Merge pull request #8062 from vishh/run_in_phase2

Add support for 'docker exec' - phase 2

api/client/commands.go

@@ -625,7 +625,7 @@ func (cli *DockerCli) CmdStart(args ...string) error {
 		v.Set("stderr", "1")
 
 		cErr = utils.Go(func() error {
-			return cli.hijack("POST", "/containers/"+cmd.Arg(0)+"/attach?"+v.Encode(), tty, in, cli.out, cli.err, nil)
+			return cli.hijack("POST", "/containers/"+cmd.Arg(0)+"/attach?"+v.Encode(), tty, in, cli.out, cli.err, nil, nil)
 		})
 	}
 
@@ -653,7 +653,7 @@ func (cli *DockerCli) CmdStart(args ...string) error {
 
 	if *openStdin || *attach {
 		if tty && cli.isTerminal {
-			if err := cli.monitorTtySize(cmd.Arg(0)); err != nil {
+			if err := cli.monitorTtySize(cmd.Arg(0), false); err != nil {
 				log.Errorf("Error monitoring TTY size: %s", err)
 			}
 		}
@@ -1805,7 +1805,7 @@ func (cli *DockerCli) CmdAttach(args ...string) error {
 	)
 
 	if tty && cli.isTerminal {
-		if err := cli.monitorTtySize(cmd.Arg(0)); err != nil {
+		if err := cli.monitorTtySize(cmd.Arg(0), false); err != nil {
 			log.Debugf("Error monitoring TTY size: %s", err)
 		}
 	}
@@ -1827,7 +1827,7 @@ func (cli *DockerCli) CmdAttach(args ...string) error {
 		defer signal.StopCatch(sigc)
 	}
 
-	if err := cli.hijack("POST", "/containers/"+cmd.Arg(0)+"/attach?"+v.Encode(), tty, in, cli.out, cli.err, nil); err != nil {
+	if err := cli.hijack("POST", "/containers/"+cmd.Arg(0)+"/attach?"+v.Encode(), tty, in, cli.out, cli.err, nil, nil); err != nil {
 		return err
 	}
 
@@ -2109,7 +2109,7 @@ func (cli *DockerCli) CmdRun(args ...string) error {
 		}
 
 		errCh = utils.Go(func() error {
-			return cli.hijack("POST", "/containers/"+runResult.Get("Id")+"/attach?"+v.Encode(), config.Tty, in, out, stderr, hijacked)
+			return cli.hijack("POST", "/containers/"+runResult.Get("Id")+"/attach?"+v.Encode(), config.Tty, in, out, stderr, hijacked, nil)
 		})
 	} else {
 		close(hijacked)
@@ -2136,7 +2136,7 @@ func (cli *DockerCli) CmdRun(args ...string) error {
 	}
 
 	if (config.AttachStdin || config.AttachStdout || config.AttachStderr) && config.Tty && cli.isTerminal {
-		if err := cli.monitorTtySize(runResult.Get("Id")); err != nil {
+		if err := cli.monitorTtySize(runResult.Get("Id"), false); err != nil {
 			log.Errorf("Error monitoring TTY size: %s", err)
 		}
 	}
@@ -2299,3 +2299,101 @@ func (cli *DockerCli) CmdLoad(args ...string) error {
 	}
 	return nil
 }
+
+func (cli *DockerCli) CmdExec(args ...string) error {
+	cmd := cli.Subcmd("exec", "CONTAINER COMMAND [ARG...]", "Run a command in an existing container")
+
+	execConfig, err := runconfig.ParseExec(cmd, args)
+	if err != nil {
+		return err
+	}
+	if execConfig.Container == "" {
+		cmd.Usage()
+		return nil
+	}
+
+	stream, _, err := cli.call("POST", "/containers/"+execConfig.Container+"/exec", execConfig, false)
+	if err != nil {
+		return err
+	}
+
+	var execResult engine.Env
+	if err := execResult.Decode(stream); err != nil {
+		return err
+	}
+
+	execID := execResult.Get("Id")
+
+	if execID == "" {
+		fmt.Fprintf(cli.out, "exec ID empty")
+		return nil
+	}
+
+	if execConfig.Detach {
+		if _, _, err := readBody(cli.call("POST", "/exec/"+execID+"/start", execConfig, false)); err != nil {
+			return err
+		}
+		return nil
+	}
+
+	// Interactive exec requested.
+	var (
+		out, stderr io.Writer
+		in          io.ReadCloser
+		hijacked    = make(chan io.Closer)
+		errCh       chan error
+	)
+
+	// Block the return until the chan gets closed
+	defer func() {
+		log.Debugf("End of CmdExec(), Waiting for hijack to finish.")
+		if _, ok := <-hijacked; ok {
+			log.Errorf("Hijack did not finish (chan still open)")
+		}
+	}()
+
+	if execConfig.AttachStdin {
+		in = cli.in
+	}
+	if execConfig.AttachStdout {
+		out = cli.out
+	}
+	if execConfig.AttachStderr {
+		if execConfig.Tty {
+			stderr = cli.out
+		} else {
+			stderr = cli.err
+		}
+	}
+	errCh = utils.Go(func() error {
+		return cli.hijack("POST", "/exec/"+execID+"/start", execConfig.Tty, in, out, stderr, hijacked, execConfig)
+	})
+
+	// Acknowledge the hijack before starting
+	select {
+	case closer := <-hijacked:
+		// Make sure that hijack gets closed when returning. (result
+		// in closing hijack chan and freeing server's goroutines.
+		if closer != nil {
+			defer closer.Close()
+		}
+	case err := <-errCh:
+		if err != nil {
+			log.Debugf("Error hijack: %s", err)
+			return err
+		}
+	}
+
+	if execConfig.Tty && cli.isTerminal {
+		if err := cli.monitorTtySize(execID, true); err != nil {
+			log.Errorf("Error monitoring TTY size: %s", err)
+		}
+	}
+
+	if err := <-errCh; err != nil {
+		log.Debugf("Error hijack: %s", err)
+		return err
+	}
+
+	return nil
+}

api/client/hijack.go

@@ -25,14 +25,18 @@ func (cli *DockerCli) dial() (net.Conn, error) {
 	return net.Dial(cli.proto, cli.addr)
 }
 
