main_test.go

// Licensed to Elasticsearch B.V. under one or more contributor
// license agreements. See the NOTICE file distributed with
// this work for additional information regarding copyright
// ownership. Elasticsearch B.V. licenses this file to you under
// the Apache License, Version 2.0 (the "License"); you may
// not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied.  See the License for the
// specific language governing permissions and limitations
// under the License.

package main

import (
	"bytes"
	"context"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"net/http/httptest"
	"os"
	"regexp"
	"strconv"
	"strings"
	"sync"
	"testing"
	"time"

	"github.com/elastic/apm-aws-lambda/app"
	e2eTesting "github.com/elastic/apm-aws-lambda/e2e-testing"
	"github.com/elastic/apm-aws-lambda/extension"
	"github.com/elastic/apm-aws-lambda/logger"
	"github.com/elastic/apm-aws-lambda/logsapi"

	"github.com/google/uuid"
	"github.com/stretchr/testify/assert"
	"github.com/stretchr/testify/require"
	"go.uber.org/zap"
	"go.uber.org/zap/zapcore"
)

type MockEventType string

const (
	InvokeHang                         MockEventType = "Hang"
	InvokeStandard                     MockEventType = "Standard"
	InvokeStandardInfo                 MockEventType = "StandardInfo"
	InvokeStandardFlush                MockEventType = "StandardFlush"
	InvokeLateFlush                    MockEventType = "LateFlush"
	InvokeWaitgroupsRace               MockEventType = "InvokeWaitgroupsRace"
	InvokeMultipleTransactionsOverload MockEventType = "MultipleTransactionsOverload"
	Shutdown                           MockEventType = "Shutdown"
)

type MockServerInternals struct {
	Data                string
	WaitForUnlockSignal bool
	UnlockSignalChannel chan struct{}
	WaitGroup           sync.WaitGroup
}

type APMServerBehavior string

const (
	TimelyResponse APMServerBehavior = "TimelyResponse"
	SlowResponse   APMServerBehavior = "SlowResponse"
	Hangs          APMServerBehavior = "Hangs"
	Crashes        APMServerBehavior = "Crashes"
)

type MockEvent struct {
	Type              MockEventType
	APMServerBehavior APMServerBehavior
	ExecutionDuration float64
	Timeout           float64
}

type ApmInfo struct {
	BuildDate    time.Time `json:"build_date"`
	BuildSHA     string    `json:"build_sha"`
	PublishReady bool      `json:"publish_ready"`
	Version      string    `json:"version"`
}

const timeout = 20 * time.Second

func newMockApmServer(t *testing.T, l *zap.SugaredLogger) (*MockServerInternals, *httptest.Server) {
	var apmServerInternals MockServerInternals
	apmServerInternals.WaitForUnlockSignal = true
	apmServerInternals.UnlockSignalChannel = make(chan struct{})
	apmServerMutex := &sync.Mutex{}
	apmServer := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		decompressedBytes, err := e2eTesting.GetDecompressedBytesFromRequest(r)
		if err != nil {
			l.Debugf("failed to read decompressedBytes: %v", err)
			w.WriteHeader(http.StatusInternalServerError)
			return
		}

		sp := bytes.Split(decompressedBytes, []byte("\n"))
		for i := 0; i < len(sp); i++ {
			expectedBehavior := APMServerBehavior(sp[i])
			l.Debugf("Event type received by mock APM server : %s", string(expectedBehavior))
			switch expectedBehavior {
			case TimelyResponse:
				l.Debug("Timely response signal received")
			case SlowResponse:
				l.Debug("Slow response signal received")
				time.Sleep(2 * time.Second)
			case Hangs:
				l.Debug("Hang signal received")
				apmServerMutex.Lock()
				if apmServerInternals.WaitForUnlockSignal {
					<-apmServerInternals.UnlockSignalChannel
					apmServerInternals.WaitForUnlockSignal = false
				}
				apmServerMutex.Unlock()
			case Crashes:
				panic("Server crashed")
			default:
			}
		}

		if r.RequestURI == "/intake/v2/events" {
			apmServerInternals.Data += string(decompressedBytes)
			l.Debug("APM Payload processed")
			w.WriteHeader(http.StatusAccepted)
		} else if r.RequestURI == "/" {
			infoPayload, err := json.Marshal(ApmInfo{
				BuildDate:    time.Now(),
				BuildSHA:     "7814d524d3602e70b703539c57568cba6964fc20",
				PublishReady: true,
				Version:      "8.1.2",
			})
			if err != nil {
				l.Debugf("failed to marshal payload: %v", err)
				w.WriteHeader(http.StatusInternalServerError)
				return
			}

			if _, err = w.Write(infoPayload); err != nil {
				l.Debugf("failed to write payload: %v", err)
				return
			}
		}
	}))

