Instrumentation

.gitignore

@@ -2,3 +2,4 @@
 /*.iml
 /go-demo
 /docker/registry/
+/tmp

Dockerfile.big

@@ -1,4 +1,4 @@
-FROM golang:1.6 AS build
+FROM golang:1.7 AS build
 ADD . /src
 WORKDIR /src
 RUN go get -d -v -t

Dockerfile.multistage

@@ -1,4 +1,4 @@
-FROM golang:1.6 AS build
+FROM golang:1.7 AS build
 ADD . /src
 WORKDIR /src
 RUN go get -d -v -t

integration_test.go

@@ -33,7 +33,7 @@ import (
 
 type IntegrationTestSuite struct {
 	suite.Suite
-	hostIp      string
+	hostIp string
 }
 
 func (s *IntegrationTestSuite) SetupTest() {

main.go

@@ -1,37 +1,46 @@
 package main
 
 import (
+	"fmt"
+	"github.com/prometheus/client_golang/prometheus"
 	"gopkg.in/mgo.v2"
+	"gopkg.in/mgo.v2/bson"
 	"io"
 	"log"
+	"math/rand"
 	"net/http"
 	"os"
 	"strconv"
-	"time"
-	"gopkg.in/mgo.v2/bson"
-	"fmt"
 	"strings"
-	"math/rand"
+	"time"
 )
 
 var coll *mgo.Collection
 var sleep = time.Sleep
 var logFatal = log.Fatal
 var logPrintf = log.Printf
-var httpHandleFunc = http.HandleFunc
 var httpListenAndServe = http.ListenAndServe
 
 type Person struct {
 	Name string
 }
 
-// TODO: Test
+var (
+	histogram = prometheus.NewHistogramVec(prometheus.HistogramOpts{
+		Name: "resp_time",
+		Help: "Request response time",
+	}, []string{"code", "method", "path", "query"})
+)
 
 func main() {
 	setupDb()
 	RunServer()
 }
 
+func init() {
+	prometheus.MustRegister(histogram)
+}
+
 // TODO: Test
 
 func setupDb() {
@@ -47,13 +56,18 @@ func setupDb() {
 }
 
 func RunServer() {
-	httpHandleFunc("/demo/hello", HelloServer)
-	httpHandleFunc("/demo/person", PersonServer)
-	httpHandleFunc("/demo/random-error", RandomErrorServer)
-	logFatal("ListenAndServe: ", httpListenAndServe(":8080", nil))
+	mux := http.NewServeMux()
+	mux.HandleFunc("/demo/hello", HelloServer)
+	mux.HandleFunc("/demo/person", PersonServer)
+	mux.HandleFunc("/demo/random-error", RandomErrorServer)
+	mux.Handle("/metrics", prometheusHandler())
+	logFatal("ListenAndServe: ", httpListenAndServe(":8080", mux))
 }
 
 func HelloServer(w http.ResponseWriter, req *http.Request) {
+	start := time.Now()
+	defer func() { recordMetrics(start, req, http.StatusOK) }()
+
 	logPrintf("%s request to %s\n", req.Method, req.RequestURI)
 	delay := req.URL.Query().Get("delay")
 	if len(delay) > 0 {
@@ -64,28 +78,37 @@ func HelloServer(w http.ResponseWriter, req *http.Request) {
 }
 
 func RandomErrorServer(w http.ResponseWriter, req *http.Request) {
+	code := http.StatusOK
+	start := time.Now()
+	defer func() { recordMetrics(start, req, code) }()
+
 	logPrintf("%s request to %s\n", req.Method, req.RequestURI)
 	rand.Seed(time.Now().UnixNano())
 	n := rand.Intn(10)
+	msg := "Everything is still OK\n"
 	if n == 0 {
-		w.WriteHeader(http.StatusInternalServerError)
-		msg := "ERROR: Something, somewhere, went wrong!\n"
+		code = http.StatusInternalServerError
+		msg = "ERROR: Something, somewhere, went wrong!\n"
 		logPrintf(msg)
-		io.WriteString(w, msg)
-	} else {
-		io.WriteString(w, "Everything is still OK\n")
 	}
+	w.WriteHeader(code)
+	io.WriteString(w, msg)
 }
 
 func PersonServer(w http.ResponseWriter, req *http.Request) {
-	logPrintf("%s request to %s\n", req.Method, req.RequestURI)
+	code := http.StatusOK
+	start := time.Now()
+	defer func() { recordMetrics(start, req, code) }()
 
+	logPrintf("%s request to %s\n", req.Method, req.RequestURI)
+	msg := "Everything is OK"
 	if req.Method == "PUT" {
 		name := req.URL.Query().Get("name")
 		if _, err := upsertId(name, &Person{
 			Name: name,
 		}); err != nil {
-			panic(err)
+			code = http.StatusInternalServerError
+			msg = err.Error()
 		}
 	} else {
 		var res []Person
@@ -95,10 +118,15 @@ func PersonServer(w http.ResponseWriter, req *http.Request) {
 		var names []string
 		for _, p := range res {
 			names = append(names, p.Name)
-			io.WriteString(w, fmt.Sprintln(p.Name))
 		}
-		io.WriteString(w, strings.Join(names, "\n"))
+		msg = strings.Join(names, "\n")
 	}
+	w.WriteHeader(code)
+	io.WriteString(w, msg)
+}
+
+var prometheusHandler = func() http.Handler {
+	return prometheus.Handler()
 }
 
 var findPeople = func(res *[]Person) error {
@@ -109,3 +137,14 @@ var upsertId = func(id interface{}, update interface{}) (info *mgo.ChangeInfo, e
 	return coll.UpsertId(id, update)
 }
 