-func (cli *DockerCli) hijack(method, path string, setRawTerminal bool, in io.ReadCloser, stdout, stderr io.Writer, started chan io.Closer) error {
+func (cli *DockerCli) hijack(method, path string, setRawTerminal bool, in io.ReadCloser, stdout, stderr io.Writer, started chan io.Closer, data interface{}) error {
 	defer func() {
 		if started != nil {
 			close(started)
 		}
 	}()
 
-	req, err := http.NewRequest(method, fmt.Sprintf("/v%s%s", api.APIVERSION, path), nil)
+	params, err := cli.encodeData(data)
+	if err != nil {
+		return err
+	}
+	req, err := http.NewRequest(method, fmt.Sprintf("/v%s%s", api.APIVERSION, path), params)
 	if err != nil {
 		return err
 	}

api/client/utils.go

@@ -40,24 +40,31 @@ func (cli *DockerCli) HTTPClient() *http.Client {
 	return &http.Client{Transport: tr}
 }
 
-func (cli *DockerCli) call(method, path string, data interface{}, passAuthInfo bool) (io.ReadCloser, int, error) {
+func (cli *DockerCli) encodeData(data interface{}) (*bytes.Buffer, error) {
 	params := bytes.NewBuffer(nil)
 	if data != nil {
 		if env, ok := data.(engine.Env); ok {
 			if err := env.Encode(params); err != nil {
-				return nil, -1, err
+				return nil, err
 			}
 		} else {
 			buf, err := json.Marshal(data)
 			if err != nil {
-				return nil, -1, err
+				return nil, err
 			}
 			if _, err := params.Write(buf); err != nil {
+				return nil, err
+			}
+		}
+	}
+	return params, nil
+}
+
+func (cli *DockerCli) call(method, path string, data interface{}, passAuthInfo bool) (io.ReadCloser, int, error) {
+	params, err := cli.encodeData(data)
+	if err != nil {
 		return nil, -1, err
 	}
-		}
-	}
-
 	req, err := http.NewRequest(method, fmt.Sprintf("/v%s%s", api.APIVERSION, path), params)
 	if err != nil {
 		return nil, -1, err
@@ -108,6 +115,7 @@ func (cli *DockerCli) call(method, path string, data interface{}, passAuthInfo b
 		}
 		return nil, resp.StatusCode, fmt.Errorf("Error response from daemon: %s", bytes.TrimSpace(body))
 	}
+
 	return resp.Body, resp.StatusCode, nil
 }
 
@@ -172,7 +180,7 @@ func (cli *DockerCli) streamHelper(method, path string, setRawTerminal bool, in
 	return nil
 }
 
-func (cli *DockerCli) resizeTty(id string) {
+func (cli *DockerCli) resizeTty(id string, isExec bool) {
 	height, width := cli.getTtySize()
 	if height == 0 && width == 0 {
 		return
@@ -180,7 +188,15 @@ func (cli *DockerCli) resizeTty(id string) {
 	v := url.Values{}
 	v.Set("h", strconv.Itoa(height))
 	v.Set("w", strconv.Itoa(width))
-	if _, _, err := readBody(cli.call("POST", "/containers/"+id+"/resize?"+v.Encode(), nil, false)); err != nil {
+
+	path := ""
+	if !isExec {
+		path = "/containers/" + id + "/resize?"
+	} else {
+		path = "/exec/" + id + "/resize?"
+	}
+
+	if _, _, err := readBody(cli.call("POST", path+v.Encode(), nil, false)); err != nil {
 		log.Debugf("Error resize: %s", err)
 	}
 }
@@ -219,14 +235,14 @@ func getExitCode(cli *DockerCli, containerId string) (bool, int, error) {
 	return state.GetBool("Running"), state.GetInt("ExitCode"), nil
 }
 
-func (cli *DockerCli) monitorTtySize(id string) error {
+func (cli *DockerCli) monitorTtySize(id string, isExec bool) error {
-	cli.resizeTty(id)
+	cli.resizeTty(id, isExec)
 
 	sigchan := make(chan os.Signal, 1)
 	gosignal.Notify(sigchan, syscall.SIGWINCH)
 	go func() {
 		for _ = range sigchan {
-			cli.resizeTty(id)
+			cli.resizeTty(id, isExec)
 		}
 	}()
 	return nil

api/server/server.go

@@ -663,6 +663,7 @@ func postContainersCreate(eng *engine.Engine, version version.Version, w http.Re
 	}
 	out.Set("Id", engine.Tail(stdoutBuffer, 1))
 	out.SetList("Warnings", outWarnings)
+
 	return writeJSON(w, http.StatusCreated, out)
 }
 
@@ -1026,6 +1027,103 @@ func postContainersCopy(eng *engine.Engine, version version.Version, w http.Resp
 	return nil
 }
 