	t.Setenv("ELASTIC_APM_LAMBDA_APM_SERVER", apmServer.URL)
	t.Setenv("ELASTIC_APM_SECRET_TOKEN", "none")

	t.Cleanup(func() { apmServer.Close() })
	return &apmServerInternals, apmServer
}

func newMockLambdaServer(t *testing.T, logsapiAddr string, eventsChannel chan MockEvent, l *zap.SugaredLogger) *MockServerInternals {
	var lambdaServerInternals MockServerInternals
	// A big queue that can hold all the events required for a test
	mockLogEventQ := make(chan logsapi.LogEvent, 100)
	ctx, cancel := context.WithCancel(context.Background())

	var wg sync.WaitGroup
	wg.Add(1)
	go func() {
		defer wg.Done()
		startLogSender(ctx, mockLogEventQ, logsapiAddr, l)
	}()
	t.Cleanup(func() {
		cancel()
		wg.Wait()
	})

	lambdaServer := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		switch r.RequestURI {
		// Extension registration request
		case "/2020-01-01/extension/register":
			w.Header().Set("Lambda-Extension-Identifier", "b03a29ec-ee63-44cd-8e53-3987a8e8aa8e")
			if err := json.NewEncoder(w).Encode(extension.RegisterResponse{
				FunctionName:    "UnitTestingMockLambda",
				FunctionVersion: "$LATEST",
				Handler:         "main_test.mock_lambda",
			}); err != nil {
				l.Fatalf("Could not encode registration response : %v", err)
				return
			}
		case "/2020-01-01/extension/event/next":
			lambdaServerInternals.WaitGroup.Wait()
			currID := uuid.New().String()
			select {
			case nextEvent := <-eventsChannel:
				sendNextEventInfo(w, currID, nextEvent.Timeout, nextEvent.Type == Shutdown, l)
				wg.Add(1)
				go processMockEvent(mockLogEventQ, currID, nextEvent,
					os.Getenv("ELASTIC_APM_DATA_RECEIVER_SERVER_PORT"), &lambdaServerInternals, l,
					&wg)
			default:
				finalShutDown := MockEvent{
					Type:              Shutdown,
					ExecutionDuration: 0,
					Timeout:           0,
				}
				sendNextEventInfo(w, currID, finalShutDown.Timeout, true, l)
				wg.Add(1)
				go processMockEvent(mockLogEventQ, currID, finalShutDown,
					os.Getenv("ELASTIC_APM_DATA_RECEIVER_SERVER_PORT"), &lambdaServerInternals, l,
					&wg)
			}
		// Logs API subscription request
		case "/2020-08-15/logs":
			w.WriteHeader(http.StatusOK)
		}
	}))

	slicedLambdaURL := strings.Split(lambdaServer.URL, "//")
	strippedLambdaURL := slicedLambdaURL[1]
	t.Setenv("AWS_LAMBDA_RUNTIME_API", strippedLambdaURL)

	// Find unused port for the extension to listen to
	extensionPort, err := e2eTesting.GetFreePort()
	if err != nil {
		l.Errorf("Could not find free port for the extension to listen on : %v", err)
		extensionPort = 8200
	}
	t.Setenv("ELASTIC_APM_DATA_RECEIVER_SERVER_PORT", strconv.Itoa(extensionPort))

	t.Cleanup(func() { lambdaServer.Close() })
	return &lambdaServerInternals
}

func newTestStructs(_ *testing.T) chan MockEvent {
	http.DefaultServeMux = new(http.ServeMux)
	eventsChannel := make(chan MockEvent, 100)
	return eventsChannel
}

func processMockEvent(q chan<- logsapi.LogEvent, currID string, event MockEvent, extensionPort string, internals *MockServerInternals, l *zap.SugaredLogger, wg *sync.WaitGroup) {
	defer wg.Done()
	queueLogEvent(q, currID, logsapi.PlatformStart, l)
	client := http.Client{}

	// Use a custom transport with a low timeout
	tr := http.DefaultTransport.(*http.Transport)
	tr.ResponseHeaderTimeout = 200 * time.Millisecond
	client.Transport = tr

	sendRuntimeDone := true
	sendMetrics := true

	// Used in LateFlush events to make sure that
	// the request is sent after the RuntimeDone.
	ch := make(chan struct{})
	defer close(ch)

