheus.NewCounter(
+	prometheus.CounterOpts{
+		Name: "fider_posts_total",
+		Help: "Number of Fider posts.",
+	},
+)
+
+var TotalComments = prometheus.NewCounter(
+	prometheus.CounterOpts{
+		Name: "fider_comments_total",
+		Help: "Number of Fider comments.",
+	},
+)
+
+var TotalVotes = prometheus.NewCounter(
+	prometheus.CounterOpts{
+		Name: "fider_votes_total",
+		Help: "Number of Fider votes.",
+	},
+)
+
+var fiderInfo = prometheus.NewGauge(
+	prometheus.GaugeOpts{
+		Name:        "fider_info",
+		Help:        "Information about Fider environment.",
+		ConstLabels: prometheus.Labels{"version": env.Version()},
+	},
+)
+
+func init() {
+	fiderInfo.Inc()
+	prometheus.MustRegister(TotalTenants, TotalPosts, TotalComments, TotalVotes, fiderInfo)
+}

app/metrics/metrics_http.go

@@ -0,0 +1,21 @@
+package metrics
+
+import "github.com/prometheus/client_golang/prometheus"
+
+var HttpRequests = prometheus.NewCounterVec(
+	prometheus.CounterOpts{
+		Name: "http_requests_total",
+		Help: "Number of HTTP requests.",
+	},
+	[]string{"code", "operation"},
+)
+
+var HttpDuration = prometheus.NewHistogramVec(prometheus.HistogramOpts{
+	Name: "http_request_duration_seconds",
+	Help: "Duration of HTTP requests.",
+	Buckets: []float64{0.2, 0.5, 1, 2, 5},
+}, []string{"operation"})
+
+func init() {
+	prometheus.MustRegister(HttpRequests, HttpDuration)
+}

app/middlewares/instrumentation.go

@@ -0,0 +1,34 @@
+package middlewares
+
+import (
+	"fmt"
+	"strconv"
+	"time"
+
+	"github.com/getfider/fider/app/metrics"
+	"github.com/getfider/fider/app/pkg/env"
+	"github.com/getfider/fider/app/pkg/web"
+	"github.com/julienschmidt/httprouter"
+)
+
+// Instrumentation adds Prometheus HTTP Middlewares
+func Instrumentation() web.MiddlewareFunc {
+	if !env.Config.Metrics.Enabled {
+		return nil
+	}
+
+	return func(next web.HandlerFunc) web.HandlerFunc {
+		return func(c *web.Context) error {
+			begin := time.Now()
+
+			err := next(c)
+
+			operation := fmt.Sprintf("%s /%s", c.Request.Method, c.Param(httprouter.MatchedRoutePathParam))
+			code := strconv.Itoa(c.ResponseStatusCode)
+			metrics.HttpRequests.WithLabelValues(code, operation).Inc()
+			metrics.HttpDuration.WithLabelValues(operation).Observe(time.Since(begin).Seconds())
+
+			return err
+		}
+	}
+}

app/middlewares/instrumentation_test.go

@@ -0,0 +1,58 @@
+package middlewares_test
+
+import (
+	"net/http"
+	"testing"
+
+	"github.com/getfider/fider/app/metrics"
+	"github.com/getfider/fider/app/middlewares"
+	. "github.com/getfider/fider/app/pkg/assert"
+	"github.com/getfider/fider/app/pkg/env"
+	"github.com/getfider/fider/app/pkg/mock"
+	"github.com/getfider/fider/app/pkg/web"
+	"github.com/prometheus/client_golang/prometheus"
+	dto "github.com/prometheus/client_model/go"
+)
+
+func TestInstrumentation_Disabled(t *testing.T) {
+	RegisterT(t)
+
+	defer func() {
+		env.Config.Metrics.Enabled = true
+	}()
+
+	server := mock.NewServer()
+	env.Config.Metrics.Enabled = false
+	server.Use(middlewares.Instrumentation())
+	handler := func(c *web.Context) error {
+		return c.NoContent(http.StatusOK)
+	}
+
+	status, _ := server.Execute(handler)
+
+	Expect(status).Equals(http.StatusOK)
+	Expect(getCounterValue(metrics.HttpRequests, "200", "GET /")).Equals(float64(0))
+}
+
+func TestInstrumentation_Enabled(t *testing.T) {
+	RegisterT(t)
+
+	server := mock.NewServer()
+	server.Use(middlewares.Instrumentation())
+	handler := func(c *web.Context) error {
+		return c.NoContent(http.StatusOK)
+	}
+
+	status, _ := server.Execute(handler)
+
+	Expect(status).Equals(http.StatusOK)
+	Expect(getCounterValue(metrics.HttpRequests, "200", "GET /")).Equals(float64(1))
+}
+
+func getCounterValue(metric *prometheus.CounterVec, lvs ...string) float64 {
+	var m = &dto.Metric{}
+	if err := metric.WithLabelValues(lvs...).Write(m); err != nil {
+		return 0
+	}
+	return m.Counter.GetValue()
+}

app/middlewares/maintenance.go

@@ -9,11 +9,12 @@ import (
 
 // Maintenance returns a maintenance page when system is under maintenance
 func Maintenance() web.MiddlewareFunc {
+	if !env.Config.Maintenance.Enabled {
+		return nil
+	}
+
 	return func(next web.HandlerFunc) web.HandlerFunc {
 		return func(c *web.Context) error {
-			if !env.Config.Maintenance.Enabled {
-				return next(c)
-			}
 
 			c.Response.Header().Set("Retry-After", "3600")
 

app/pkg/env/env.go

@@ -16,7 +16,7 @@ import (
 var (
 	// these values are replaced during CI build
 	buildnumber = ""
-	version     = "0.18.1"
+	version     = "0.19.0-dev"
 )
 
 func Version() string {
@@ -40,7 +40,11 @@ type config struct {
 	HostDomain string `env:"HOST_DOMAIN,required"`
 	Locale     string `env:"LOCALE,default=en"`
 	JWTSecret  string `env:"JWT_SECRET,required"`
-	Database             struct {
+	Metrics    struct {
+		Enabled bool   `env:"METRICS_ENABLED,default=false"`
+		Port    string `env:"METRICS_PORT,default=4000"`
+	}
+	Database struct {
 		URL          string `env:"DATABASE_URL,required"`
 		MaxIdleConns int    `env:"DATABASE_MAX_IDLE_CONNS,default=2,strict"`
 		MaxOpenConns int    `env:"DATABASE_MAX_OPEN_CONNS,default=4,strict"`

app/pkg/mock/server.go

@@ -49,7 +49,9 @@ func (s *Server) Engine() *web.Engine {
 
 // Use adds a new middleware to pipeline
 func (s *Server) Use(middleware web.MiddlewareFunc) *Server {
-	s.middleware = append(s.middleware, middleware)
+	if middleware != nil {
+		s.middleware = append(s.middleware, middleware)
+	}
 	return s
 }