+func postContainerExecCreate(eng *engine.Engine, version version.Version, w http.ResponseWriter, r *http.Request, vars map[string]string) error {
+	if err := parseForm(r); err != nil {
+		return nil
+	}
+	var (
+		out          engine.Env
+		name         = vars["name"]
+		job          = eng.Job("execCreate", name)
+		stdoutBuffer = bytes.NewBuffer(nil)
+	)
+	if err := job.DecodeEnv(r.Body); err != nil {
+		return err
+	}
+
+	job.Stdout.Add(stdoutBuffer)
+	// Register an instance of Exec in container.
+	if err := job.Run(); err != nil {
+		fmt.Fprintf(os.Stderr, "Error setting up exec command in container %s: %s\n", name, err)
+		return err
+	}
+	// Return the ID
+	out.Set("Id", engine.Tail(stdoutBuffer, 1))
+
+	return writeJSON(w, http.StatusCreated, out)
+}
+
+func postContainerExecStart(eng *engine.Engine, version version.Version, w http.ResponseWriter, r *http.Request, vars map[string]string) error {
+	if err := parseForm(r); err != nil {
+		return nil
+	}
+	var (
+		name             = vars["name"]
+		job              = eng.Job("execStart", name)
+		errOut io.Writer = os.Stderr
+	)
+	if err := job.DecodeEnv(r.Body); err != nil {
+		return err
+	}
+	if !job.GetenvBool("Detach") {
+		// Setting up the streaming http interface.
+		inStream, outStream, err := hijackServer(w)
+		if err != nil {
+			return err
+		}
+
+		defer func() {
+			if tcpc, ok := inStream.(*net.TCPConn); ok {
+				tcpc.CloseWrite()
+			} else {
+				inStream.Close()
+			}
+		}()
+		defer func() {
+			if tcpc, ok := outStream.(*net.TCPConn); ok {
+				tcpc.CloseWrite()
+			} else if closer, ok := outStream.(io.Closer); ok {
+				closer.Close()
+			}
+		}()
+
+		var errStream io.Writer
+
+		fmt.Fprintf(outStream, "HTTP/1.1 200 OK\r\nContent-Type: application/vnd.docker.raw-stream\r\n\r\n")
+		if !job.GetenvBool("Tty") && version.GreaterThanOrEqualTo("1.6") {
+			errStream = utils.NewStdWriter(outStream, utils.Stderr)
+			outStream = utils.NewStdWriter(outStream, utils.Stdout)
+		} else {
+			errStream = outStream
+		}
+		job.Stdin.Add(inStream)
+		job.Stdout.Add(outStream)
+		job.Stderr.Set(errStream)
+		errOut = outStream
+	}
+	// Now run the user process in container.
+	job.SetCloseIO(false)
+	if err := job.Run(); err != nil {
+		fmt.Fprintf(errOut, "Error starting exec command in container %s: %s\n", name, err)
+		return err
+	}
+	w.WriteHeader(http.StatusNoContent)
+	return nil
+}
+
+func postContainerExecResize(eng *engine.Engine, version version.Version, w http.ResponseWriter, r *http.Request, vars map[string]string) error {
+	if err := parseForm(r); err != nil {
+		return err
+	}
+	if vars == nil {
+		return fmt.Errorf("Missing parameter")
+	}
+	if err := eng.Job("execResize", vars["name"], r.Form.Get("h"), r.Form.Get("w")).Run(); err != nil {
+		return err
+	}
+	return nil
+}
+
 func optionsHandler(eng *engine.Engine, version version.Version, w http.ResponseWriter, r *http.Request, vars map[string]string) error {
 	w.WriteHeader(http.StatusOK)
 	return nil
@@ -1148,6 +1246,9 @@ func createRouter(eng *engine.Engine, logging, enableCors bool, dockerVersion st
 			"/containers/{name:.*}/resize":  postContainersResize,
 			"/containers/{name:.*}/attach":  postContainersAttach,
 			"/containers/{name:.*}/copy":    postContainersCopy,
+			"/containers/{name:.*}/exec":    postContainerExecCreate,
+			"/exec/{name:.*}/start":         postContainerExecStart,
+			"/exec/{name:.*}/resize":        postContainerExecResize,
 		},
 		"DELETE": {
 			"/containers/{name:.*}": deleteContainers,
@@ -1334,6 +1435,7 @@ func ListenAndServe(proto, addr string, job *engine.Job) error {
 					return err
 				}
 			}
+
 		}
 		if err := os.Chmod(addr, 0660); err != nil {
 			return err

builder/internals.go

@@ -407,7 +407,7 @@ func (b *Builder) run(c *daemon.Container) error {
 			// FIXME (LK4D4): Also, maybe makes sense to call "logs" job, it is like attach
 			// but without hijacking for stdin. Also, with attach there can be race
 			// condition because of some output already was printed before it.
-			return <-b.Daemon.Attach(c, nil, nil, b.OutStream, b.ErrStream)
+			return <-b.Daemon.Attach(&c.StreamConfig, c.Config.OpenStdin, c.Config.StdinOnce, c.Config.Tty, nil, nil, b.OutStream, b.ErrStream)
 		})
 	}
 

daemon/attach.go

@@ -103,7 +103,7 @@ func (daemon *Daemon) ContainerAttach(job *engine.Job) engine.Status {
 			cStderr = job.Stderr
 		}
 
-		<-daemon.Attach(container, cStdin, cStdinCloser, cStdout, cStderr)
+		<-daemon.Attach(&container.StreamConfig, container.Config.OpenStdin, container.Config.StdinOnce, container.Config.Tty, cStdin, cStdinCloser, cStdout, cStderr)
 		// If we are in stdinonce mode, wait for the process to end
 		// otherwise, simply return
 		if container.Config.StdinOnce && !container.Config.Tty {
@@ -119,23 +119,25 @@ func (daemon *Daemon) ContainerAttach(job *engine.Job) engine.Status {
 // Attach and ContainerAttach.
 //
 // This method is in use by builder/builder.go.
-func (daemon *Daemon) Attach(container *Container, stdin io.ReadCloser, stdinCloser io.Closer, stdout io.Writer, stderr io.Writer) chan error {
+func (daemon *Daemon) Attach(streamConfig *StreamConfig, openStdin, stdinOnce, tty bool, stdin io.ReadCloser, stdinCloser io.Closer, stdout io.Writer, stderr io.Writer) chan error {
 	var (
 		cStdout, cStderr io.ReadCloser
 		nJobs            int
 		errors           = make(chan error, 3)
 	)
 
