Feature/Implement exporter

* Added exporter structure
* Added serverPrometheus interface, serverPrometheusWrapper
* Added mocks

consts.go

@@ -3,6 +3,12 @@ package heartbeat
 import "log"
 
 const (
+	// Exporter
+	exporterStartMessage    = "Prometheus exporter started on "
+	exporterErrorMsg        = "Failed to start prometheus exporter on port "
+	exporterShutdownMessage = "Prometheus exporter is in the shutdown mode and won't accept new connections"
+	exporterStopMessage     = "Prometheus exporter stopped gracefully"
+
 	// Logger
 	infoLogLevel    = "INFO"
 	warningLogLevel = "WARNING"

exporter.go

@@ -0,0 +1,113 @@
+package heartbeat
+
+import (
+	"context"
+	"errors"
+	"net"
+	"net/http"
+	"strconv"
+	"sync"
+	"time"
+
+	"github.com/prometheus/client_golang/prometheus/promhttp"
+)
+
+// WaitGroup interface
+type waitGroup interface {
+	Add(int)
+	Done()
+	Wait()
+}
+
+// serverPrometheusWrapper structure. Used for testing purposes
+type serverPrometheusWrapper struct {
+	*http.Server
+}
+
+// serverPrometheusWrapper methods
+func (wrapper *serverPrometheusWrapper) Port() string {
+	return wrapper.Addr
+}
+
+// serverPrometheus interface
+type serverPrometheus interface {
+	ListenAndServe() error
+	Shutdown(context.Context) error
+	Port() string
+}
+
+// Exporter structure
+type exporter struct {
+	server          serverPrometheus
+	shutdownTimeout time.Duration
+	err             error
+	route           string
+	ctx             context.Context
+	wg              waitGroup
+	logger          logger
+}
+
+// Exporter builder. Returns pointer to new exporter structure
+func newExporter(port, shutdownTimeout int, route string, logger logger) *exporter {
+	handler := http.NewServeMux()
+	handler.Handle(route, promhttp.Handler())
+
+	return &exporter{
+		server: &serverPrometheusWrapper{
+			Server: &http.Server{
+				Addr:    ":" + strconv.Itoa(port),
+				Handler: handler,
+			},
+		},
+		logger:          logger,
+		shutdownTimeout: time.Duration(shutdownTimeout),
+		route:           route,
+	}
+}
+
+// Exporter methods
+
+// Starts exporter, runs listen channel from the parent (heartbeat server)
+func (exporter *exporter) start(parentContext context.Context, wg *sync.WaitGroup) error {
+	exporter.ctx, exporter.wg = parentContext, wg
+	exporter.listenShutdownSignal()
+	exporter.logger.info(exporterStartMessage + exporter.server.Port() + exporter.route)
+
+	return exporter.server.ListenAndServe()
+}
+
+// Stops exporter with timeout
+func (exporter *exporter) stop() error {
+	ctx, cancel := context.WithTimeout(exporter.ctx, exporter.shutdownTimeout*time.Second)
+	defer cancel()
+
+	return exporter.server.Shutdown(ctx)
+}
+
+// Exporter shutdown signal listener. Stops exporter by shutdown signal
+func (exporter *exporter) listenShutdownSignal() {
+	go func() {
+		defer exporter.wg.Done()
+		exporterLogger := exporter.logger
+
+		<-exporter.ctx.Done()
+		exporterLogger.warning(exporterShutdownMessage)
+		if err := exporter.stop(); err != nil {
+			exporter.err = err
+		}
+
+		exporterLogger.info(exporterStopMessage)
+	}()
+}
+
+// Exporter port-for-bind checker
+func (exporter *exporter) isPortAvailable() (err error) {
+	port := exporter.server.Port()
+	listener, err := net.Listen("tcp", port)
+	if err != nil {
+		return errors.New(exporterErrorMsg + port)
+	}
+
+	listener.Close()
+	return
+}

