OpenTelemetry plugin (#155)

* Finish OpenTelemetry plugin

* Fix CI

Makefile

@@ -20,6 +20,7 @@ PLUGINS=\
 	docs \
 	goakit \
 	i18n \
+	otel \
 	types \
 	zaplogger \
 	zerologger

go.mod

@@ -6,17 +6,20 @@ require (
 	github.com/go-kit/kit v0.13.0
 	github.com/go-kit/log v0.2.1
 	github.com/gorilla/websocket v1.5.1
+	github.com/stretchr/testify v1.8.4
 	go.uber.org/zap v1.26.0
 	goa.design/goa/v3 v3.14.6
 )
 
 require (
 	github.com/AnatolyRugalev/goregen v0.1.0 // indirect
+	github.com/davecgh/go-spew v1.1.1 // indirect
 	github.com/dimfeld/httppath v0.0.0-20170720192232-ee938bf73598 // indirect
 	github.com/go-chi/chi/v5 v5.0.11 // indirect
 	github.com/go-logfmt/logfmt v0.5.1 // indirect
 	github.com/google/uuid v1.5.0 // indirect
 	github.com/manveru/faker v0.0.0-20171103152722-9fbc68a78c4d // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
 	github.com/sergi/go-diff v1.3.1 // indirect
 	go.uber.org/multierr v1.10.0 // indirect
 	golang.org/x/mod v0.14.0 // indirect

otel/Makefile

@@ -0,0 +1,10 @@
+#! /usr/bin/make
+#
+# Makefile for Goa otel plugin
+
+# include common Makefile content for plugins
+GOPATH=$(shell go env GOPATH)
+include ../plugins.mk
+
+# Make CI happy
+gen:

otel/README.md

@@ -1,7 +1,9 @@
 # OpenTelemetry Plugin
 
 The `otel` plugin is a [Goa](https://github.com/goadesign/goa/tree/v3) plugin that instruments
-HTTP endpoints with OpenTelemetry configuring it with the endpoint route pattern.
+HTTP endpoints with OpenTelemetry configuring it with the endpoint route pattern. This
+plugin is used in conjunction with the [Clue](https://github.com/goadesign/clue) project to
+instrument services with OpenTelemetry.
 
 ## Usage
 
@@ -30,3 +32,53 @@ where `PACKAGE` is the Go import path of the design package.
 Importing the `otel` package changes the behavior of the `gen` command of the
 `goa` tool. The `gen` command output is modified so that the generated HTTP
 handlers are wrapped with a call to the `otelhttp.WithRouteTag`
+
+## OpenTelemetry Configuration
+
+For the code generated by the plugin to work the OpenTelemetry SDK must be
+initialized. This can be done by importing the `clue` package and calling
+`clue.ConfigureOpenTelemetry` in the `main` function of the service:
+
+```go
+package main
+
+import (
+	"context"
+	"net/http"
+
+	"go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp"
+	"go.opentelemetry.io/otel/exporters/stdout/stdoutmetric"
+	"go.opentelemetry.io/otel/exporters/stdout/stdouttrace"
+	"goa.design/clue/clue"
+	"goa.design/clue/log"
+)
+
+func main() {
+	// Create OpenTelemetry metric and span exporters
+	// Use stdout exporters for demo.
+	metricExporter, err := stdoutmetric.New()
+	if err != nil {
+		panic(err)
+	}
+	spanExporter, err := stdouttrace.New()
+	if err != nil {
+		panic(err)
+	}
+
+	// Configure OpenTelemetry.
+	ctx := log.Context(context.Background())
+	cfg, err := clue.NewConfig(ctx, "service", "1.0.0", metricExporter, spanExporter)
+	if err != nil {
+		panic(err)
+	}
+	clue.ConfigureOpenTelemetry(ctx, cfg)
+
+	// Create HTTP handler and start server.
+	var handler http.Handler = http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Write([]byte("Hello, World!"))
+	})
+	handler = otelhttp.NewHandler(handler, "service") // Instrument handler.
+	http.ListenAndServe(":8080", handler)
+}
+```
+