	// float values were silently ignored (casted to int)
	// Multiply before casting to support more values.
	delay := time.Duration(event.ExecutionDuration * float64(time.Second))
	buf := bytes.NewBufferString(`{"metadata":{"service":{"name":"1234_service-12a3","version":"5.1.3","environment":"staging","agent":{"name":"elastic-node","version":"3.14.0"},"framework":{"name":"Express","version":"1.2.3"},"language":{"name":"ecmascript","version":"8"},"runtime":{"name":"node","version":"8.0.0"},"node":{"configured_name":"node-123"}},"user":{"username":"bar","id":"123user","email":"bar@user.com"},"labels":{"tag0":null,"tag1":"one","tag2":2},"process":{"pid":1234,"ppid":6789,"title":"node","argv":["node","server.js"]},"system":{"architecture":"x64","hostname":"prod1.example.com","platform":"darwin","container":{"id":"container-id"},"kubernetes":{"namespace":"namespace1","node":{"name":"node-name"},"pod":{"name":"pod-name","uid":"pod-uid"}}},"cloud":{"provider":"cloud_provider","region":"cloud_region","availability_zone":"cloud_availability_zone","instance":{"id":"instance_id","name":"instance_name"},"machine":{"type":"machine_type"},"account":{"id":"account_id","name":"account_name"},"project":{"id":"project_id","name":"project_name"},"service":{"name":"lambda"}}}}`)
	buf.WriteByte('\n')
	buf.WriteString(string(event.APMServerBehavior))

	switch event.Type {
	case InvokeHang:
		time.Sleep(time.Duration(event.Timeout * float64(time.Second)))
	case InvokeStandard:
		time.Sleep(delay)
		req, err := http.NewRequest(http.MethodPost,
			fmt.Sprintf("http://localhost:%s/intake/v2/events", extensionPort), buf)
		if err != nil {
			l.Error(err.Error())
		}
		res, err := client.Do(req)
		if err != nil {
			l.Error(err.Error())
		}
		res.Body.Close()
		l.Debugf("Response seen by the agent : %d", res.StatusCode)
	case InvokeStandardFlush:
		time.Sleep(delay)
		reqData, _ := http.NewRequest(http.MethodPost,
			fmt.Sprintf("http://localhost:%s/intake/v2/events?flushed=true", extensionPort), buf)
		res, err := client.Do(reqData)
		if err != nil {
			l.Error(err.Error())
		}
		res.Body.Close()
	case InvokeLateFlush:
		time.Sleep(delay)
		reqData, _ := http.NewRequest(http.MethodPost,
			fmt.Sprintf("http://localhost:%s/intake/v2/events?flushed=true", extensionPort), buf)
		internals.WaitGroup.Add(1)
		go func() {
			<-ch
			res, err := client.Do(reqData)
			if err != nil {
				l.Error(err.Error())
			}
			res.Body.Close()
			internals.WaitGroup.Done()
		}()
		// For this specific scenario, we do not want to see metrics in the APM Server logs (in order to easily check if the logs contain to "TimelyResponse" back to back).
		sendMetrics = false
	case InvokeWaitgroupsRace:
		time.Sleep(delay)
		// we can't share a bytes.Buffer with two http requests
		// create two bytes.Reader to avoid a race condition
		body := buf.Bytes()
		reqData0, _ := http.NewRequest(http.MethodPost,
			fmt.Sprintf("http://localhost:%s/intake/v2/events", extensionPort),
			bytes.NewReader(body))
		reqData1, _ := http.NewRequest(http.MethodPost,
			fmt.Sprintf("http://localhost:%s/intake/v2/events", extensionPort),
			bytes.NewReader(body))
		res, err := client.Do(reqData0)
		if err != nil {
			l.Error(err.Error())
		}
		res.Body.Close()
		res, err = client.Do(reqData1)
		if err != nil {
			l.Error(err.Error())
		}
		res.Body.Close()
		time.Sleep(650 * time.Microsecond)
	case InvokeMultipleTransactionsOverload:
		// we can't share a bytes.Buffer with two http requests
		// create two bytes.Reader to avoid a race condition
		body := buf.Bytes()
		wg := sync.WaitGroup{}
		for i := 0; i < 10; i++ {
			wg.Add(1)
			go func() {
				time.Sleep(delay)
				reqData, _ := http.NewRequest(http.MethodPost,
					fmt.Sprintf("http://localhost:%s/intake/v2/events", extensionPort),
					bytes.NewReader(body))
				res, err := client.Do(reqData)
				if err != nil {
					l.Error(err.Error())
				}
				res.Body.Close()
				wg.Done()
			}()
		}
		wg.Wait()
	case InvokeStandardInfo:
		time.Sleep(delay)
		req, _ := http.NewRequest(http.MethodPost,
			fmt.Sprintf("http://localhost:%s/", extensionPort),
			bytes.NewBuffer([]byte(event.APMServerBehavior)))
		res, err := client.Do(req)
		if err != nil {
			l.Errorf("No response following info request : %v", err)
			break
		}
		var rawBytes []byte
		rawBytes, _ = io.ReadAll(res.Body)
		res.Body.Close()
		internals.Data += string(rawBytes)
		l.Debugf("Response seen by the agent : %d", res.StatusCode)
	case Shutdown:
	}
	if sendRuntimeDone {
		queueLogEvent(q, currID, logsapi.PlatformRuntimeDone, l)
	}
	if sendMetrics {
		queueLogEvent(q, currID, logsapi.PlatformReport, l)
	}
}