-	if stdin != nil && container.Config.OpenStdin {
+	// Connect stdin of container to the http conn.
+	if stdin != nil && openStdin {
 		nJobs++
-		if cStdin, err := container.StdinPipe(); err != nil {
+		// Get the stdin pipe.
+		if cStdin, err := streamConfig.StdinPipe(); err != nil {
 			errors <- err
 		} else {
 			go func() {
 				log.Debugf("attach: stdin: begin")
 				defer log.Debugf("attach: stdin: end")
 				// No matter what, when stdin is closed (io.Copy unblock), close stdout and stderr
-				if container.Config.StdinOnce && !container.Config.Tty {
+				if stdinOnce && !tty {
 					defer cStdin.Close()
 				} else {
 					defer func() {
@@ -147,10 +149,11 @@ func (daemon *Daemon) Attach(container *Container, stdin io.ReadCloser, stdinClo
 						}
 					}()
 				}
-				if container.Config.Tty {
+				if tty {
 					_, err = utils.CopyEscapable(cStdin, stdin)
 				} else {
 					_, err = io.Copy(cStdin, stdin)
+
 				}
 				if err == io.ErrClosedPipe {
 					err = nil
@@ -164,7 +167,8 @@ func (daemon *Daemon) Attach(container *Container, stdin io.ReadCloser, stdinClo
 	}
 	if stdout != nil {
 		nJobs++
-		if p, err := container.StdoutPipe(); err != nil {
+		// Get a reader end of a pipe that is attached as stdout to the container.
+		if p, err := streamConfig.StdoutPipe(); err != nil {
 			errors <- err
 		} else {
 			cStdout = p
@@ -172,7 +176,7 @@ func (daemon *Daemon) Attach(container *Container, stdin io.ReadCloser, stdinClo
 				log.Debugf("attach: stdout: begin")
 				defer log.Debugf("attach: stdout: end")
 				// If we are in StdinOnce mode, then close stdin
-				if container.Config.StdinOnce && stdin != nil {
+				if stdinOnce && stdin != nil {
 					defer stdin.Close()
 				}
 				if stdinCloser != nil {
@@ -189,11 +193,12 @@ func (daemon *Daemon) Attach(container *Container, stdin io.ReadCloser, stdinClo
 			}()
 		}
 	} else {
+		// Point stdout of container to a no-op writer.
 		go func() {
 			if stdinCloser != nil {
 				defer stdinCloser.Close()
 			}
-			if cStdout, err := container.StdoutPipe(); err != nil {
+			if cStdout, err := streamConfig.StdoutPipe(); err != nil {
 				log.Errorf("attach: stdout pipe: %s", err)
 			} else {
 				io.Copy(&ioutils.NopWriter{}, cStdout)
@@ -202,7 +207,7 @@ func (daemon *Daemon) Attach(container *Container, stdin io.ReadCloser, stdinClo
 	}
 	if stderr != nil {
 		nJobs++
-		if p, err := container.StderrPipe(); err != nil {
+		if p, err := streamConfig.StderrPipe(); err != nil {
 			errors <- err
 		} else {
 			cStderr = p
@@ -210,7 +215,8 @@ func (daemon *Daemon) Attach(container *Container, stdin io.ReadCloser, stdinClo
 				log.Debugf("attach: stderr: begin")
 				defer log.Debugf("attach: stderr: end")
 				// If we are in StdinOnce mode, then close stdin
-				if container.Config.StdinOnce && stdin != nil {
+				// Why are we closing stdin here and above while handling stdout?
+				if stdinOnce && stdin != nil {
 					defer stdin.Close()
 				}
 				if stdinCloser != nil {
@@ -227,12 +233,13 @@ func (daemon *Daemon) Attach(container *Container, stdin io.ReadCloser, stdinClo
 			}()
 		}
 	} else {
+		// Point stderr at a no-op writer.
 		go func() {
 			if stdinCloser != nil {
 				defer stdinCloser.Close()
 			}
 
-			if cStderr, err := container.StderrPipe(); err != nil {
+			if cStderr, err := streamConfig.StderrPipe(); err != nil {
 				log.Errorf("attach: stdout pipe: %s", err)
 			} else {
 				io.Copy(&ioutils.NopWriter{}, cStderr)

daemon/container.go

@@ -88,6 +88,7 @@ type Container struct {
 
 	activeLinks  map[string]*links.Link
 	monitor      *containerMonitor
+	execCommands *execStore
 }
 
 func (container *Container) FromDisk() error {

daemon/daemon.go

@@ -85,6 +85,7 @@ type Daemon struct {
 	repository     string
 	sysInitPath    string
 	containers     *contStore
+	execCommands   *execStore
 	graph          *graph.Graph
 	repositories   *graph.TagStore
 	idIndex        *truncindex.TruncIndex
@@ -122,6 +123,9 @@ func (daemon *Daemon) Install(eng *engine.Engine) error {
 		"unpause":           daemon.ContainerUnpause,
 		"wait":              daemon.ContainerWait,
 		"image_delete":      daemon.ImageDelete, // FIXME: see above
+		"execCreate":        daemon.ContainerExecCreate,
+		"execStart":         daemon.ContainerExecStart,
+		"execResize":        daemon.ContainerExecResize,
 	} {
 		if err := eng.Register(name, method); err != nil {
 			return err
@@ -496,17 +500,17 @@ func (daemon *Daemon) generateHostname(id string, config *runconfig.Config) {
 	}
 }
 