exporter_test.go

@@ -0,0 +1,107 @@
+package heartbeat
+
+import (
+	"context"
+	"net"
+	"strconv"
+	"sync"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/mock"
+)
+
+func TestNewExporter(t *testing.T) {
+	t.Run("creates new exporter", func(t *testing.T) {
+		port, shutdownTimeout, route, logger := 8080, 42, "/some_route", newLogger(false, false)
+		exporter := newExporter(port, shutdownTimeout, route, logger)
+
+		assert.Equal(t, logger, exporter.logger)
+		assert.Equal(t, time.Duration(shutdownTimeout), exporter.shutdownTimeout)
+		assert.Equal(t, ":"+strconv.Itoa(port), exporter.server.Port())
+		assert.Equal(t, route, exporter.route)
+	})
+}
+
+func TestExporterStart(t *testing.T) {
+	t.Run("starts exporter server", func(t *testing.T) {
+		prometheusServer, logger := new(serverPrometheusMock), new(loggerMock)
+		port, route, parentContext, wg := ":8080", "/some_route", context.Background(), new(sync.WaitGroup)
+		exporter := &exporter{
+			server: prometheusServer,
+			logger: logger,
+			route:  route,
+		}
+		prometheusServer.On("Port").Once().Return(port)
+		logger.On("info", []string{exporterStartMessage + port + route}).Once().Return(nil)
+		prometheusServer.On("ListenAndServe").Once().Return(nil)
+
+		assert.NoError(t, exporter.start(parentContext, wg))
+		assert.Equal(t, parentContext, exporter.ctx)
+		assert.Equal(t, wg, exporter.wg)
+	})
+}
+
+func TestExporterStop(t *testing.T) {
+	t.Run("stops exporter server", func(t *testing.T) {
+		prometheusServer := new(serverPrometheusMock)
+		exporter := &exporter{
+			server:          prometheusServer,
+			ctx:             context.Background(),
+			shutdownTimeout: time.Duration(2),
+		}
+		prometheusServer.On("Shutdown", mock.AnythingOfType("*context.timerCtx")).Once().Return(nil)
+
+		assert.NoError(t, exporter.stop())
+	})
+}
+
+func TestListenShutdownSignal(t *testing.T) {
+	t.Run("listens shutdown signal", func(t *testing.T) {
+		prometheusServer, logger, wg := new(serverPrometheusMock), new(loggerMock), &sync.WaitGroup{}
+		parentContext, cancel := context.WithCancel(context.Background())
+		exporter := &exporter{
+			server:          prometheusServer,
+			logger:          logger,
+			ctx:             parentContext,
+			wg:              wg,
+			shutdownTimeout: time.Duration(2),
+		}
+
+		wg.Add(1) // Add 1 to the wait group
+		logger.On("warning", []string{exporterShutdownMessage}).Once().Return(nil)
+		logger.On("info", []string{exporterStopMessage}).Once().Return(nil)
+		prometheusServer.On("Shutdown", mock.AnythingOfType("*context.timerCtx")).Once().Return(nil)
+		exporter.listenShutdownSignal()
+		cancel()  // Simulate shutdown signal
+		wg.Wait() // Wait for goroutine to finish
+
+		assert.Nil(t, exporter.err)
+	})
+}
+
+func TestIsPortAvailable(t *testing.T) {
+	prometheusServer, port := new(serverPrometheusMock), ":8282"
+	t.Run("checks if port is available", func(t *testing.T) {
+		exporter := &exporter{
+			server: prometheusServer,
+			logger: new(loggerMock),
+		}
+		prometheusServer.On("Port").Once().Return(port)
+
+		assert.NoError(t, exporter.isPortAvailable())
+	})
+
+	t.Run("checks if port is unavailable", func(t *testing.T) {
+		exporter := &exporter{
+			server: prometheusServer,
+			logger: new(loggerMock),
+		}
+		prometheusServer.On("Port").Once().Return(port)
+		listener, _ := net.Listen("tcp", port)
+		defer listener.Close()
+
+		assert.Error(t, exporter.isPortAvailable(), exporterErrorMsg+port)
+	})
+}