func sendNextEventInfo(w http.ResponseWriter, id string, timeoutSec float64, shutdown bool, l *zap.SugaredLogger) {
	nextEventInfo := extension.NextEventResponse{
		EventType:          "INVOKE",
		DeadlineMs:         time.Now().UnixNano()/int64(time.Millisecond) + int64(timeoutSec*1000),
		RequestID:          id,
		InvokedFunctionArn: "arn:aws:lambda:eu-central-1:627286350134:function:main_unit_test",
		Tracing:            extension.Tracing{},
	}
	if shutdown {
		nextEventInfo.EventType = "SHUTDOWN"
	}

	if err := json.NewEncoder(w).Encode(nextEventInfo); err != nil {
		l.Errorf("Could not encode event : %v", err)
	}
}

func queueLogEvent(q chan<- logsapi.LogEvent, requestID string, logEventType logsapi.LogEventType, l *zap.SugaredLogger) {
	record := logsapi.LogEventRecord{
		RequestID: requestID,
	}
	if logEventType == logsapi.PlatformReport {
		record.Metrics = logsapi.PlatformMetrics{
			BilledDurationMs: 60,
			DurationMs:       59.9,
			MemorySizeMB:     128,
			MaxMemoryUsedMB:  60,
			InitDurationMs:   500,
		}
	}

	logEvent := logsapi.LogEvent{
		Time:   time.Now(),
		Type:   logEventType,
		Record: record,
	}

	// Convert record to JSON (string)
	bufRecord := new(bytes.Buffer)
	if err := json.NewEncoder(bufRecord).Encode(record); err != nil {
		l.Errorf("Could not encode record : %v", err)
	}
	logEvent.StringRecord = bufRecord.String()
	q <- logEvent
}

func startLogSender(ctx context.Context, q <-chan logsapi.LogEvent, logsapiAddr string, l *zap.SugaredLogger) {
	client := http.Client{
		Timeout: 10 * time.Millisecond,
	}
	doSend := func(events []logsapi.LogEvent) error {
		var buf bytes.Buffer
		if err := json.NewEncoder(&buf).Encode(events); err != nil { //nolint:musttag
			return err
		}

		req, err := http.NewRequest(http.MethodPost, "http://"+logsapiAddr, &buf)
		if err != nil {
			return err
		}

		resp, err := client.Do(req)
		if err != nil {
			return err
		}
		defer resp.Body.Close()
		if resp.StatusCode/100 != 2 { //nolint:usestdlibvars
			return fmt.Errorf("received a non 2xx status code: %d", resp.StatusCode)
		}
		return nil
	}

	var batch []logsapi.LogEvent
	flushInterval := time.NewTicker(100 * time.Millisecond)
	defer flushInterval.Stop()
	for {
		select {
		case <-flushInterval.C:
			var trySend bool
			for !trySend {
				// TODO: @lahsivjar mock dropping of logs, batch age and batch size
				// TODO: @lahsivjar is it possible for one batch to have platform.runtimeDone
				// event in middle of the batch?
				select {
				case e := <-q:
					batch = append(batch, e)
				default:
					trySend = true
					if len(batch) > 0 {
						if err := doSend(batch); err != nil {
							l.Warnf("mock lambda API failed to send logs to the extension: %v", err)
						} else {
							batch = batch[:0]
						}
					}
				}
			}
		case <-ctx.Done():
			return
		}
	}
}

func eventQueueGenerator(inputQueue []MockEvent, eventsChannel chan MockEvent) {
	for _, event := range inputQueue {
		eventsChannel <- event
	}
}

// TestStandardEventsChain checks a nominal sequence of events (fast APM server, only one standard event)
func TestStandardEventsChain(t *testing.T) {
	l, err := logger.New(logger.WithLevel(zapcore.DebugLevel))
	require.NoError(t, err)

	eventsChannel := newTestStructs(t)
	apmServerInternals, _ := newMockApmServer(t, l)
	logsapiAddr := randomAddr()
	newMockLambdaServer(t, logsapiAddr, eventsChannel, l)

	eventsChain := []MockEvent{
		{Type: InvokeStandard, APMServerBehavior: TimelyResponse, ExecutionDuration: 1, Timeout: 5},
	}
	eventQueueGenerator(eventsChain, eventsChannel)
	select {
	case <-runApp(t, logsapiAddr):
		assert.Contains(t, apmServerInternals.Data, TimelyResponse)
	case <-time.After(timeout):
		t.Fatalf("timed out waiting for app to finish")
	}
}

