TUN-3989: Check in with Updater service in more situations and convey messages to user

CHANGES.md

@@ -16,6 +16,9 @@
 - Nested commands, such as `cloudflared tunnel run`, now consider CLI arguments even if they appear earlier on the
   command. For instance, `cloudflared --config config.yaml tunnel run` will now behave the same as
   `cloudflared tunnel --config config.yaml run`
+- Warnings are now shown in the output logs whenever cloudflared is running without the most recent version and
+  `no-autoupdate` is `true`.
+
 
 ### Bug Fixes
 

cmd/cloudflared/tunnel/cmd.go

@@ -286,16 +286,14 @@ func StartServer(
 	}
 
 	// update needs to be after DNS proxy is up to resolve equinox server address
-	if updater.IsAutoupdateEnabled(c, log) {
+	wg.Add(1)
-		autoupdateFreq := c.Duration("autoupdate-freq")
+	go func() {
-		log.Info().Dur("autoupdateFreq", autoupdateFreq).Msg("Autoupdate frequency is set")
+		defer wg.Done()
-		wg.Add(1)
+		autoupdater := updater.NewAutoUpdater(
-		go func() {
+			c.Bool("no-autoupdate"), c.Duration("autoupdate-freq"), &listeners, log,
-			defer wg.Done()
+		)
-			autoupdater := updater.NewAutoUpdater(c.Duration("autoupdate-freq"), &listeners, log)
+		errC <- autoupdater.Run(ctx)
-			errC <- autoupdater.Run(ctx)
+	}()
-		}()
-	}
 
 	// Serve DNS proxy stand-alone if no hostname or tag or app is going to run
 	if dnsProxyStandAlone(c) {

cmd/cloudflared/tunnel/subcommands.go

@@ -13,6 +13,7 @@ import (
 	"text/tabwriter"
 	"time"
 
+	"github.com/cloudflare/cloudflared/cmd/cloudflared/updater"
 	"github.com/google/uuid"
 	"github.com/mitchellh/go-homedir"
 	"github.com/pkg/errors"
@@ -149,6 +150,9 @@ func createCommand(c *cli.Context) error {
 	}
 	name := c.Args().First()
 
+	warningChecker := updater.StartWarningCheck(c)
+	defer warningChecker.LogWarningIfAny(sc.log)
+
 	_, err = sc.create(name, c.String(CredFileFlag))
 	return errors.Wrap(err, "failed to create tunnel")
 }
@@ -227,6 +231,9 @@ func listCommand(c *cli.Context) error {
 		filter.ByTunnelID(tunnelID)
 	}
 
+	warningChecker := updater.StartWarningCheck(c)
+	defer warningChecker.LogWarningIfAny(sc.log)
+
 	tunnels, err := sc.list(filter)
 	if err != nil {
 		return err
@@ -271,6 +278,7 @@ func listCommand(c *cli.Context) error {
 	} else {
 		fmt.Println("You have no tunnels, use 'cloudflared tunnel create' to define a new tunnel")
 	}
+
 	return nil
 }
 
@@ -349,6 +357,9 @@ func deleteCommand(c *cli.Context) error {
 		return cliutil.UsageError(`"cloudflared tunnel delete" requires at least 1 argument, the ID or name of the tunnel to delete.`)
 	}
 
+	warningChecker := updater.StartWarningCheck(c)
+	defer warningChecker.LogWarningIfAny(sc.log)
+
 	tunnelIDs, err := sc.findIDs(c.Args().Slice())
 	if err != nil {
 		return err

cmd/cloudflared/tunnel/teamnet_subcommands.go

@@ -7,6 +7,7 @@ import (
 	"text/tabwriter"
 
 	"github.com/cloudflare/cloudflared/cmd/cloudflared/cliutil"
+	"github.com/cloudflare/cloudflared/cmd/cloudflared/updater"
 	"github.com/cloudflare/cloudflared/teamnet"
 	"github.com/pkg/errors"
 
@@ -81,6 +82,9 @@ func showRoutesCommand(c *cli.Context) error {
 		return errors.Wrap(err, "invalid config for routing filters")
 	}
 