go.mod

@@ -3,11 +3,23 @@ module heartbeat
 go 1.23.0
 
 require (
+	github.com/prometheus/client_golang v1.20.3
 	github.com/stretchr/testify v1.9.0
 	gopkg.in/yaml.v3 v3.0.1
 )
 
 require (
+	github.com/beorn7/perks v1.0.1 // indirect
+	github.com/cespare/xxhash/v2 v2.3.0 // indirect
 	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/klauspost/compress v1.17.9 // indirect
+	github.com/kr/text v0.2.0 // indirect
+	github.com/munnerz/goautoneg v0.0.0-20191010083416-a7dc8b61c822 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
+	github.com/prometheus/client_model v0.6.1 // indirect
+	github.com/prometheus/common v0.59.1 // indirect
+	github.com/prometheus/procfs v0.15.1 // indirect
+	github.com/stretchr/objx v0.5.2 // indirect
+	golang.org/x/sys v0.25.0 // indirect
+	google.golang.org/protobuf v1.34.2 // indirect
 )

go.sum

@@ -1,10 +1,44 @@
+github.com/beorn7/perks v1.0.1 h1:VlbKKnNfV8bJzeqoa4cOKqO6bYr3WgKZxO8Z16+hsOM=
+github.com/beorn7/perks v1.0.1/go.mod h1:G2ZrVWU2WbWT9wwq4/hrbKbnv/1ERSJQ0ibhJ6rlkpw=
+github.com/cespare/xxhash/v2 v2.3.0 h1:UL815xU9SqsFlibzuggzjXhog7bL6oX9BbNZnL2UFvs=
+github.com/cespare/xxhash/v2 v2.3.0/go.mod h1:VGX0DQ3Q6kWi7AoAeZDth3/j3BFtOZR5XLFGgcrjCOs=
+github.com/creack/pty v1.1.9/go.mod h1:oKZEueFk5CKHvIhNR5MUki03XCEU+Q6VDXinZuGJ33E=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/google/go-cmp v0.6.0 h1:ofyhxvXcZhMsU5ulbFiLKl/XBFqE1GSq7atu8tAmTRI=
+github.com/google/go-cmp v0.6.0/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
+github.com/klauspost/compress v1.17.9 h1:6KIumPrER1LHsvBVuDa0r5xaG0Es51mhhB9BQB2qeMA=
+github.com/klauspost/compress v1.17.9/go.mod h1:Di0epgTjJY877eYKx5yC51cX2A2Vl2ibi7bDH9ttBbw=
+github.com/kr/pretty v0.3.1 h1:flRD4NNwYAUpkphVc1HcthR4KEIFJ65n8Mw5qdRn3LE=
+github.com/kr/pretty v0.3.1/go.mod h1:hoEshYVHaxMs3cyo3Yncou5ZscifuDolrwPKZanG3xk=
+github.com/kr/text v0.2.0 h1:5Nx0Ya0ZqY2ygV366QzturHI13Jq95ApcVaJBhpS+AY=
+github.com/kr/text v0.2.0/go.mod h1:eLer722TekiGuMkidMxC/pM04lWEeraHUUmBw8l2grE=
+github.com/kylelemons/godebug v1.1.0 h1:RPNrshWIDI6G2gRW9EHilWtl7Z6Sb1BR0xunSBf0SNc=
+github.com/kylelemons/godebug v1.1.0/go.mod h1:9/0rRGxNHcop5bhtWyNeEfOS8JIWk580+fNqagV/RAw=
+github.com/munnerz/goautoneg v0.0.0-20191010083416-a7dc8b61c822 h1:C3w9PqII01/Oq1c1nUAm88MOHcQC9l5mIlSMApZMrHA=
+github.com/munnerz/goautoneg v0.0.0-20191010083416-a7dc8b61c822/go.mod h1:+n7T8mK8HuQTcFwEeznm/DIxMOiR9yIdICNftLE1DvQ=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/prometheus/client_golang v1.20.3 h1:oPksm4K8B+Vt35tUhw6GbSNSgVlVSBH0qELP/7u83l4=