// TestStandardEventsChainWithoutLogs checks a nominal sequence of events (fast APM server, only one standard event)
// with logs collection disabled
func TestStandardEventsChainWithoutLogs(t *testing.T) {
	l, err := logger.New(logger.WithLevel(zapcore.DebugLevel))
	require.NoError(t, err)

	eventsChannel := newTestStructs(t)
	apmServerInternals, _ := newMockApmServer(t, l)
	logsapiAddr := randomAddr()
	newMockLambdaServer(t, logsapiAddr, eventsChannel, l)

	eventsChain := []MockEvent{
		{Type: InvokeStandard, APMServerBehavior: TimelyResponse, ExecutionDuration: 1, Timeout: 5},
	}
	eventQueueGenerator(eventsChain, eventsChannel)
	select {
	case <-runAppFull(t, logsapiAddr, true):
		assert.Contains(t, apmServerInternals.Data, TimelyResponse)
	case <-time.After(timeout):
		t.Fatalf("timed out waiting for app to finish")
	}
}

// TestFlush checks if the flushed param does not cause a panic or an unexpected behavior
func TestFlush(t *testing.T) {
	l, err := logger.New(logger.WithLevel(zapcore.DebugLevel))
	require.NoError(t, err)

	eventsChannel := newTestStructs(t)
	apmServerInternals, _ := newMockApmServer(t, l)
	logsapiAddr := randomAddr()
	newMockLambdaServer(t, logsapiAddr, eventsChannel, l)

	eventsChain := []MockEvent{
		{Type: InvokeStandardFlush, APMServerBehavior: TimelyResponse, ExecutionDuration: 1, Timeout: 5},
	}
	eventQueueGenerator(eventsChain, eventsChannel)
	select {
	case <-runApp(t, logsapiAddr):
		assert.Contains(t, apmServerInternals.Data, TimelyResponse)
	case <-time.After(timeout):
		t.Fatalf("timed out waiting for app to finish")
	}
}

// TestLateFlush checks if there is no race condition between RuntimeDone and AgentDone
// The test is built so that the AgentDone signal is received after RuntimeDone, which causes the next event to be interrupted.
func TestLateFlush(t *testing.T) {
	l, err := logger.New(logger.WithLevel(zapcore.DebugLevel))
	require.NoError(t, err)

	eventsChannel := newTestStructs(t)
	apmServerInternals, _ := newMockApmServer(t, l)
	logsapiAddr := randomAddr()
	newMockLambdaServer(t, logsapiAddr, eventsChannel, l)

	eventsChain := []MockEvent{
		{Type: InvokeLateFlush, APMServerBehavior: TimelyResponse, ExecutionDuration: 0, Timeout: 5},
		{Type: InvokeStandard, APMServerBehavior: TimelyResponse, ExecutionDuration: 0, Timeout: 5},
	}
	eventQueueGenerator(eventsChain, eventsChannel)
	select {
	case <-runApp(t, logsapiAddr):
		assert.Regexp(
			t,
			regexp.MustCompile(fmt.Sprintf(".*\n%s.*\n%s", TimelyResponse,
				TimelyResponse)), // metadata followed by TimelyResponsex2
			apmServerInternals.Data,
		)
	case <-time.After(timeout):
		t.Fatalf("timed out waiting for app to finish")
	}
}

// TestWaitGroup checks if there is no race condition between the main waitgroups (issue #128)
func TestWaitGroup(t *testing.T) {
	l, err := logger.New(logger.WithLevel(zapcore.DebugLevel))
	require.NoError(t, err)

	eventsChannel := newTestStructs(t)
	apmServerInternals, _ := newMockApmServer(t, l)
	logsapiAddr := randomAddr()
	newMockLambdaServer(t, logsapiAddr, eventsChannel, l)

	eventsChain := []MockEvent{
		{Type: InvokeWaitgroupsRace, APMServerBehavior: TimelyResponse, ExecutionDuration: 1, Timeout: 500},
	}
	eventQueueGenerator(eventsChain, eventsChannel)
	select {
	case <-runApp(t, logsapiAddr):
		assert.Contains(t, apmServerInternals.Data, TimelyResponse)
	case <-time.After(timeout):
		t.Fatalf("timed out waiting for app to finish")
	}
}