+func recordMetrics(start time.Time, req *http.Request, code int) {
+	duration := time.Since(start)
+	histogram.With(
+		prometheus.Labels{
+			"code": fmt.Sprintf("%d", code),
+			"method": req.Method,
+			"path": req.URL.Path,
+			"query": req.URL.RawQuery,
+		},
+	).Observe(duration.Seconds())
+}

main_test.go

@@ -8,65 +8,42 @@ import (
 	"net/http"
 	"testing"
 	"time"
-	"reflect"
 )
 
-// Setup
+// Suite
 
 type MainTestSuite struct {
 	suite.Suite
 }
 
-func (s *MainTestSuite) SetupTest() {
-}
-
-// RunServer
-
-func (s *MainTestSuite) Test_RunServer_InvokesHandleFuncWithHelloServer() {
-	httpHandleFuncOrig := httpHandleFunc
-	defer func() { httpHandleFunc = httpHandleFuncOrig }()
-	wasCalled := false
-	httpHandleFunc = func(pattern string, handler func(http.ResponseWriter, *http.Request)) {
-		if pattern == "/demo/hello" && reflect.ValueOf(handler) == reflect.ValueOf(HelloServer) {
-			wasCalled = true
-		}
-	}
-
-	RunServer()
+// Suite
 
-	s.True(wasCalled)
+func TestMainSuite(t *testing.T) {
+	logFatalOrig := logFatal
+	logPrintfOrig := logPrintf
+	httpListenAndServeOrig := httpListenAndServe
+	defer func() {
+		logFatal = logFatalOrig
+		logPrintf = logPrintfOrig
+		httpListenAndServe = httpListenAndServeOrig
+	}()
+	logFatal = func(v ...interface{}) {}
+	logPrintf = func(format string, v ...interface{}) {}
+	httpListenAndServe = func(addr string, handler http.Handler) error { return nil }
+	suite.Run(t, new(MainTestSuite))
 }
 
-func (s *MainTestSuite) Test_RunServer_InvokesHandleFuncWithPersonServer() {
-	httpHandleFuncOrig := httpHandleFunc
-	defer func() { httpHandleFunc = httpHandleFuncOrig }()
-	wasCalled := false
-	httpHandleFunc = func(pattern string, handler func(http.ResponseWriter, *http.Request)) {
-		if pattern == "/demo/person" && reflect.ValueOf(handler) == reflect.ValueOf(PersonServer) {
-			wasCalled = true
-		}
-	}
 
-	RunServer()
+func (s *MainTestSuite) SetupTest() {}
 
-	s.True(wasCalled)
-}
+// init
 
-func (s *MainTestSuite) Test_RunServer_InvokesHandleFuncWithRandomErrorServer() {
-	httpHandleFuncOrig := httpHandleFunc
-	defer func() { httpHandleFunc = httpHandleFuncOrig }()
-	wasCalled := false
-	httpHandleFunc = func(pattern string, handler func(http.ResponseWriter, *http.Request)) {
-		if pattern == "/demo/random-error" && reflect.ValueOf(handler) == reflect.ValueOf(RandomErrorServer) {
-			wasCalled = true
-		}
-	}
-
-	RunServer()
-
-	s.True(wasCalled)
+func (s *MainTestSuite) Test_SetupMetrics_InitializesHistogram() {
+	s.NotNil(histogram)
 }
 
+// RunServer
+
 func (s *MainTestSuite) Test_RunServer_InvokesListenAndServe() {
 	actual := ""
 	httpListenAndServe = func(addr string, handler http.Handler) error {
@@ -160,14 +137,16 @@ func (s *MainTestSuite) Test_PersonServer_Panics_WhenUpsertIdReturnsError() {
 	req, _ := http.NewRequest("PUT", "/demo/person?name=Viktor", nil)
 	w := getResponseWriterMock()
 
-	s.Panics(func() { PersonServer(w, req) })
+	PersonServer(w, req)
+
+	w.AssertCalled(s.T(), "Write", []byte("This is an error"))
 }
 
 func (s *MainTestSuite) Test_PersonServer_WritesPeople() {
 	findPeopleOrig := findPeople
 	people := []Person{
-		Person{Name: "Viktor"},
-		Person{Name: "Sara"},
+		{Name: "Viktor"},
+		{Name: "Sara"},
 	}
 	defer func() { findPeople = findPeopleOrig }()
 	findPeople = func(res *[]Person) error {
@@ -194,21 +173,6 @@ func (s *MainTestSuite) Test_PersonServer_Panics_WhenFindReturnsError() {
 	s.Panics(func() { PersonServer(w, req) })
 }
 
-// Suite
-
-func TestMainSuite(t *testing.T) {
-	logFatalOrig := logFatal
-	defer func() { logFatal = logFatalOrig }()
-	logFatal = func(v ...interface{}) {}
-	logPrintfOrig := logPrintf
-	defer func() { logPrintf = logPrintfOrig }()
-	logPrintf = func(format string, v ...interface{}) {}
-	httpListenAndServeOrig := httpListenAndServe
-	defer func() { httpListenAndServe = httpListenAndServeOrig }()
-	httpListenAndServe = func(addr string, handler http.Handler) error { return nil }
-	suite.Run(t, new(MainTestSuite))
-}
-
 type ResponseWriterMock struct {
 	mock.Mock
 }

production_test.go

@@ -7,14 +7,14 @@ import (
 	"github.com/stretchr/testify/suite"
 	"net/http"
 	"os"
+	"strconv"
 	"testing"
 	"time"
-	"strconv"
 )
 
 type ProductionTestSuite struct {
 	suite.Suite
-	hostIp      string
+	hostIp string
 }
 
 func (s *ProductionTestSuite) SetupTest() {