control/controlclient: remove some channels (quit, updateCh)

Updates #cleanup

Change-Id: Ie4820b64f1ad276129e4f81a609fa14e7e04604b
Co-authored-by: Maisem Ali <maisem@tailscale.com>
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

control/controlclient/auto.go

@@ -45,24 +45,24 @@ func (g *LoginGoal) sendLogoutError(err error) {
 
 var _ Client = (*Auto)(nil)
 
-// waitUnpause waits until the client is unpaused then returns. It only
-// returns an error if the client is closed.
-func (c *Auto) waitUnpause(routineLogName string) error {
+// waitUnpause waits until either the client is unpaused or the Auto client is
+// shut down. It reports whether the client should keep running (i.e. it's not
+// closed).
+func (c *Auto) waitUnpause(routineLogName string) (keepRunning bool) {
 	c.mu.Lock()
 	if !c.paused {
-		c.mu.Unlock()
-		return nil
+		defer c.mu.Unlock()
+		return !c.closed
 	}
 	unpaused := c.unpausedChanLocked()
 	c.mu.Unlock()
+
 	c.logf("%s: awaiting unpause", routineLogName)
-	select {
-	case <-unpaused:
+	v := <-unpaused
+	if v {
 		c.logf("%s: unpaused", routineLogName)
-		return nil
-	case <-c.quit:
-		return errors.New("quit")
 	}
+	return v
 }
 
 // updateRoutine is responsible for informing the server of worthy changes to
@@ -76,7 +76,7 @@ func (c *Auto) updateRoutine() {
 	var lastUpdateGenInformed updateGen
 
 	for {
-		if err := c.waitUnpause("updateRoutine"); err != nil {
+		if !c.waitUnpause("updateRoutine") {
 			c.logf("updateRoutine: exiting")
 			return
 		}
@@ -86,19 +86,11 @@ func (c *Auto) updateRoutine() {
 		needUpdate := gen > 0 && gen != lastUpdateGenInformed && c.loggedIn
 		c.mu.Unlock()
 
-		if needUpdate {
-			select {
-			case <-c.quit:
-				c.logf("updateRoutine: exiting")
-				return
-			default:
-			}
-		} else {
+		if !needUpdate {
 			// Nothing to do, wait for a signal.
 			select {
-			case <-c.quit:
-				c.logf("updateRoutine: exiting")
-				return
+			case <-ctx.Done():
+				continue
 			case <-c.updateCh:
 				continue
 			}
@@ -141,7 +133,6 @@ type Auto struct {
 	logf     logger.Logf
 	closed   bool
 	updateCh chan struct{} // readable when we should inform the server of a change
-	newMapCh chan struct{} // readable when we must restart a map request
 	observer Observer      // called to update Client status; always non-nil
 
 	unregisterHealthWatch func()
@@ -155,7 +146,7 @@ type Auto struct {
 	lastUpdateGen updateGen
 
 	paused         bool // whether we should stop making HTTP requests
-	unpauseWaiters []chan struct{}
+	unpauseWaiters []chan bool
 	loggedIn       bool       // true if currently logged in
 	loginGoal      *LoginGoal // non-nil if some login activity is desired
 	synced         bool       // true if our netmap is up-to-date
@@ -165,7 +156,6 @@ type Auto struct {
 	mapCtx     context.Context // context used for netmap and update requests
 	authCancel func()          // cancel authCtx
 	mapCancel  func()          // cancel mapCtx
-	quit       chan struct{}   // when closed, goroutines should all exit
 	authDone   chan struct{}   // when closed, authRoutine is done
 	mapDone    chan struct{}   // when closed, mapRoutine is done
 	updateDone chan struct{}   // when closed, updateRoutine is done
@@ -206,8 +196,6 @@ func NewNoStart(opts Options) (_ *Auto, err error) {
 		clock:      opts.Clock,
 		logf:       opts.Logf,
 		updateCh:   make(chan struct{}, 1),
-		newMapCh:   make(chan struct{}, 1),
-		quit:       make(chan struct{}),
 		authDone:   make(chan struct{}),
 		mapDone:    make(chan struct{}),
 		updateDone: make(chan struct{}),
@@ -241,7 +229,7 @@ func (c *Auto) SetPaused(paused bool) {
 		c.cancelMapCtxLocked()
 	} else {
 		for _, ch := range c.unpauseWaiters {
-			close(ch)
+			ch <- true
 		}
 		c.unpauseWaiters = nil
 	}
@@ -325,16 +313,6 @@ func (c *Auto) restartMap() {
 	c.mu.Unlock()
 
 	c.logf("[v1] restartMap: synced=%v", synced)
-
-	select {
-	case c.newMapCh <- struct{}{}:
-		c.logf("[v1] restartMap: wrote to channel")
-	default:
-		// if channel write failed, then there was already
-		// an outstanding newMapCh request. One is enough,
-		// since it'll always use the latest endpoints.
-		c.logf("[v1] restartMap: channel was full")
-	}
 	c.updateControl()
 }
 