// TestAPMServerDown tests that main does not panic nor runs indefinitely when the APM server is inactive.
func TestAPMServerDown(t *testing.T) {
	l, err := logger.New(logger.WithLevel(zapcore.DebugLevel))
	require.NoError(t, err)

	eventsChannel := newTestStructs(t)
	apmServerInternals, apmServer := newMockApmServer(t, l)
	logsapiAddr := randomAddr()
	newMockLambdaServer(t, logsapiAddr, eventsChannel, l)

	apmServer.Close()
	eventsChain := []MockEvent{
		{Type: InvokeStandard, APMServerBehavior: TimelyResponse, ExecutionDuration: 1, Timeout: 5},
	}
	eventQueueGenerator(eventsChain, eventsChannel)
	select {
	case <-runApp(t, logsapiAddr):
		assert.NotContains(t, apmServerInternals.Data, TimelyResponse)
	case <-time.After(timeout):
		t.Fatalf("timed out waiting for app to finish")
	}
}

// TestAPMServerHangs tests that main does not panic nor runs indefinitely when the APM server does not respond.
func TestAPMServerHangs(t *testing.T) {
	l, err := logger.New(logger.WithLevel(zapcore.DebugLevel))
	require.NoError(t, err)

	eventsChannel := newTestStructs(t)
	apmServerInternals, _ := newMockApmServer(t, l)
	logsapiAddr := randomAddr()
	newMockLambdaServer(t, logsapiAddr, eventsChannel, l)

	eventsChain := []MockEvent{
		{Type: InvokeStandard, APMServerBehavior: Hangs, ExecutionDuration: 1, Timeout: 500},
	}
	eventQueueGenerator(eventsChain, eventsChannel)
	select {
	case <-runApp(t, logsapiAddr):
		assert.NotContains(t, apmServerInternals.Data, Hangs)
		apmServerInternals.UnlockSignalChannel <- struct{}{}
	case <-time.After(timeout):
		t.Fatalf("timed out waiting for app to finish")
	}
}

// TestAPMServerRecovery tests a scenario where the APM server recovers after hanging.
// The default forwarder timeout is 3 seconds, so we wait 5 seconds until we unlock that hanging state.
// Hence, the APM server is waked up just in time to process the TimelyResponse data frame.
func TestAPMServerRecovery(t *testing.T) {
	l, err := logger.New(logger.WithLevel(zapcore.DebugLevel))
	require.NoError(t, err)

	eventsChannel := newTestStructs(t)
	apmServerInternals, _ := newMockApmServer(t, l)
	logsapiAddr := randomAddr()
	newMockLambdaServer(t, logsapiAddr, eventsChannel, l)

	t.Setenv("ELASTIC_APM_DATA_FORWARDER_TIMEOUT", "1s")

	eventsChain := []MockEvent{
		{Type: InvokeStandard, APMServerBehavior: Hangs, ExecutionDuration: 1, Timeout: 5},
		{Type: InvokeStandard, APMServerBehavior: TimelyResponse, ExecutionDuration: 1, Timeout: 5},
	}
	eventQueueGenerator(eventsChain, eventsChannel)
	var wg sync.WaitGroup
	wg.Add(1)
	go func() {
		defer wg.Done()
		time.Sleep(2500 * time.Millisecond) // Cannot multiply time.Second by a float
		apmServerInternals.UnlockSignalChannel <- struct{}{}
	}()
	select {
	case <-runApp(t, logsapiAddr):
		// Make sure mock APM Server processes the Hangs request
		wg.Wait()
		time.Sleep(10 * time.Millisecond)
		assert.Contains(t, apmServerInternals.Data, Hangs)
		assert.Contains(t, apmServerInternals.Data, TimelyResponse)
	case <-time.After(10 * time.Second):
		t.Fatalf("timed out waiting for app to finish")
	}
}

// TestGracePeriodHangs verifies that the WaitforGracePeriod goroutine ends when main() ends.
// This can be checked by asserting that apmTransportStatus is pending after the execution of main.
func TestGracePeriodHangs(t *testing.T) {
	l, err := logger.New(logger.WithLevel(zapcore.DebugLevel))
	require.NoError(t, err)

	eventsChannel := newTestStructs(t)
	apmServerInternals, _ := newMockApmServer(t, l)
	logsapiAddr := randomAddr()
	newMockLambdaServer(t, logsapiAddr, eventsChannel, l)

	eventsChain := []MockEvent{
		{Type: InvokeStandard, APMServerBehavior: Hangs, ExecutionDuration: 1, Timeout: 500},
	}
	eventQueueGenerator(eventsChain, eventsChannel)
	select {
	case <-runApp(t, logsapiAddr):
		time.Sleep(100 * time.Millisecond)
		apmServerInternals.UnlockSignalChannel <- struct{}{}
	case <-time.After(timeout):
		t.Fatalf("timed out waiting for app to finish")
	}
}