-func (daemon *Daemon) getEntrypointAndArgs(config *runconfig.Config) (string, []string) {
+func (daemon *Daemon) getEntrypointAndArgs(configEntrypoint, configCmd []string) (string, []string) {
 	var (
 		entrypoint string
 		args       []string
 	)
-	if len(config.Entrypoint) != 0 {
+	if len(configEntrypoint) != 0 {
-		entrypoint = config.Entrypoint[0]
+		entrypoint = configEntrypoint[0]
-		args = append(config.Entrypoint[1:], config.Cmd...)
+		args = append(configEntrypoint[1:], configCmd...)
 	} else {
-		entrypoint = config.Cmd[0]
+		entrypoint = configCmd[0]
-		args = config.Cmd[1:]
+		args = configCmd[1:]
 	}
 	return entrypoint, args
 }
@@ -522,7 +526,7 @@ func (daemon *Daemon) newContainer(name string, config *runconfig.Config, img *i
 	}
 
 	daemon.generateHostname(id, config)
-	entrypoint, args := daemon.getEntrypointAndArgs(config)
+	entrypoint, args := daemon.getEntrypointAndArgs(config.Entrypoint, config.Cmd)
 
 	container := &Container{
 		// FIXME: we should generate the ID here instead of receiving it as an argument
@@ -538,6 +542,7 @@ func (daemon *Daemon) newContainer(name string, config *runconfig.Config, img *i
 		Driver:          daemon.driver.String(),
 		ExecDriver:      daemon.execDriver.Name(),
 		State:           NewState(),
+		execCommands:    newExecStore(),
 	}
 	container.root = daemon.containerRoot(container.ID)
 
@@ -846,6 +851,7 @@ func NewDaemonFromDirectory(config *Config, eng *engine.Engine) (*Daemon, error)
 	daemon := &Daemon{
 		repository:     daemonRepo,
 		containers:     &contStore{s: make(map[string]*Container)},
+		execCommands:   newExecStore(),
 		graph:          g,
 		repositories:   repositories,
 		idIndex:        truncindex.NewTruncIndex([]string{}),