+	warningChecker := updater.StartWarningCheck(c)
+	defer warningChecker.LogWarningIfAny(sc.log)
+
 	routes, err := sc.listRoutes(filter)
 	if err != nil {
 		return err
@@ -95,6 +99,7 @@ func showRoutesCommand(c *cli.Context) error {
 	} else {
 		fmt.Println("You have no routes, use 'cloudflared tunnel route ip add' to add a route")
 	}
+
 	return nil
 }
 

cmd/cloudflared/updater/check.go

@@ -0,0 +1,49 @@
+package updater
+
+import (
+	"github.com/rs/zerolog"
+	"github.com/urfave/cli/v2"
+)
+
+type VersionWarningChecker struct {
+	warningChan chan string
+}
+
+func StartWarningCheck(c *cli.Context) VersionWarningChecker {
+	checker := VersionWarningChecker{
+		warningChan: make(chan string),
+	}
+
+	go func() {
+		options := updateOptions{
+			updateDisabled:  true,
+			isBeta:          c.Bool("beta"),
+			isStaging:       c.Bool("staging"),
+			isForced:        false,
+			intendedVersion: "",
+		}
+		checkResult, err := CheckForUpdate(options)
+		if err == nil {
+			checker.warningChan <- checkResult.UserMessage()
+		}
+		close(checker.warningChan)
+	}()
+
+	return checker
+}
+
+func (checker VersionWarningChecker) getWarning() string {
+	select {
+	case message := <-checker.warningChan:
+		return message
+	default:
+		// No feedback on time, we don't wait for it, since this is best-effort.
+		return ""
+	}
+}
+
+func (checker VersionWarningChecker) LogWarningIfAny(log *zerolog.Logger) {
+	if warning := checker.getWarning(); warning != "" {
+		log.Warn().Msg(warning)
+	}
+}

cmd/cloudflared/updater/service.go

@@ -1,14 +1,15 @@
 package updater
 
-// Version is the functions needed to perform an update
+// CheckResult is the behaviour resulting from checking in with the Update Service
-type Version interface {
+type CheckResult interface {
 	Apply() error
-	String() string
+	Version() string
+	UserMessage() string
 }
 
 // Service is the functions to get check for new updates
 type Service interface {
-	Check() (Version, error)
+	Check() (CheckResult, error)
 }
 
 const (
@@ -23,4 +24,7 @@ const (
 
 	// VersionKeyName is the url parameter key to send to the checkin API to specific what version to upgrade or downgrade to
 	VersionKeyName = "version"
+
+	// ClientVersionName is the url parameter key to send the version that this cloudflared is currently running with
+	ClientVersionName = "clientVersion"
 )

cmd/cloudflared/updater/update.go

@@ -3,18 +3,17 @@ package updater
 import (
 	"context"
 	"fmt"
-	"github.com/rs/zerolog"
 	"os"
 	"path/filepath"
 	"runtime"
 	"time"
 
-	"github.com/urfave/cli/v2"
-	"golang.org/x/crypto/ssh/terminal"
-
 	"github.com/cloudflare/cloudflared/cmd/cloudflared/config"
 	"github.com/cloudflare/cloudflared/logger"
 	"github.com/facebookgo/grace/gracenet"
+	"github.com/rs/zerolog"
+	"github.com/urfave/cli/v2"
+	"golang.org/x/crypto/ssh/terminal"
 )
 
 const (
@@ -61,16 +60,18 @@ func (e *statusErr) ExitCode() int {
 }
 
 type updateOptions struct {
-	isBeta    bool
+	updateDisabled  bool
-	isStaging bool
+	isBeta          bool
-	isForced  bool
+	isStaging       bool
-	version   string
+	isForced        bool
+	intendedVersion string
 }
 
 type UpdateOutcome struct {
-	Updated bool
+	Updated     bool
-	Version string
+	Version     string
-	Error   error
+	UserMessage string
+	Error       error
 }
 
 func (uo *UpdateOutcome) noUpdate() bool {
@@ -81,10 +82,10 @@ func Init(v string) {
 	version = v
 }
 
