TUN-1885: Reconfigure cloudflared on receiving new ClientConfig

cmd/cloudflared/updater/update.go

@@ -1,6 +1,7 @@
 package updater
 
 import (
+	"context"
 	"os"
 	"runtime"
 	"time"
@@ -14,6 +15,7 @@ import (
 )
 
 const (
+	DefaultCheckUpdateFreq   = time.Hour * 24
 	appID                    = "app_idCzgxYerVD"
 	noUpdateInShellMessage   = "cloudflared will not automatically update when run from the shell. To enable auto-updates, run cloudflared as a service: https://developers.cloudflare.com/argo-tunnel/reference/service/"
 	noUpdateOnWindowsMessage = "cloudflared will not automatically update on Windows systems."
@@ -75,30 +77,6 @@ func Update(_ *cli.Context) error {
 	return updateOutcome.Error
 }
 
-func Autoupdate(freq time.Duration, listeners *gracenet.Net, shutdownC chan struct{}) error {
-	tickC := time.Tick(freq)
-	for {
-		updateOutcome := loggedUpdate()
-		if updateOutcome.Updated {
-			os.Args = append(os.Args, "--is-autoupdated=true")
-			pid, err := listeners.StartProcess()
-			if err != nil {
-				logger.WithError(err).Error("Unable to restart server automatically")
-				return err
-			}
-			// stop old process after autoupdate. Otherwise we create a new process
-			// after each update
-			logger.Infof("PID of the new process is %d", pid)
-			return nil
-		}
-		select {
-		case <-tickC:
-		case <-shutdownC:
-			return nil
-		}
-	}
-}
-
 // Checks for an update and applies it if one is available
 func loggedUpdate() UpdateOutcome {
 	updateOutcome := checkForUpdateAndApply()
@@ -112,7 +90,88 @@ func loggedUpdate() UpdateOutcome {
 	return updateOutcome
 }
 
+// AutoUpdater periodically checks for new version of cloudflared.
+type AutoUpdater struct {
+	configurable     *configurable
+	listeners        *gracenet.Net
+	updateConfigChan chan *configurable
+}
+
+// AutoUpdaterConfigurable is the attributes of AutoUpdater that can be reconfigured during runtime
+type configurable struct {
+	enabled bool
+	freq    time.Duration
+}
+
+func NewAutoUpdater(freq time.Duration, listeners *gracenet.Net) *AutoUpdater {
+	updaterConfigurable := &configurable{
+		enabled: true,
+		freq:    freq,
+	}
+	if freq == 0 {
+		updaterConfigurable.enabled = false
+		updaterConfigurable.freq = DefaultCheckUpdateFreq
+	}
+	return &AutoUpdater{
+		configurable:     updaterConfigurable,
+		listeners:        listeners,
+		updateConfigChan: make(chan *configurable),
+	}
+}
+
+func (a *AutoUpdater) Run(ctx context.Context) error {
+	ticker := time.NewTicker(a.configurable.freq)
+	for {
+		if a.configurable.enabled {
+			updateOutcome := loggedUpdate()
+			if updateOutcome.Updated {
+				os.Args = append(os.Args, "--is-autoupdated=true")
+				pid, err := a.listeners.StartProcess()
+				if err != nil {
+					logger.WithError(err).Error("Unable to restart server automatically")
+					return err
+				}
+				// stop old process after autoupdate. Otherwise we create a new process
+				// after each update
+				logger.Infof("PID of the new process is %d", pid)
+				return nil
+			}
+		}
+		select {
+		case <-ctx.Done():
+			return ctx.Err()
+		case newConfigurable := <-a.updateConfigChan:
+			ticker.Stop()
+			a.configurable = newConfigurable
+			ticker = time.NewTicker(a.configurable.freq)
+			// Check if there is new version of cloudflared after receiving new AutoUpdaterConfigurable
+		case <-ticker.C:
+		}
+	}
+}
+
+// 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) {
+	newConfigurable := &configurable{
+		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) bool {
+	if !SupportAutoUpdate() {
+		return false
+	}
+	return !c.Bool("no-autoupdate") && c.Duration("autoupdate-freq") != 0
+}
+
+func SupportAutoUpdate() bool {
 	if runtime.GOOS == "windows" {
 		logger.Info(noUpdateOnWindowsMessage)
 		return false
@@ -122,8 +181,7 @@ func IsAutoupdateEnabled(c *cli.Context) bool {
 		logger.Info(noUpdateInShellMessage)
 		return false
 	}
-
-	return !c.Bool("no-autoupdate") && c.Duration("autoupdate-freq") != 0
+	return true
 }
 
 func isRunningFromTerminal() bool {

cmd/cloudflared/updater/update_test.go

@@ -0,0 +1,26 @@
+package updater
+
+import (
+	"context"
+	"testing"
+
+	"github.com/facebookgo/grace/gracenet"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestDisabledAutoUpdater(t *testing.T) {
+	listeners := &gracenet.Net{}
+	autoupdater := NewAutoUpdater(0, listeners)
+	ctx, cancel := context.WithCancel(context.Background())
+	errC := make(chan error)
+	go func() {
+		errC <- autoupdater.Run(ctx)
+	}()
+
+	assert.False(t, autoupdater.configurable.enabled)
+	assert.Equal(t, DefaultCheckUpdateFreq, autoupdater.configurable.freq)
+
+	cancel()
+	// Make sure that autoupdater terminates after canceling the context
+	assert.Equal(t, context.Canceled, <-errC)
+}