// TestAPMServerCrashesDuringExecution tests that main does not panic nor runs indefinitely when the APM server crashes
// during execution.
func TestAPMServerCrashesDuringExecution(t *testing.T) {
	l, err := logger.New(logger.WithLevel(zapcore.DebugLevel))
	require.NoError(t, err)

	eventsChannel := newTestStructs(t)
	apmServerInternals, _ := newMockApmServer(t, l)
	logsapiAddr := randomAddr()
	newMockLambdaServer(t, logsapiAddr, eventsChannel, l)

	eventsChain := []MockEvent{
		{Type: InvokeStandard, APMServerBehavior: Crashes, ExecutionDuration: 1, Timeout: 5},
	}
	eventQueueGenerator(eventsChain, eventsChannel)
	select {
	case <-runApp(t, logsapiAddr):
		assert.NotContains(t, apmServerInternals.Data, Crashes)
	case <-time.After(10 * time.Second):
		t.Fatalf("timed out waiting for app to finish")
	}
}

// TestFullChannel checks that an overload of APM data chunks is handled correctly, events dropped beyond the 100th one
// if no space left in channel, no panic, no infinite hanging.
func TestFullChannel(t *testing.T) {
	l, err := logger.New(logger.WithLevel(zapcore.DebugLevel))
	require.NoError(t, err)

	eventsChannel := newTestStructs(t)
	apmServerInternals, _ := newMockApmServer(t, l)
	logsapiAddr := randomAddr()
	newMockLambdaServer(t, logsapiAddr, eventsChannel, l)

	// Use a smaller buffer size to make it easier to reproduce
	t.Setenv("ELASTIC_APM_LAMBDA_AGENT_DATA_BUFFER_SIZE", "1")

	eventsChain := []MockEvent{
		{Type: InvokeMultipleTransactionsOverload, APMServerBehavior: TimelyResponse, ExecutionDuration: 0.1, Timeout: 5},
	}
	eventQueueGenerator(eventsChain, eventsChannel)
	select {
	case <-runApp(t, logsapiAddr):
		assert.Contains(t, apmServerInternals.Data, TimelyResponse)
	case <-time.After(timeout):
		t.Fatalf("timed out waiting for app to finish")
	}
}

// TestFullChannelSlowAPMServer tests what happens when the APM Data channel is full and the APM server is slow
// (send strategy : background)
func TestFullChannelSlowAPMServer(t *testing.T) {
	l, err := logger.New(logger.WithLevel(zapcore.DebugLevel))
	require.NoError(t, err)

	eventsChannel := newTestStructs(t)
	newMockApmServer(t, l)
	logsapiAddr := randomAddr()
	newMockLambdaServer(t, logsapiAddr, eventsChannel, l)

	t.Setenv("ELASTIC_APM_SEND_STRATEGY", "background")
	// Use a smaller buffer size to make it easier to reproduce
	t.Setenv("ELASTIC_APM_LAMBDA_AGENT_DATA_BUFFER_SIZE", "1")

	eventsChain := []MockEvent{
		{Type: InvokeMultipleTransactionsOverload, APMServerBehavior: SlowResponse, ExecutionDuration: 0.01, Timeout: 5},
	}
	eventQueueGenerator(eventsChain, eventsChannel)
	select {
	case <-runApp(t, logsapiAddr):
		// The test should not hang
	case <-time.After(timeout):
		t.Fatalf("timed out waiting for app to finish")
	}
}

// TestInfoRequest checks if the extension is able to retrieve APM server info (/ endpoint) (fast APM server, only one standard event)
func TestInfoRequest(t *testing.T) {
	l, err := logger.New(logger.WithLevel(zapcore.DebugLevel))
	require.NoError(t, err)

	eventsChannel := newTestStructs(t)
	newMockApmServer(t, l)
	logsapiAddr := randomAddr()
	lambdaServerInternals := newMockLambdaServer(t, logsapiAddr, eventsChannel, l)

	eventsChain := []MockEvent{
		{Type: InvokeStandardInfo, APMServerBehavior: TimelyResponse, ExecutionDuration: 1, Timeout: 5},
	}
	eventQueueGenerator(eventsChain, eventsChannel)
	select {
	case <-runApp(t, logsapiAddr):
		assert.Contains(t, lambdaServerInternals.Data, "7814d524d3602e70b703539c57568cba6964fc20")
	case <-time.After(timeout):
		t.Fatalf("timed out waiting for app to finish")
	}
}