-func checkForUpdateAndApply(options updateOptions) UpdateOutcome {
+func CheckForUpdate(options updateOptions) (CheckResult, error) {
 	cfdPath, err := os.Executable()
 	if err != nil {
-		return UpdateOutcome{Error: err}
+		return nil, err
 	}
 
 	url := UpdateURL
@@ -93,24 +94,22 @@ func checkForUpdateAndApply(options updateOptions) UpdateOutcome {
 	}
 
 	s := NewWorkersService(version, url, cfdPath, Options{IsBeta: options.isBeta,
-		IsForced: options.isForced, RequestedVersion: options.version})
+		IsForced: options.isForced, RequestedVersion: options.intendedVersion})
 
-	v, err := s.Check()
+	return s.Check()
+}
+
+func applyUpdate(options updateOptions, update CheckResult) UpdateOutcome {
+	if update.Version() == "" || options.updateDisabled {
+		return UpdateOutcome{UserMessage: update.UserMessage()}
+	}
+
+	err := update.Apply()
 	if err != nil {
 		return UpdateOutcome{Error: err}
 	}
 
-	//already on the latest version
+	return UpdateOutcome{Updated: true, Version: update.Version(), UserMessage: update.UserMessage()}
-	if v == nil {
-		return UpdateOutcome{}
-	}
-
-	err = v.Apply()
-	if err != nil {
-		return UpdateOutcome{Error: err}
-	}
-
-	return UpdateOutcome{Updated: true, Version: v.String()}
 }
 
 // Update is the handler for the update command from the command line
@@ -137,7 +136,13 @@ func Update(c *cli.Context) error {
 		log.Info().Msg("cloudflared is set to upgrade to the latest publish version regardless of the current version")
 	}
 
-	updateOutcome := loggedUpdate(log, updateOptions{isBeta: isBeta, isStaging: isStaging, isForced: isForced, version: c.String("version")})
+	updateOutcome := loggedUpdate(log, updateOptions{
+		updateDisabled:  false,
+		isBeta:          isBeta,
+		isStaging:       isStaging,
+		isForced:        isForced,
+		intendedVersion: c.String("version"),
+	})
 	if updateOutcome.Error != nil {
 		return &statusErr{updateOutcome.Error}
 	}
@@ -152,12 +157,18 @@ func Update(c *cli.Context) error {
 
 // Checks for an update and applies it if one is available
 func loggedUpdate(log *zerolog.Logger, options updateOptions) UpdateOutcome {
-	updateOutcome := checkForUpdateAndApply(options)
+	checkResult, err := CheckForUpdate(options)
+	if err != nil {
+		log.Err(err).Msg("update check failed")
+		return UpdateOutcome{Error: err}
+	}
+
+	updateOutcome := applyUpdate(options, checkResult)
 	if updateOutcome.Updated {
 		log.Info().Str(LogFieldVersion, updateOutcome.Version).Msg("cloudflared has been updated")
 	}
 	if updateOutcome.Error != nil {
-		log.Err(updateOutcome.Error).Msg("update check failed: %s")
+		log.Err(updateOutcome.Error).Msg("update failed to apply")
 	}
 
 	return updateOutcome
@@ -177,44 +188,53 @@ type configurable struct {
 	freq    time.Duration
 }
 
-func NewAutoUpdater(freq time.Duration, listeners *gracenet.Net, log *zerolog.Logger) *AutoUpdater {
+func NewAutoUpdater(updateDisabled bool, freq time.Duration, listeners *gracenet.Net, log *zerolog.Logger) *AutoUpdater {
-	updaterConfigurable := &configurable{
-		enabled: true,
-		freq:    freq,
-	}
-	if freq == 0 {
-		updaterConfigurable.enabled = false
-		updaterConfigurable.freq = DefaultCheckUpdateFreq
-	}
 	return &AutoUpdater{
-		configurable:     updaterConfigurable,
+		configurable:     createUpdateConfig(updateDisabled, freq, log),
 		listeners:        listeners,
 		updateConfigChan: make(chan *configurable),
 		log:              log,
 	}
 }
 