+github.com/prometheus/client_golang v1.20.3/go.mod h1:PIEt8X02hGcP8JWbeHyeZ53Y/jReSnHgO035n//V5WE=
+github.com/prometheus/client_model v0.6.1 h1:ZKSh/rekM+n3CeS952MLRAdFwIKqeY8b62p8ais2e9E=
+github.com/prometheus/client_model v0.6.1/go.mod h1:OrxVMOVHjw3lKMa8+x6HeMGkHMQyHDk9E3jmP2AmGiY=
+github.com/prometheus/common v0.59.1 h1:LXb1quJHWm1P6wq/U824uxYi4Sg0oGvNeUm1z5dJoX0=
+github.com/prometheus/common v0.59.1/go.mod h1:GpWM7dewqmVYcd7SmRaiWVe9SSqjf0UrwnYnpEZNuT0=
+github.com/prometheus/procfs v0.15.1 h1:YagwOFzUgYfKKHX6Dr+sHT7km/hxC76UB0learggepc=
+github.com/prometheus/procfs v0.15.1/go.mod h1:fB45yRUv8NstnjriLhBQLuOUt+WW4BsoGhij/e3PBqk=
+github.com/rogpeppe/go-internal v1.10.0 h1:TMyTOH3F/DB16zRVcYyreMH6GnZZrwQVAoYjRBZyWFQ=
+github.com/rogpeppe/go-internal v1.10.0/go.mod h1:UQnix2H7Ngw/k4C5ijL5+65zddjncjaFoBhdsK/akog=
+github.com/stretchr/objx v0.5.2 h1:xuMeJ0Sdp5ZMRXx/aWO6RZxdr3beISkG5/G/aIRr3pY=
+github.com/stretchr/objx v0.5.2/go.mod h1:FRsXN1f5AsAjCGJKqEizvkpNtU+EGNCLh3NxZ/8L+MA=
 github.com/stretchr/testify v1.9.0 h1:HtqpIVDClZ4nwg75+f6Lvsy/wHu+3BoSGCbBAcpTsTg=
 github.com/stretchr/testify v1.9.0/go.mod h1:r2ic/lqez/lEtzL7wO/rwa5dbSLXVDPFyf8C91i36aY=
-gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
+golang.org/x/sys v0.25.0 h1:r+8e+loiHxRqhXVl6ML1nO3l1+oFoWbnlu2Ehimmi34=
+golang.org/x/sys v0.25.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
+google.golang.org/protobuf v1.34.2 h1:6xV6lTsCfpGD21XK49h7MhtcApnLqkfYgPcdHftf6hg=
+google.golang.org/protobuf v1.34.2/go.mod h1:qYOHts0dSfpeUzUFpOMr/WGzszTmLH+DiWniOlNbLDw=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c h1:Hei/4ADfdWqJk1ZMxUNpqntNwaWcugrBjAiHlqqRiVk=
+gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c/go.mod h1:JHkPIbrfpd72SG/EVd6muEfDQjcINNoR0C8j2r3qZ4Q=
 gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
 gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

logger.go

@@ -6,14 +6,13 @@ import (
 	"os"
 )
 
-// TODO: uncomment when this logger will embedded as interface
-// // Logger interface
-// type logger interface {
-// 	infoActivity(...string)
-// 	info(...string)
-// 	warning(...string)
-// 	error(...string)
-// }
+// Logger interface
+type logger interface {
+	infoActivity(...string)
+	info(...string)
+	warning(...string)
+	error(...string)
+}
 
 // Custom logger that supports 3 different log levels (info, warning, error)
 type eventLogger struct {

test_helpers_test.go

@@ -1,6 +1,8 @@
 package heartbeat
 
-import "regexp"
+import (
+	"regexp"
+)
 
 // Regex builder
 func newRegex(regexPattern string) (*regexp.Regexp, error) {