// TestInfoRequest checks if the extension times out when unable to retrieve APM server info (/ endpoint)
func TestInfoRequestHangs(t *testing.T) {
	l, err := logger.New(logger.WithLevel(zapcore.DebugLevel))
	require.NoError(t, err)

	eventsChannel := newTestStructs(t)
	apmServerInternals, _ := newMockApmServer(t, l)
	logsapiAddr := randomAddr()
	lambdaServerInternals := newMockLambdaServer(t, logsapiAddr, eventsChannel, l)

	eventsChain := []MockEvent{
		{Type: InvokeStandardInfo, APMServerBehavior: Hangs, ExecutionDuration: 1, Timeout: 5},
	}
	eventQueueGenerator(eventsChain, eventsChannel)
	select {
	case <-runApp(t, logsapiAddr):
		time.Sleep(2 * time.Second)
		assert.NotContains(t, lambdaServerInternals.Data,
			"7814d524d3602e70b703539c57568cba6964fc20")
		apmServerInternals.UnlockSignalChannel <- struct{}{}
	case <-time.After(timeout):
		t.Fatalf("timed out waiting for app to finish")
	}
}

// TestMetrics checks if the extension sends metrics corresponding to invocation n during invocation
func TestMetrics(t *testing.T) {
	l, err := logger.New(logger.WithLevel(zapcore.DebugLevel))
	require.NoError(t, err)

	eventsChannel := newTestStructs(t)
	apmServerInternals, _ := newMockApmServer(t, l)
	logsapiAddr := randomAddr()
	newMockLambdaServer(t, logsapiAddr, eventsChannel, l)

	eventsChain := []MockEvent{
		{Type: InvokeStandard, APMServerBehavior: TimelyResponse, ExecutionDuration: 1, Timeout: 5},
		{Type: InvokeStandard, APMServerBehavior: TimelyResponse, ExecutionDuration: 1, Timeout: 5},
	}
	eventQueueGenerator(eventsChain, eventsChannel)

	select {
	case <-runApp(t, logsapiAddr):
		assert.Contains(t, apmServerInternals.Data,
			`{"metadata":{"service":{"name":"1234_service-12a3","version":"5.1.3","environment":"staging","agent":{"name":"elastic-node","version":"3.14.0"},"framework":{"name":"Express","version":"1.2.3"},"language":{"name":"ecmascript","version":"8"},"runtime":{"name":"node","version":"8.0.0"},"node":{"configured_name":"node-123"}},"user":{"username":"bar","id":"123user","email":"bar@user.com"},"labels":{"tag0":null,"tag1":"one","tag2":2},"process":{"pid":1234,"ppid":6789,"title":"node","argv":["node","server.js"]},"system":{"architecture":"x64","hostname":"prod1.example.com","platform":"darwin","container":{"id":"container-id"},"kubernetes":{"namespace":"namespace1","node":{"name":"node-name"},"pod":{"name":"pod-name","uid":"pod-uid"}}},"cloud":{"provider":"cloud_provider","region":"cloud_region","availability_zone":"cloud_availability_zone","instance":{"id":"instance_id","name":"instance_name"},"machine":{"type":"machine_type"},"account":{"id":"account_id","name":"account_name"},"project":{"id":"project_id","name":"project_name"},"service":{"name":"lambda"}}}}`)
		assert.Contains(t, apmServerInternals.Data, `faas.billed_duration":{"value":60`)
		assert.Contains(t, apmServerInternals.Data, `faas.duration":{"value":59.9`)
		assert.Contains(t, apmServerInternals.Data, `faas.coldstart_duration":{"value":500`)
		assert.Contains(t, apmServerInternals.Data, `faas.timeout":{"value":5000}`)
		assert.Contains(t, apmServerInternals.Data, `coldstart":true`)
		assert.Contains(t, apmServerInternals.Data, `execution"`)
		assert.Contains(t, apmServerInternals.Data,
			`id":"arn:aws:lambda:eu-central-1:627286350134:function:main_unit_test"`)
	case <-time.After(timeout):
		t.Fatalf("timed out waiting for app to finish")
	}
}

func runApp(t *testing.T, logsapiAddr string) <-chan struct{} {
	return runAppFull(t, logsapiAddr, false)
}

func runAppFull(t *testing.T, logsapiAddr string, disableLogsAPI bool) <-chan struct{} {
	ctx, cancel := context.WithCancel(context.Background())
	opts := []app.ConfigOption{
		app.WithExtensionName("apm-lambda-extension"),
		app.WithLambdaRuntimeAPI(os.Getenv("AWS_LAMBDA_RUNTIME_API")),
		app.WithLogLevel("debug"),
		app.WithLogsapiAddress(logsapiAddr),
	}
	if disableLogsAPI {
		opts = append(opts, app.WithoutLogsAPI())
	}
	application, err := app.New(ctx, opts...)
	require.NoError(t, err)

	go func() {
		assert.NoError(t, application.Run(ctx))
		cancel()
	}()

	return ctx.Done()
}

func randomAddr() string {
	// we cannot return a port that is already in use or it
	// would return an error when creating the server.
	// The solution is to spawn a test server to get a random
	// port and immediately close it so that we can use the port.
	s := httptest.NewServer(nil)
	addr := s.Listener.Addr().String()
	s.Close()

	return addr
}