+func createUpdateConfig(updateDisabled bool, freq time.Duration, log *zerolog.Logger) *configurable {
+	if isAutoupdateEnabled(log, updateDisabled, freq) {
+		log.Info().Dur("autoupdateFreq", freq).Msg("Autoupdate frequency is set")
+		return &configurable{
+			enabled: true,
+			freq:    freq,
+		}
+	} else {
+		return &configurable{
+			enabled: false,
+			freq:    DefaultCheckUpdateFreq,
+		}
+	}
+}
+
 func (a *AutoUpdater) Run(ctx context.Context) error {
 	ticker := time.NewTicker(a.configurable.freq)
 	for {
-		if a.configurable.enabled {
+		updateOutcome := loggedUpdate(a.log, updateOptions{updateDisabled: !a.configurable.enabled})
-			updateOutcome := loggedUpdate(a.log, updateOptions{})
+		if updateOutcome.Updated {
-			if updateOutcome.Updated {
+			Init(updateOutcome.Version)
-				if IsSysV() {
+			if IsSysV() {
-					// SysV doesn't have a mechanism to keep service alive, we have to restart the process
+				// SysV doesn't have a mechanism to keep service alive, we have to restart the process
-					a.log.Info().Msg("Restarting service managed by SysV...")
+				a.log.Info().Msg("Restarting service managed by SysV...")
-					pid, err := a.listeners.StartProcess()
+				pid, err := a.listeners.StartProcess()
-					if err != nil {
+				if err != nil {
-						a.log.Err(err).Msg("Unable to restart server automatically")
+					a.log.Err(err).Msg("Unable to restart server automatically")
-						return &statusErr{err: err}
+					return &statusErr{err: err}
-					}
-					// stop old process after autoupdate. Otherwise we create a new process
-					// after each update
-					a.log.Info().Msgf("PID of the new process is %d", pid)
 				}
-				return &statusSuccess{newVersion: updateOutcome.Version}
+				// stop old process after autoupdate. Otherwise we create a new process
+				// after each update
+				a.log.Info().Msgf("PID of the new process is %d", pid)
 			}
+			return &statusSuccess{newVersion: updateOutcome.Version}
+		} else if updateOutcome.UserMessage != "" {
+			a.log.Warn().Msg(updateOutcome.UserMessage)
 		}
+
 		select {
 		case <-ctx.Done():
 			return ctx.Err()
@@ -229,27 +249,18 @@ func (a *AutoUpdater) Run(ctx context.Context) error {
 }
 
 // Update is the method to pass new AutoUpdaterConfigurable to a running AutoUpdater. It is safe to be called concurrently
-func (a *AutoUpdater) Update(newFreq time.Duration) {
+func (a *AutoUpdater) Update(updateDisabled bool, newFreq time.Duration) {
-	newConfigurable := &configurable{
+	a.updateConfigChan <- createUpdateConfig(updateDisabled, newFreq, a.log)
-		enabled: true,
-		freq:    newFreq,
-	}
-	// A ero duration means autoupdate is disabled
-	if newFreq == 0 {
-		newConfigurable.enabled = false
-		newConfigurable.freq = DefaultCheckUpdateFreq
-	}
-	a.updateConfigChan <- newConfigurable
 }
 
-func IsAutoupdateEnabled(c *cli.Context, log *zerolog.Logger) bool {
+func isAutoupdateEnabled(log *zerolog.Logger, updateDisabled bool, updateFreq time.Duration) bool {
-	if !SupportAutoUpdate(log) {
+	if !supportAutoUpdate(log) {
 		return false
 	}
-	return !c.Bool("no-autoupdate") && c.Duration("autoupdate-freq") != 0
+	return !updateDisabled && updateFreq != 0
 }
 
-func SupportAutoUpdate(log *zerolog.Logger) bool {
+func supportAutoUpdate(log *zerolog.Logger) bool {
 	if runtime.GOOS == "windows" {
 		log.Info().Msg(noUpdateOnWindowsMessage)
 		return false

cmd/cloudflared/updater/update_test.go

@@ -2,17 +2,19 @@ package updater
 
 import (
 	"context"
+	"flag"
 	"testing"
 