daemon/exec.go

@@ -0,0 +1,294 @@
+// build linux
+
+package daemon
+
+import (
+	"fmt"
+	"io"
+	"io/ioutil"
+	"sync"
+
+	"github.com/docker/docker/daemon/execdriver"
+	"github.com/docker/docker/engine"
+	"github.com/docker/docker/pkg/broadcastwriter"
+	"github.com/docker/docker/pkg/ioutils"
+	"github.com/docker/docker/pkg/log"
+	"github.com/docker/docker/runconfig"
+	"github.com/docker/docker/utils"
+)
+
+type execConfig struct {
+	sync.Mutex
+	ID            string
+	Running       bool
+	ProcessConfig execdriver.ProcessConfig
+	StreamConfig
+	OpenStdin  bool
+	OpenStderr bool
+	OpenStdout bool
+	Container  *Container
+}
+
+type execStore struct {
+	s map[string]*execConfig
+	sync.Mutex
+}
+
+func newExecStore() *execStore {
+	return &execStore{s: make(map[string]*execConfig, 0)}
+}
+
+func (e *execStore) Add(id string, execConfig *execConfig) {
+	e.Lock()
+	e.s[id] = execConfig
+	e.Unlock()
+}
+
+func (e *execStore) Get(id string) *execConfig {
+	e.Lock()
+	res := e.s[id]
+	e.Unlock()
+	return res
+}
+
+func (e *execStore) Delete(id string) {
+	e.Lock()
+	delete(e.s, id)
+	e.Unlock()
+}
+
+func (execConfig *execConfig) Resize(h, w int) error {
+	return execConfig.ProcessConfig.Terminal.Resize(h, w)
+}
+
+func (d *Daemon) registerExecCommand(execConfig *execConfig) {
+	// Storing execs in container inorder to kill them gracefully whenever the container is stopped or removed.
+	execConfig.Container.execCommands.Add(execConfig.ID, execConfig)
+	// Storing execs in daemon for easy access via remote API.
+	d.execCommands.Add(execConfig.ID, execConfig)
+}
+
+func (d *Daemon) getExecConfig(name string) (*execConfig, error) {
+	if execConfig := d.execCommands.Get(name); execConfig != nil {
+		if !execConfig.Container.IsRunning() {
+			return nil, fmt.Errorf("Container %s is not not running", execConfig.Container.ID)
+		}
+		return execConfig, nil
+	}
+
+	return nil, fmt.Errorf("No exec '%s' in found in daemon", name)
+}
+
+func (d *Daemon) unregisterExecCommand(execConfig *execConfig) {
+	execConfig.Container.execCommands.Delete(execConfig.ID)
+	d.execCommands.Delete(execConfig.ID)
+}
+
+func (d *Daemon) getActiveContainer(name string) (*Container, error) {
+	container := d.Get(name)
+
+	if container == nil {
+		return nil, fmt.Errorf("No such container: %s", name)
+	}
+
+	if !container.IsRunning() {
+		return nil, fmt.Errorf("Container %s is not not running", name)
+	}
+
+	return container, nil
+}
+
+func (d *Daemon) ContainerExecCreate(job *engine.Job) engine.Status {
+	if len(job.Args) != 1 {
+		return job.Errorf("Usage: %s [options] container command [args]", job.Name)
+	}
+
+	var name = job.Args[0]
+
+	container, err := d.getActiveContainer(name)
+	if err != nil {
+		return job.Error(err)
+	}
+
+	config := runconfig.ExecConfigFromJob(job)
+
+	entrypoint, args := d.getEntrypointAndArgs(nil, config.Cmd)
+
+	processConfig := execdriver.ProcessConfig{
+		Privileged: config.Privileged,
+		User:       config.User,
+		Tty:        config.Tty,
+		Entrypoint: entrypoint,
+		Arguments:  args,
+	}
+
+	execConfig := &execConfig{
+		ID:            utils.GenerateRandomID(),
+		OpenStdin:     config.AttachStdin,
+		OpenStdout:    config.AttachStdout,
+		OpenStderr:    config.AttachStderr,
+		StreamConfig:  StreamConfig{},
+		ProcessConfig: processConfig,
+		Container:     container,
+		Running:       false,
+	}
+
+	d.registerExecCommand(execConfig)
+
+	job.Printf("%s\n", execConfig.ID)
+
+	return engine.StatusOK
+}
+
+func (d *Daemon) ContainerExecStart(job *engine.Job) engine.Status {
+	if len(job.Args) != 1 {
+		return job.Errorf("Usage: %s [options] exec", job.Name)
+	}
+
+	var (
+		cStdin           io.ReadCloser
+		cStdout, cStderr io.Writer
+		cStdinCloser     io.Closer
+		execName         = job.Args[0]
+	)
+
+	execConfig, err := d.getExecConfig(execName)
+	if err != nil {
+		return job.Error(err)
+	}
+
+	func() {
+		execConfig.Lock()
+		defer execConfig.Unlock()
+		if execConfig.Running {
+			err = fmt.Errorf("Error: Exec command %s is already running", execName)
+		}
+		execConfig.Running = true
+	}()
+	if err != nil {
+		return job.Error(err)
+	}
+
+	log.Debugf("starting exec command %s in container %s", execConfig.ID, execConfig.Container.ID)
+	container := execConfig.Container
+
+	if execConfig.OpenStdin {
+		r, w := io.Pipe()
+		go func() {
+			defer w.Close()
+			io.Copy(w, job.Stdin)
+		}()
+		cStdin = r
+		cStdinCloser = job.Stdin
+	}
+	if execConfig.OpenStdout {
+		cStdout = job.Stdout
+	}
+	if execConfig.OpenStderr {
+		cStderr = job.Stderr
+	}
+
+	execConfig.StreamConfig.stderr = broadcastwriter.New()
+	execConfig.StreamConfig.stdout = broadcastwriter.New()
+	// Attach to stdin
+	if execConfig.OpenStdin {
+		execConfig.StreamConfig.stdin, execConfig.StreamConfig.stdinPipe = io.Pipe()
+	} else {
+		execConfig.StreamConfig.stdinPipe = ioutils.NopWriteCloser(ioutil.Discard) // Silently drop stdin
+	}
+
+	attachErr := d.Attach(&execConfig.StreamConfig, execConfig.OpenStdin, false, execConfig.ProcessConfig.Tty, cStdin, cStdinCloser, cStdout, cStderr)
+
+	execErr := make(chan error)
+
+	// Remove exec from daemon and container.
+	defer d.unregisterExecCommand(execConfig)
+
+	go func() {
+		err := container.Exec(execConfig)
+		if err != nil {
+			execErr <- fmt.Errorf("Cannot run exec command %s in container %s: %s", execName, container.ID, err)
+		}
+	}()
+
+	select {
+	case err := <-attachErr:
+		if err != nil {
+			return job.Errorf("attach failed with error: %s", err)
+		}
+		break
+	case err := <-execErr:
+		return job.Error(err)
+	}
+
+	return engine.StatusOK
+}
+
+func (d *Daemon) Exec(c *Container, execConfig *execConfig, pipes *execdriver.Pipes, startCallback execdriver.StartCallback) (int, error) {
+	return d.execDriver.Exec(c.command, &execConfig.ProcessConfig, pipes, startCallback)
+}
+
+func (container *Container) Exec(execConfig *execConfig) error {
+	container.Lock()
+	defer container.Unlock()
+
+	waitStart := make(chan struct{})
+
+	callback := func(processConfig *execdriver.ProcessConfig, pid int) {
+		if processConfig.Tty {
+			// The callback is called after the process Start()
+			// so we are in the parent process. In TTY mode, stdin/out/err is the PtySlace
+			// which we close here.
+			if c, ok := processConfig.Stdout.(io.Closer); ok {
+				c.Close()
+			}
+		}
+		close(waitStart)
+	}
+
+	// We use a callback here instead of a goroutine and an chan for
+	// syncronization purposes
+	cErr := utils.Go(func() error { return container.monitorExec(execConfig, callback) })
+
+	// Exec should not return until the process is actually running
+	select {
+	case <-waitStart:
+	case err := <-cErr:
+		return err
+	}
+
+	return nil
+}
+
+func (container *Container) monitorExec(execConfig *execConfig, callback execdriver.StartCallback) error {
+	var (
+		err      error
+		exitCode int
+	)
+
+	pipes := execdriver.NewPipes(execConfig.StreamConfig.stdin, execConfig.StreamConfig.stdout, execConfig.StreamConfig.stderr, execConfig.OpenStdin)
+	exitCode, err = container.daemon.Exec(container, execConfig, pipes, callback)
+	if err != nil {
+		log.Errorf("Error running command in existing container %s: %s", container.ID, err)
+	}
+
+	log.Debugf("Exec task in container %s exited with code %d", container.ID, exitCode)
+	if execConfig.OpenStdin {
+		if err := execConfig.StreamConfig.stdin.Close(); err != nil {
+			log.Errorf("Error closing stdin while running in %s: %s", container.ID, err)
+		}
+	}
+	if err := execConfig.StreamConfig.stdout.Clean(); err != nil {
+		log.Errorf("Error closing stdout while running in %s: %s", container.ID, err)
+	}
+	if err := execConfig.StreamConfig.stderr.Clean(); err != nil {
+		log.Errorf("Error closing stderr while running in %s: %s", container.ID, err)
+	}
+	if execConfig.ProcessConfig.Terminal != nil {
+		if err := execConfig.ProcessConfig.Terminal.Close(); err != nil {
+			log.Errorf("Error closing terminal while running in container %s: %s", container.ID, err)
+		}
+	}
+
+	return err
+}

daemon/execdriver/driver.go

@@ -42,6 +42,8 @@ type TtyTerminal interface {
 
 type Driver interface {
 	Run(c *Command, pipes *Pipes, startCallback StartCallback) (int, error) // Run executes the process and blocks until the process exits and returns the exit code
+	// Exec executes the process in an existing container, blocks until the process exits and returns the exit code
+	Exec(c *Command, processConfig *ProcessConfig, pipes *Pipes, startCallback StartCallback) (int, error)
 	Kill(c *Command, sig int) error
 	Pause(c *Command) error
 	Unpause(c *Command) error

daemon/execdriver/lxc/driver.go

@@ -527,3 +527,7 @@ func (t *TtyConsole) Close() error {
 	t.SlavePty.Close()
 	return t.MasterPty.Close()
 }
+
+func (d *driver) Exec(c *execdriver.Command, processConfig *execdriver.ProcessConfig, pipes *execdriver.Pipes, startCallback execdriver.StartCallback) (int, error) {
+	return -1, fmt.Errorf("Unsupported: Exec is not supported by the lxc driver")
+}

