Merge pull request #463 from Arceliar/cancellation

Cancellation

src/util/cancellation.go

@@ -0,0 +1,96 @@
+package util
+
+import (
+	"errors"
+	"runtime"
+	"sync"
+	"time"
+)
+
+type Cancellation interface {
+	Finished() <-chan struct{}
+	Cancel(error) error
+	Error() error
+}
+
+func CancellationFinalizer(c Cancellation) {
+	c.Cancel(errors.New("finalizer called"))
+}
+
+type cancellation struct {
+	signal chan error
+	cancel chan struct{}
+	errMtx sync.RWMutex
+	err    error
+}
+
+func (c *cancellation) worker() {
+	// Launch this in a separate goroutine when creating a cancellation
+	err := <-c.signal
+	c.errMtx.Lock()
+	c.err = err
+	c.errMtx.Unlock()
+	close(c.cancel)
+}
+
+func NewCancellation() Cancellation {
+	c := cancellation{
+		signal: make(chan error),
+		cancel: make(chan struct{}),
+	}
+	runtime.SetFinalizer(&c, CancellationFinalizer)
+	go c.worker()
+	return &c
+}
+
+func (c *cancellation) Finished() <-chan struct{} {
+	return c.cancel
+}
+
+func (c *cancellation) Cancel(err error) error {
+	select {
+	case c.signal <- err:
+		return nil
+	case <-c.cancel:
+		return c.Error()
+	}
+}
+
+func (c *cancellation) Error() error {
+	c.errMtx.RLock()
+	err := c.err
+	c.errMtx.RUnlock()
+	return err
+}
+
+func CancellationChild(parent Cancellation) Cancellation {
+	child := NewCancellation()
+	go func() {
+		select {
+		case <-child.Finished():
+		case <-parent.Finished():
+			child.Cancel(parent.Error())
+		}
+	}()
+	return child
+}
+
+var CancellationTimeoutError = errors.New("timeout")
+
+func CancellationWithTimeout(parent Cancellation, timeout time.Duration) Cancellation {
+	child := CancellationChild(parent)
+	go func() {
+		timer := time.NewTimer(timeout)
+		defer TimerStop(timer)
+		select {
+		case <-child.Finished():
+		case <-timer.C:
+			child.Cancel(CancellationTimeoutError)
+		}
+	}()
+	return child
+}
+
+func CancellationWithDeadline(parent Cancellation, deadline time.Time) Cancellation {
+	return CancellationWithTimeout(parent, deadline.Sub(time.Now()))
+}

src/yggdrasil/conn.go

@@ -46,13 +46,13 @@ func (e *ConnError) Closed() bool {
 
 type Conn struct {
 	core          *Core
-	nodeID        *crypto.NodeID
-	nodeMask      *crypto.NodeID
-	mutex         sync.RWMutex
-	close         chan bool
-	session       *sessionInfo
 	readDeadline  atomic.Value // time.Time // TODO timer
 	writeDeadline atomic.Value // time.Time // TODO timer
+	cancel        util.Cancellation
+	mutex         sync.RWMutex // protects the below
+	nodeID        *crypto.NodeID
+	nodeMask      *crypto.NodeID
+	session       *sessionInfo
 }
 
 // TODO func NewConn() that initializes additional fields as needed
@@ -62,12 +62,14 @@ func newConn(core *Core, nodeID *crypto.NodeID, nodeMask *crypto.NodeID, session
 		nodeID:   nodeID,
 		nodeMask: nodeMask,
 		session:  session,
-		close:    make(chan bool),
+		cancel:   util.NewCancellation(),
 	}
 	return &conn
 }
 
 func (c *Conn) String() string {
+	c.mutex.RLock()
+	defer c.mutex.RUnlock()
 	return fmt.Sprintf("conn=%p", c)
 }
 
@@ -111,28 +113,31 @@ func (c *Conn) search() error {
 	return nil
 }
 
-func getDeadlineTimer(value *atomic.Value) *time.Timer {
-	timer := time.NewTimer(24 * 365 * time.Hour) // FIXME for some reason setting this to 0 doesn't always let it stop and drain the channel correctly
-	util.TimerStop(timer)
+func (c *Conn) getDeadlineCancellation(value *atomic.Value) util.Cancellation {
 	if deadline, ok := value.Load().(time.Time); ok {
-		timer.Reset(time.Until(deadline))
+		// A deadline is set, so return a Cancellation that uses it
+		return util.CancellationWithDeadline(c.cancel, deadline)
+	} else {
+		// No cancellation was set, so return a child cancellation with no timeout
+		return util.CancellationChild(c.cancel)
 	}
-	return timer
 }
 