 	"github.com/facebookgo/grace/gracenet"
 	"github.com/rs/zerolog"
 	"github.com/stretchr/testify/assert"
+	"github.com/urfave/cli/v2"
 )
 
 func TestDisabledAutoUpdater(t *testing.T) {
 	listeners := &gracenet.Net{}
 	log := zerolog.Nop()
-	autoupdater := NewAutoUpdater(0, listeners, &log)
+	autoupdater := NewAutoUpdater(false, 0, listeners, &log)
 	ctx, cancel := context.WithCancel(context.Background())
 	errC := make(chan error)
 	go func() {
@@ -26,3 +28,13 @@ func TestDisabledAutoUpdater(t *testing.T) {
 	// Make sure that autoupdater terminates after canceling the context
 	assert.Equal(t, context.Canceled, <-errC)
 }
+
+func TestCheckInWithUpdater(t *testing.T) {
+	flagSet := flag.NewFlagSet(t.Name(), flag.PanicOnError)
+	cliCtx := cli.NewContext(cli.NewApp(), flagSet, nil)
+
+	warningChecker := StartWarningCheck(cliCtx)
+	warning := warningChecker.getWarning()
+	// Assuming this runs either on a release or development version, then the Worker will never have anything to tell us.
+	assert.Empty(t, warning)
+}

cmd/cloudflared/updater/workers_service.go

@@ -27,6 +27,7 @@ type VersionResponse struct {
 	Version      string `json:"version"`
 	Checksum     string `json:"checksum"`
 	IsCompressed bool   `json:"compressed"`
+	UserMessage  string `json:"userMessage"`
 	Error        string `json:"error"`
 }
 
@@ -50,7 +51,7 @@ func NewWorkersService(currentVersion, url, targetPath string, opts Options) Ser
 }
 
 // Check does a check in with the Workers API to get a new version update
-func (s *WorkersService) Check() (Version, error) {
+func (s *WorkersService) Check() (CheckResult, error) {
 	client := &http.Client{
 		Timeout: clientTimeout,
 	}
@@ -59,6 +60,7 @@ func (s *WorkersService) Check() (Version, error) {
 	q := req.URL.Query()
 	q.Add(OSKeyName, runtime.GOOS)
 	q.Add(ArchitectureKeyName, runtime.GOARCH)
+	q.Add(ClientVersionName, s.currentVersion)
 
 	if s.opts.IsBeta {
 		q.Add(BetaKeyName, "true")
@@ -84,11 +86,12 @@ func (s *WorkersService) Check() (Version, error) {
 		return nil, errors.New(v.Error)
 	}
 
-	if !s.opts.IsForced && !IsNewerVersion(s.currentVersion, v.Version) {
+	var versionToUpdate = ""
-		return nil, nil
+	if s.opts.IsForced || IsNewerVersion(s.currentVersion, v.Version) {
+		versionToUpdate = v.Version
 	}
 
-	return NewWorkersVersion(v.URL, v.Version, v.Checksum, s.targetPath, v.IsCompressed), nil
+	return NewWorkersVersion(v.URL, versionToUpdate, v.Checksum, s.targetPath, v.UserMessage, v.IsCompressed), nil
 }
 
 // IsNewerVersion checks semantic versioning for the latest version

cmd/cloudflared/updater/workers_service_test.go

@@ -32,15 +32,20 @@ func respondWithData(w http.ResponseWriter, b []byte, status int) {
 	w.Write(b)
 }
 
+const mostRecentVersion = "2021.2.5"
+const mostRecentBetaVersion = "2021.3.0"
+const knownBuggyVersion = "2020.12.0"
+const expectedUserMsg = "This message is expected when running a known buggy version"
+
 func updateHandler(w http.ResponseWriter, r *http.Request) {
-	version := "2020.08.05"
+	version := mostRecentVersion
 	host := fmt.Sprintf("http://%s", r.Host)
 	url := host + "/download"
 
 	query := r.URL.Query()
 
 	if query.Get(BetaKeyName) == "true" {
-		version = "2020.08.06"
+		version = mostRecentBetaVersion
 		url = host + "/beta"
 	}
 
@@ -59,7 +64,12 @@ func updateHandler(w http.ResponseWriter, r *http.Request) {
 	fmt.Fprint(h, version)
 	checksum := fmt.Sprintf("%x", h.Sum(nil))
 
-	v := VersionResponse{URL: url, Version: version, Checksum: checksum}
+	var userMessage = ""
+	if query.Get(ClientVersionName) == knownBuggyVersion {
+		userMessage = expectedUserMsg
+	}
+
+	v := VersionResponse{URL: url, Version: version, Checksum: checksum, UserMessage: userMessage}
 	respondWithJSON(w, v, http.StatusOK)
 }
 