daemon/execdriver/native/driver.go

@@ -22,6 +22,7 @@ import (
 	"github.com/docker/libcontainer/cgroups/systemd"
 	consolepkg "github.com/docker/libcontainer/console"
 	"github.com/docker/libcontainer/namespaces"
+	_ "github.com/docker/libcontainer/namespaces/nsenter"
 	"github.com/docker/libcontainer/system"
 )
 

daemon/execdriver/native/exec.go

@@ -0,0 +1,70 @@
+// +build linux
+
+package native
+
+import (
+	"fmt"
+	"log"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"runtime"
+
+	"github.com/docker/docker/daemon/execdriver"
+	"github.com/docker/docker/reexec"
+	"github.com/docker/libcontainer"
+	"github.com/docker/libcontainer/namespaces"
+)
+
+const execCommandName = "nsenter-exec"
+
+func init() {
+	reexec.Register(execCommandName, nsenterExec)
+}
+
+func nsenterExec() {
+	runtime.LockOSThread()
+
+	// User args are passed after '--' in the command line.
+	userArgs := findUserArgs()
+
+	config, err := loadConfigFromFd()
+	if err != nil {
+		log.Fatalf("docker-exec: unable to receive config from sync pipe: %s", err)
+	}
+
+	if err := namespaces.FinalizeSetns(config, userArgs); err != nil {
+		log.Fatalf("docker-exec: failed to exec: %s", err)
+	}
+}
+
+// TODO(vishh): Add support for running in priviledged mode and running as a different user.
+func (d *driver) Exec(c *execdriver.Command, processConfig *execdriver.ProcessConfig, pipes *execdriver.Pipes, startCallback execdriver.StartCallback) (int, error) {
+	active := d.activeContainers[c.ID]
+	if active == nil {
+		return -1, fmt.Errorf("No active container exists with ID %s", c.ID)
+	}
+	state, err := libcontainer.GetState(filepath.Join(d.root, c.ID))
+	if err != nil {
+		return -1, fmt.Errorf("State unavailable for container with ID %s. The container may have been cleaned up already. Error: %s", c.ID, err)
+	}
+
+	var term execdriver.Terminal
+
+	if processConfig.Tty {
+		term, err = NewTtyConsole(processConfig, pipes)
+	} else {
+		term, err = execdriver.NewStdConsole(processConfig, pipes)
+	}
+
+	processConfig.Terminal = term
+
+	args := append([]string{processConfig.Entrypoint}, processConfig.Arguments...)
+
+	return namespaces.ExecIn(active.container, state, args, os.Args[0], "exec", processConfig.Stdin, processConfig.Stdout, processConfig.Stderr, processConfig.Console,
+		func(cmd *exec.Cmd) {
+			if startCallback != nil {
+				startCallback(&c.ProcessConfig, cmd.Process.Pid)
+			}
+		})
+}

daemon/execdriver/native/utils.go

@@ -0,0 +1,35 @@
+// +build linux
+
+package native
+
+import (
+	"os"
+
+	"github.com/docker/libcontainer"
+	"github.com/docker/libcontainer/syncpipe"
+)
+
+func findUserArgs() []string {
+	for i, a := range os.Args {
+		if a == "--" {
+			return os.Args[i+1:]
+		}
+	}
+	return []string{}
+}
+
+// loadConfigFromFd loads a container's config from the sync pipe that is provided by
+// fd 3 when running a process
+func loadConfigFromFd() (*libcontainer.Config, error) {
+	syncPipe, err := syncpipe.NewSyncPipeFromFd(0, 3)
+	if err != nil {
+		return nil, err
+	}
+
+	var config *libcontainer.Config
+	if err := syncPipe.ReadFromParent(&config); err != nil {
+		return nil, err
+	}
+
+	return config, nil
+}

daemon/resize.go

@@ -19,6 +19,7 @@ func (daemon *Daemon) ContainerResize(job *engine.Job) engine.Status {
 	if err != nil {
 		return job.Error(err)
 	}
+
 	if container := daemon.Get(name); container != nil {
 		if err := container.Resize(height, width); err != nil {
 			return job.Error(err)
@@ -27,3 +28,26 @@ func (daemon *Daemon) ContainerResize(job *engine.Job) engine.Status {
 	}
 	return job.Errorf("No such container: %s", name)
 }
+
+func (daemon *Daemon) ContainerExecResize(job *engine.Job) engine.Status {
+	if len(job.Args) != 3 {
+		return job.Errorf("Not enough arguments. Usage: %s EXEC HEIGHT WIDTH\n", job.Name)
+	}
+	name := job.Args[0]
+	height, err := strconv.Atoi(job.Args[1])
+	if err != nil {
+		return job.Error(err)
+	}
+	width, err := strconv.Atoi(job.Args[2])
+	if err != nil {
+		return job.Error(err)
+	}
+	execConfig, err := daemon.getExecConfig(name)
+	if err != nil {
+		return job.Error(err)
+	}
+	if err := execConfig.Resize(height, width); err != nil {
+		return job.Error(err)
+	}
+	return engine.StatusOK
+}

docs/man/docker-exec.md

@@ -0,0 +1,29 @@
+% DOCKER(1) Docker User Manuals
+% Docker Community
+% SEPT 2014
+# NAME
+docker-exec - Run a command in an existing container
+
+# SYNOPSIS
+**docker exec**
+[**-d**|**--detach**[=*false*]]
+[**-i**|**--interactive**[=*false*]]
+[**-t**|**--tty**[=*false*]]
+ CONTAINER COMMAND [ARG...]
+
+# DESCRIPTION
+
+Run a process in an existing container. The existing CONTAINER needs to be active.
+
+# Options
+
+**-d**, **--detach**=*true*|*false*
+   Detached mode. This runs the new process in the background.
+
+**-i**, **--interactive**=*true*|*false*
+   When set to true, keep STDIN open even if not attached. The default is false.
+
+**-t**, **--tty**=*true*|*false*
+   When set to true Docker can allocate a pseudo-tty and attach to the standard
+input of the process. This can be used, for example, to run a throwaway
+interactive shell. The default value is false.