 func (c *Conn) Read(b []byte) (int, error) {
 	// Take a copy of the session object
 	sinfo := c.session
-	timer := getDeadlineTimer(&c.readDeadline)
-	defer util.TimerStop(timer)
+	cancel := c.getDeadlineCancellation(&c.readDeadline)
+	defer cancel.Cancel(nil)
 	var bs []byte
 	for {
 		// Wait for some traffic to come through from the session
 		select {
-		case <-c.close:
-			return 0, ConnError{errors.New("session closed"), false, false, true, 0}
-		case <-timer.C:
-			return 0, ConnError{errors.New("read timeout"), true, false, false, 0}
+		case <-cancel.Finished():
+			if cancel.Error() == util.CancellationTimeoutError {
+				return 0, ConnError{errors.New("read timeout"), true, false, false, 0}
+			} else {
+				return 0, ConnError{errors.New("session closed"), false, false, true, 0}
+			}
 		case p, ok := <-sinfo.recv:
 			// If the session is closed then do nothing
 			if !ok {
@@ -172,18 +177,22 @@ func (c *Conn) Read(b []byte) (int, error) {
 			// Send to worker
 			select {
 			case sinfo.worker <- workerFunc:
-			case <-c.close:
-				return 0, ConnError{errors.New("session closed"), false, false, true, 0}
-			case <-timer.C:
-				return 0, ConnError{errors.New("read timeout"), true, false, false, 0}
+			case <-cancel.Finished():
+				if cancel.Error() == util.CancellationTimeoutError {
+					return 0, ConnError{errors.New("read timeout"), true, false, false, 0}
+				} else {
+					return 0, ConnError{errors.New("session closed"), false, false, true, 0}
+				}
 			}
 			// Wait for the worker to finish
 			select {
 			case <-done: // Wait for the worker to finish, failing this can cause memory errors (util.[Get||Put]Bytes stuff)
-			case <-c.close:
-				return 0, ConnError{errors.New("session closed"), false, false, true, 0}
-			case <-timer.C:
-				return 0, ConnError{errors.New("read timeout"), true, false, false, 0}
+			case <-cancel.Finished():
+				if cancel.Error() == util.CancellationTimeoutError {
+					return 0, ConnError{errors.New("read timeout"), true, false, false, 0}
+				} else {
+					return 0, ConnError{errors.New("session closed"), false, false, true, 0}
+				}
 			}
 			// Something went wrong in the session worker so abort
 			if err != nil {
@@ -256,8 +265,8 @@ func (c *Conn) Write(b []byte) (bytesWritten int, err error) {
 		}
 	}
 	// Set up a timer so this doesn't block forever
-	timer := getDeadlineTimer(&c.writeDeadline)
-	defer util.TimerStop(timer)
+	cancel := c.getDeadlineCancellation(&c.writeDeadline)
+	defer cancel.Cancel(nil)
 	// Hand over to the session worker
 	defer func() {
 		if recover() != nil {
@@ -267,8 +276,12 @@ func (c *Conn) Write(b []byte) (bytesWritten int, err error) {
 	}() // In case we're racing with a close
 	select { // Send to worker
 	case sinfo.worker <- workerFunc:
-	case <-timer.C:
-		return 0, ConnError{errors.New("write timeout"), true, false, false, 0}
+	case <-cancel.Finished():
+		if cancel.Error() == util.CancellationTimeoutError {
+			return 0, ConnError{errors.New("write timeout"), true, false, false, 0}
+		} else {
+			return 0, ConnError{errors.New("session closed"), false, false, true, 0}
+		}
 	}
 	// Wait for the worker to finish, otherwise there are memory errors ([Get||Put]Bytes stuff)
 	<-done
@@ -287,13 +300,9 @@ func (c *Conn) Close() (err error) {
 		// Close the session, if it hasn't been closed already
 		c.core.router.doAdmin(c.session.close)
 	}
-	func() {
-		defer func() {
-			recover()
-			err = ConnError{errors.New("close failed, session already closed"), false, false, true, 0}
-		}()
-		close(c.close) // Closes reader/writer goroutines
-	}()
+	if e := c.cancel.Cancel(errors.New("connection closed")); e != nil {
+		err = ConnError{errors.New("close failed, session already closed"), false, false, true, 0}
+	}
 	return
 }