@@ -96,7 +106,7 @@ func compressedDownloadHandler(w http.ResponseWriter, r *http.Request) {
 }
 
 func downloadHandler(w http.ResponseWriter, r *http.Request) {
-	version := "2020.08.05"
+	version := mostRecentVersion
 	requestedVersion := r.URL.Query().Get(VersionKeyName)
 	if requestedVersion != "" {
 		version = requestedVersion
@@ -105,7 +115,7 @@ func downloadHandler(w http.ResponseWriter, r *http.Request) {
 }
 
 func betaHandler(w http.ResponseWriter, r *http.Request) {
-	respondWithData(w, []byte("2020.08.06"), http.StatusOK)
+	respondWithData(w, []byte(mostRecentBetaVersion), http.StatusOK)
 }
 
 func failureHandler(w http.ResponseWriter, r *http.Request) {
@@ -124,7 +134,7 @@ func createServer() *httptest.Server {
 }
 
 func createTestFile(t *testing.T, path string) {
-	f, err := os.Create("tmpfile")
+	f, err := os.Create(path)
 	require.NoError(t, err)
 	fmt.Fprint(f, "2020.08.04")
 	f.Close()
@@ -142,13 +152,13 @@ func TestUpdateService(t *testing.T) {
 	s := NewWorkersService("2020.8.2", fmt.Sprintf("%s/updater", ts.URL), testFilePath, Options{})
 	v, err := s.Check()
 	require.NoError(t, err)
-	require.Equal(t, v.String(), "2020.08.05")
+	require.Equal(t, v.Version(), mostRecentVersion)
 
 	require.NoError(t, v.Apply())
 	dat, err := ioutil.ReadFile(testFilePath)
 	require.NoError(t, err)
 
-	require.Equal(t, string(dat), "2020.08.05")
+	require.Equal(t, string(dat), mostRecentVersion)
 }
 
 func TestBetaUpdateService(t *testing.T) {
@@ -162,13 +172,13 @@ func TestBetaUpdateService(t *testing.T) {
 	s := NewWorkersService("2020.8.2", fmt.Sprintf("%s/updater", ts.URL), testFilePath, Options{IsBeta: true})
 	v, err := s.Check()
 	require.NoError(t, err)
-	require.Equal(t, v.String(), "2020.08.06")
+	require.Equal(t, v.Version(), mostRecentBetaVersion)
 
 	require.NoError(t, v.Apply())
 	dat, err := ioutil.ReadFile(testFilePath)
 	require.NoError(t, err)
 
-	require.Equal(t, string(dat), "2020.08.06")
+	require.Equal(t, string(dat), mostRecentBetaVersion)
 }
 
 func TestFailUpdateService(t *testing.T) {
@@ -193,10 +203,11 @@ func TestNoUpdateService(t *testing.T) {
 	createTestFile(t, testFilePath)
 	defer os.Remove(testFilePath)
 
-	s := NewWorkersService("2020.8.5", fmt.Sprintf("%s/updater", ts.URL), testFilePath, Options{})
+	s := NewWorkersService(mostRecentVersion, fmt.Sprintf("%s/updater", ts.URL), testFilePath, Options{})
 	v, err := s.Check()
 	require.NoError(t, err)
-	require.Nil(t, v)
+	require.NotNil(t, v)
+	require.Empty(t, v.Version())
 }
 
 func TestForcedUpdateService(t *testing.T) {
@@ -210,13 +221,13 @@ func TestForcedUpdateService(t *testing.T) {
 	s := NewWorkersService("2020.8.5", fmt.Sprintf("%s/updater", ts.URL), testFilePath, Options{IsForced: true})
 	v, err := s.Check()
 	require.NoError(t, err)
-	require.Equal(t, v.String(), "2020.08.05")
+	require.Equal(t, v.Version(), mostRecentVersion)
 
 	require.NoError(t, v.Apply())
 	dat, err := ioutil.ReadFile(testFilePath)
 	require.NoError(t, err)
 