@@ -343,6 +321,10 @@ func (c *Auto) authRoutine() {
 	bo := backoff.NewBackoff("authRoutine", c.logf, 30*time.Second)
 
 	for {
+		if !c.waitUnpause("authRoutine") {
+			c.logf("authRoutine: exiting")
+			return
+		}
 		c.mu.Lock()
 		goal := c.loginGoal
 		ctx := c.authCtx
@@ -353,13 +335,6 @@ func (c *Auto) authRoutine() {
 		}
 		c.mu.Unlock()
 
-		select {
-		case <-c.quit:
-			c.logf("[v1] authRoutine: quit")
-			return
-		default:
-		}
-
 		report := func(err error, msg string) {
 			c.logf("[v1] %s: %v", msg, err)
 			// don't send status updates for context errors,
@@ -476,12 +451,12 @@ func (c *Auto) DirectForTest() *Direct {
 	return c.direct
 }
 
-// unpausedChanLocked returns a new channel that is closed when the
-// current Auto pause is unpaused.
+// unpausedChanLocked returns a new channel that gets sent
+// either a true when unpaused or false on Auto.Shutdown.
 //
 // c.mu must be held
-func (c *Auto) unpausedChanLocked() <-chan struct{} {
-	unpaused := make(chan struct{})
+func (c *Auto) unpausedChanLocked() <-chan bool {
+	unpaused := make(chan bool, 1)
 	c.unpauseWaiters = append(c.unpauseWaiters, unpaused)
 	return unpaused
 }
@@ -523,7 +498,7 @@ func (c *Auto) mapRoutine() {
 	}
 
 	for {
-		if err := c.waitUnpause("mapRoutine"); err != nil {
+		if !c.waitUnpause("mapRoutine") {
 			c.logf("mapRoutine: exiting")
 			return
 		}
@@ -534,13 +509,6 @@ func (c *Auto) mapRoutine() {
 		ctx := c.mapCtx
 		c.mu.Unlock()
 
-		select {
-		case <-c.quit:
-			c.logf("mapRoutine: quit")
-			return
-		default:
-		}
-
 		report := func(err error, msg string) {
 			c.logf("[v1] %s: %v", msg, err)
 			err = fmt.Errorf("%s: %w", msg, err)
@@ -558,36 +526,33 @@ func (c *Auto) mapRoutine() {
 			// c.state is set by authRoutine()
 			c.mu.Unlock()
 
-			select {
-			case <-ctx.Done():
-				c.logf("[v1] mapRoutine: context done.")
-			case <-c.newMapCh:
-				c.logf("[v1] mapRoutine: new map needed while idle.")
-			}
-		} else {
-			health.SetOutOfPollNetMap()
+			<-ctx.Done()
+			c.logf("[v1] mapRoutine: context done.")
+			continue
 
-			err := c.direct.PollNetMap(ctx, mrs)
+		}
+		health.SetOutOfPollNetMap()
 
-			health.SetOutOfPollNetMap()
-			c.mu.Lock()
-			c.synced = false
-			if c.state == StateSynchronized {
-				c.state = StateAuthenticated
-			}
-			paused := c.paused
-			c.mu.Unlock()
+		err := c.direct.PollNetMap(ctx, mrs)
 
-			if paused {
-				mrs.bo.BackOff(ctx, nil)
-				c.logf("mapRoutine: paused")
-				continue
-			}
+		health.SetOutOfPollNetMap()
+		c.mu.Lock()
+		c.synced = false
+		if c.state == StateSynchronized {
+			c.state = StateAuthenticated
+		}
+		paused := c.paused
+		c.mu.Unlock()
 
-			report(err, "PollNetMap")
-			mrs.bo.BackOff(ctx, err)
+		if paused {
+			mrs.bo.BackOff(ctx, nil)
+			c.logf("mapRoutine: paused")
 			continue
 		}
+
+		report(err, "PollNetMap")
+		mrs.bo.BackOff(ctx, err)
+		continue
 	}
 }
 
@@ -735,13 +700,16 @@ func (c *Auto) Shutdown() {
 		c.closed = true
 		c.cancelAuthCtxLocked()
 		c.cancelMapCtxLocked()
+		for _, ch := range c.unpauseWaiters {
+			ch <- false
+		}
+		c.unpauseWaiters = nil
 	}
 	c.mu.Unlock()
 
 	c.logf("client.Shutdown")
 	if !closed {
 		c.unregisterHealthWatch()
-		close(c.quit)
 		<-c.authDone
 		<-c.mapDone
 		<-c.updateDone