Merge pull request #306 from mholt/bug/websocket-races

fixed data races in websockets

middleware/websocket/websocket.go

@@ -4,9 +4,12 @@
 package websocket
 
 import (
+	"bufio"
+	"bytes"
 	"io"
 	"net"
 	"net/http"
+	"os"
 	"os/exec"
 	"strings"
 	"time"
@@ -88,15 +91,18 @@ func serveWS(w http.ResponseWriter, r *http.Request, config *Config) (int, error
 	defer conn.Close()
 
 	cmd := exec.Command(config.Command, config.Arguments...)
+
 	stdout, err := cmd.StdoutPipe()
 	if err != nil {
 		return http.StatusBadGateway, err
 	}
+	defer stdout.Close()
 
 	stdin, err := cmd.StdinPipe()
 	if err != nil {
 		return http.StatusBadGateway, err
 	}
+	defer stdin.Close()
 
 	metavars, err := buildEnv(cmd.Path, r)
 	if err != nil {
@@ -109,7 +115,31 @@ func serveWS(w http.ResponseWriter, r *http.Request, config *Config) (int, error
 		return http.StatusBadGateway, err
 	}
 
-	reader(conn, stdout, stdin)
+	done := make(chan struct{})
+	go pumpStdout(conn, stdout, done)
+	pumpStdin(conn, stdin)
+
+	stdin.Close() // close stdin to end the process
+
+	if err := cmd.Process.Signal(os.Interrupt); err != nil { // signal an interrupt to kill the process
+		return http.StatusInternalServerError, err
+	}
+
+	select {
+	case <-done:
+	case <-time.After(time.Second):
+		// terminate with extreme prejudice.
+		if err := cmd.Process.Signal(os.Kill); err != nil {
+			return http.StatusInternalServerError, err
+		}
+		<-done
+	}
+
+	// not sure what we want to do here.
+	// status for an "exited" process is greater
+	// than 0, but isn't really an error per se.
+	// just going to ignore it for now.
+	cmd.Wait()
 
 	return 0, nil
 }
@@ -163,63 +193,60 @@ func buildEnv(cmdPath string, r *http.Request) (metavars []string, err error) {
 	return
 }
 
-// reader is the guts of this package. It takes the stdin and stdout pipes
-// of the cmd we created in ServeWS and pipes them between the client and server
-// over websockets.
-func reader(conn *websocket.Conn, stdout io.ReadCloser, stdin io.WriteCloser) {
+// pumpStdin handles reading data from the websocket connection and writing
+// it to stdin of the process.
+func pumpStdin(conn *websocket.Conn, stdin io.WriteCloser) {
 	// Setup our connection's websocket ping/pong handlers from our const values.
+	defer conn.Close()
 	conn.SetReadLimit(maxMessageSize)
 	conn.SetReadDeadline(time.Now().Add(pongWait))
 	conn.SetPongHandler(func(string) error { conn.SetReadDeadline(time.Now().Add(pongWait)); return nil })
-	tickerChan := make(chan bool)
-	defer close(tickerChan) // make sure to close the ticker when we are done.
-	go ticker(conn, tickerChan)
-
 	for {
-		msgType, r, err := conn.NextReader()
+		_, message, err := conn.ReadMessage()
 		if err != nil {
-			if msgType == -1 {
-				return // we got a disconnect from the client. We are good to close.
-			}
-			conn.WriteControl(websocket.CloseMessage, websocket.FormatCloseMessage(websocket.CloseGoingAway, ""), time.Time{})
-			return
+			break
 		}
-
-		w, err := conn.NextWriter(msgType)
-		if err != nil {
-			conn.WriteControl(websocket.CloseMessage, websocket.FormatCloseMessage(websocket.CloseGoingAway, ""), time.Time{})
-			return
+		message = append(message, '\n')
+		if _, err := stdin.Write(message); err != nil {
+			break
 		}
+	}
+}
 
-		if _, err := io.Copy(stdin, r); err != nil {
-			conn.WriteControl(websocket.CloseMessage, websocket.FormatCloseMessage(websocket.CloseGoingAway, ""), time.Time{})
-			return
+// pumpStdout handles reading data from stdout of the process and writing
+// it to websocket connection.
+func pumpStdout(conn *websocket.Conn, stdout io.Reader, done chan struct{}) {
+	go pinger(conn, done)
+	defer func() {
+		conn.Close()
+		close(done) // make sure to close the pinger when we are done.
+	}()
+
+	s := bufio.NewScanner(stdout)
+	for s.Scan() {
+		conn.SetWriteDeadline(time.Now().Add(writeWait))
+		if err := conn.WriteMessage(websocket.TextMessage, bytes.TrimSpace(s.Bytes())); err != nil {
+			break
 		}
-
-		go func() {
-			if _, err := io.Copy(w, stdout); err != nil {
-				conn.WriteControl(websocket.CloseMessage, websocket.FormatCloseMessage(websocket.CloseGoingAway, ""), time.Time{})
-				return
-			}
-			if err := w.Close(); err != nil {
-				conn.WriteControl(websocket.CloseMessage, websocket.FormatCloseMessage(websocket.CloseGoingAway, ""), time.Time{})
-				return
-			}
-		}()
+	}
+	if s.Err() != nil {
+		conn.WriteControl(websocket.CloseMessage, websocket.FormatCloseMessage(websocket.CloseGoingAway, s.Err().Error()), time.Time{})
 	}
 }
 
-// ticker is start by the reader. Basically it is the method that simulates the websocket
-// between the server and client to keep it alive with ping messages.
-func ticker(conn *websocket.Conn, c chan bool) {
+// pinger simulates the websocket to keep it alive with ping messages.
+func pinger(conn *websocket.Conn, done chan struct{}) {
 	ticker := time.NewTicker(pingPeriod)
 	defer ticker.Stop()
 
 	for { // blocking loop with select to wait for stimulation.
 		select {
 		case <-ticker.C:
-			conn.WriteMessage(websocket.PingMessage, nil)
-		case <-c:
+			if err := conn.WriteControl(websocket.PingMessage, []byte{}, time.Now().Add(writeWait)); err != nil {
+				conn.WriteControl(websocket.CloseMessage, websocket.FormatCloseMessage(websocket.CloseGoingAway, err.Error()), time.Time{})
+				return
+			}
+		case <-done:
 			return // clean up this routine.
 		}
 	}