-	require.Equal(t, string(dat), "2020.08.05")
+	require.Equal(t, string(dat), mostRecentVersion)
 }
 
 func TestUpdateSpecificVersionService(t *testing.T) {
@@ -231,7 +242,7 @@ func TestUpdateSpecificVersionService(t *testing.T) {
 	s := NewWorkersService("2020.8.2", fmt.Sprintf("%s/updater", ts.URL), testFilePath, Options{RequestedVersion: reqVersion})
 	v, err := s.Check()
 	require.NoError(t, err)
-	require.Equal(t, reqVersion, v.String())
+	require.Equal(t, reqVersion, v.Version())
 
 	require.NoError(t, v.Apply())
 	dat, err := ioutil.ReadFile(testFilePath)
@@ -251,7 +262,7 @@ func TestCompressedUpdateService(t *testing.T) {
 	s := NewWorkersService("2020.8.2", fmt.Sprintf("%s/compressed", ts.URL), testFilePath, Options{})
 	v, err := s.Check()
 	require.NoError(t, err)
-	require.Equal(t, "2020.09.02", v.String())
+	require.Equal(t, "2020.09.02", v.Version())
 
 	require.NoError(t, v.Apply())
 	dat, err := ioutil.ReadFile(testFilePath)
@@ -260,6 +271,21 @@ func TestCompressedUpdateService(t *testing.T) {
 	require.Equal(t, "2020.09.02", string(dat))
 }
 
+func TestUpdateWhenRunningKnownBuggyVersion(t *testing.T) {
+	ts := createServer()
+	defer ts.Close()
+
+	testFilePath := "tmpfile"
+	createTestFile(t, testFilePath)
+	defer os.Remove(testFilePath)
+
+	s := NewWorkersService(knownBuggyVersion, fmt.Sprintf("%s/updater", ts.URL), testFilePath, Options{})
+	v, err := s.Check()
+	require.NoError(t, err)
+	require.Equal(t, v.Version(), mostRecentVersion)
+	require.Equal(t, v.UserMessage(), expectedUserMsg)
+}
+
 func TestVersionParsing(t *testing.T) {
 	require.False(t, IsNewerVersion("2020.8.2", "2020.8.2"))
 	require.True(t, IsNewerVersion("2020.8.2", "2020.8.3"))

cmd/cloudflared/updater/workers_update.go

@@ -54,6 +54,7 @@ type WorkersVersion struct {
 	version      string
 	targetPath   string
 	isCompressed bool
+	userMessage  string
 }
 
 // NewWorkersVersion creates a new Version object. This is normally created by a WorkersService JSON checkin response
@@ -61,8 +62,17 @@ type WorkersVersion struct {
 // version is the version of this update
 // checksum is the expected checksum of the downloaded file
 // target path is where the file should be replace. Normally this the running cloudflared's path
-func NewWorkersVersion(url, version, checksum, targetPath string, isCompressed bool) Version {
+// userMessage is a possible message to convey back to the user after having checked in with the Updater Service
-	return &WorkersVersion{downloadURL: url, version: version, checksum: checksum, targetPath: targetPath, isCompressed: isCompressed}
+// isCompressed tells whether the asset to update cloudflared is compressed or not
+func NewWorkersVersion(url, version, checksum, targetPath, userMessage string, isCompressed bool) CheckResult {
+	return &WorkersVersion{
+		downloadURL:  url,
+		version:      version,
+		checksum:     checksum,
+		targetPath:   targetPath,
+		isCompressed: isCompressed,
+		userMessage:  userMessage,
+	}
 }
 
 // Apply does the actual verification and update logic.
@@ -114,10 +124,16 @@ func (v *WorkersVersion) Apply() error {
 }
 
 // String returns the version number of this update/release (e.g. 2020.08.05)
-func (v *WorkersVersion) String() string {
+func (v *WorkersVersion) Version() string {
 	return v.version
 }
 
+// String returns a possible message to convey back to user after having checked in with the Updater Service. E.g.
+// it can warn about the need to update the version currently running.
+func (v *WorkersVersion) UserMessage() string {
+	return v.userMessage
+}
+
 // download the file from the link in the json
 func download(url, filepath string, isCompressed bool) error {
 	client := &http.Client{