otel/generate.go

@@ -21,9 +21,8 @@ func Generate(genpkg string, roots []eval.Root, files []*codegen.File) ([]*codeg
 				if s.Name == "server-handler" {
 					s.Source = strings.Replace(
 						s.Source,
-						"{{- range Routes }}",
-						`f = otelhttp.WithRouteTag("{{ .Path }}", f).ServeHTTP
-						 {{- range Routes }}`,
+						`mux.Handle("{{ .Verb }}", "{{ .Path }}", f)`,
+						`mux.Handle("{{ .Verb }}", "{{ .Path }}", otelhttp.WithRouteTag("{{ .Path }}", f).ServeHTTP)`,
 						1,
 					)
 				}

otel/generate_test.go

@@ -0,0 +1,50 @@
+package otel
+
+import (
+	"bytes"
+	"flag"
+	"fmt"
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"goa.design/goa/v3/codegen"
+	"goa.design/goa/v3/eval"
+	httpcodegen "goa.design/goa/v3/http/codegen"
+	"goa.design/plugins/v3/otel/testdata"
+)
+
+var update = flag.Bool("update", false, "update golden files")
+
+func TestOtel(t *testing.T) {
+	cases := []struct {
+		Name string
+		DSL  func()
+	}{
+		{"one route", testdata.OneRoute},
+		{"multiple routes", testdata.MultipleRoutes},
+	}
+	for _, c := range cases {
+		t.Run(c.Name, func(t *testing.T) {
+			root := codegen.RunDSL(t, c.DSL)
+			serverFiles := httpcodegen.ServerFiles("gen", root)
+			require.Len(t, serverFiles, 2)
+			fs, err := Generate("", []eval.Root{root}, serverFiles)
+			assert.NoError(t, err)
+			require.Len(t, fs, 2)
+			sections := fs[0].Section("server-handler")
+			require.Len(t, sections, 1)
+			section := sections[0]
+			var buf bytes.Buffer
+			assert.NoError(t, section.Write(&buf))
+			golden := filepath.Join("testdata", fmt.Sprintf("%s.golden", c.Name))
+			if *update {
+				assert.NoError(t, os.WriteFile(golden, buf.Bytes(), 0644))
+			}
+			expected, _ := os.ReadFile(golden)
+			assert.Equal(t, buf.String(), string(expected))
+		})
+	}
+}

otel/testdata/dsls.go

@@ -0,0 +1,28 @@
+package testdata
+
+import (
+	. "goa.design/goa/v3/dsl"
+	_ "goa.design/plugins/v3/docs"
+)
+
+var OneRoute = func() {
+	Service("Service", func() {
+		Method("Method", func() {
+			HTTP(func() {
+				GET("/")
+			})
+		})
+	})
+}
+
+var MultipleRoutes = func() {
+	Service("Service2", func() {
+		Method("Method", func() {
+			HTTP(func() {
+				GET("/")
+				GET("/other")
+			})
+			GRPC(func() {})
+		})
+	})
+}

otel/testdata/multiple routes.golden

@@ -0,0 +1,12 @@
+// MountMethodHandler configures the mux to serve the "Service2" service
+// "Method" endpoint.
+func MountMethodHandler(mux goahttp.Muxer, h http.Handler) {
+	f, ok := h.(http.HandlerFunc)
+	if !ok {
+		f = func(w http.ResponseWriter, r *http.Request) {
+			h.ServeHTTP(w, r)
+		}
+	}
+	mux.Handle("GET", "/", otelhttp.WithRouteTag("/", f).ServeHTTP)
+	mux.Handle("GET", "/other", otelhttp.WithRouteTag("/other", f).ServeHTTP)
+}

otel/testdata/one route.golden

@@ -0,0 +1,11 @@
+// MountMethodHandler configures the mux to serve the "Service" service
+// "Method" endpoint.
+func MountMethodHandler(mux goahttp.Muxer, h http.Handler) {
+	f, ok := h.(http.HandlerFunc)
+	if !ok {
+		f = func(w http.ResponseWriter, r *http.Request) {
+			h.ServeHTTP(w, r)
+		}
+	}
+	mux.Handle("GET", "/", otelhttp.WithRouteTag("/", f).ServeHTTP)
+}