docs/sources/reference/commandline/cli.md

@@ -1295,6 +1295,35 @@ It is even useful to cherry-pick particular tags of an image repository
 
    $ sudo docker save -o ubuntu.tar ubuntu:lucid ubuntu:saucy
 
+## exec
+
+    Usage: docker exec CONTAINER COMMAND [ARG...]
+
+    Run a command in an existing container
+
+      -d, --detach=false         Detached mode: run the process in the background and exit
+      -i, --interactive=false    Keep STDIN open even if not attached
+      -t, --tty=false            Allocate a pseudo-TTY
+
+The `docker exec` command runs a user specified command as a new process in an existing
+user specified container. The container needs to be active.
+
+The `docker exec` command will typically be used after `docker run`.
+
+### Examples:
+
+    $ sudo docker run --name ubuntu_bash --rm -i -t ubuntu bash
+
+This will create a container named 'ubuntu_bash' and start a bash session.
+
+    $ sudo docker exec -d ubuntu_bash touch /tmp/execWorks
+
+This will create a new file '/tmp/execWorks' inside the existing and active container
+'ubuntu_bash', in the background.
+
+    $ sudo docker exec ubuntu_bash -it bash
+
+This will create a new bash session in the container 'ubuntu_bash'.
 
 ## search
 

engine/engine.go

@@ -122,6 +122,7 @@ func (eng *Engine) Job(name string, args ...string) *Job {
 		Stdout:  NewOutput(),
 		Stderr:  NewOutput(),
 		env:     &Env{},
+		closeIO: true,
 	}
 	if eng.Logging {
 		job.Stderr.Add(ioutils.NopWriteCloser(eng.Stderr))

engine/job.go

@@ -31,6 +31,7 @@ type Job struct {
 	handler Handler
 	status  Status
 	end     time.Time
+	closeIO bool
 }
 
 type Status int
@@ -78,6 +79,7 @@ func (job *Job) Run() error {
 		job.status = job.handler(job)
 		job.end = time.Now()
 	}
+	if job.closeIO {
 		// Wait for all background tasks to complete
 		if err := job.Stdout.Close(); err != nil {
 			return err
@@ -88,9 +90,11 @@ func (job *Job) Run() error {
 		if err := job.Stdin.Close(); err != nil {
 			return err
 		}
+	}
 	if job.status != 0 {
 		return fmt.Errorf("%s", Tail(errorMessage, 1))
 	}
+
 	return nil
 }
 
@@ -228,3 +232,7 @@ func (job *Job) Error(err error) Status {
 func (job *Job) StatusCode() int {
 	return int(job.status)
 }
+
+func (job *Job) SetCloseIO(val bool) {
+	job.closeIO = val
+}

integration-cli/docker_cli_run_test.go

@@ -1994,3 +1994,78 @@ func TestRunPortInUse(t *testing.T) {
 	deleteAllContainers()
 	logDone("run - fail if port already in use")
 }
+
+// "test" should be printed by docker exec
+func TestDockerExec(t *testing.T) {
+	runCmd := exec.Command(dockerBinary, "run", "-d", "--name", "testing", "busybox", "sh", "-c", "echo test > /tmp/file && sleep 100")
+	out, _, _, err := runCommandWithStdoutStderr(runCmd)
+	errorOut(err, t, out)
+
+	execCmd := exec.Command(dockerBinary, "exec", "testing", "cat", "/tmp/file")
+
+	out, _, err = runCommandWithOutput(execCmd)
+	errorOut(err, t, out)
+
+	out = strings.Trim(out, "\r\n")
+
+	if expected := "test"; out != expected {
+		t.Errorf("container exec should've printed %q but printed %q", expected, out)
+	}
+
+	deleteAllContainers()
+
+	logDone("exec - basic test")
+}
+
+// "test" should be printed by docker exec
+func TestDockerExecInteractive(t *testing.T) {
+	runCmd := exec.Command(dockerBinary, "run", "-d", "--name", "testing", "busybox", "sh", "-c", "echo test > /tmp/file && sleep 100")
+	out, _, _, err := runCommandWithStdoutStderr(runCmd)
+	errorOut(err, t, out)
+
+	execCmd := exec.Command(dockerBinary, "exec", "-i", "testing", "sh")
+	stdin, err := execCmd.StdinPipe()
+	if err != nil {
+		t.Fatal(err)
+	}
+	stdout, err := execCmd.StdoutPipe()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if err := execCmd.Start(); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := stdin.Write([]byte("cat /tmp/file\n")); err != nil {
+		t.Fatal(err)
+	}
+
+	r := bufio.NewReader(stdout)
+	line, err := r.ReadString('\n')
+	if err != nil {
+		t.Fatal(err)
+	}
+	line = strings.TrimSpace(line)
+	if line != "test" {
+		t.Fatalf("Output should be 'test', got '%q'", line)
+	}
+	if err := stdin.Close(); err != nil {
+		t.Fatal(err)
+	}
+	finish := make(chan struct{})
+	go func() {
+		if err := execCmd.Wait(); err != nil {
+			t.Fatal(err)
+		}
+		close(finish)
+	}()
+	select {
+	case <-finish:
+	case <-time.After(1 * time.Second):
+		t.Fatal("docker exec failed to exit on stdin close")
+	}
+
+	deleteAllContainers()
+
+	logDone("exec - Interactive test")
+}

runconfig/exec.go

@@ -0,0 +1,75 @@
+package runconfig
+
+import (
+	"github.com/docker/docker/engine"
+	flag "github.com/docker/docker/pkg/mflag"
+)
+
+type ExecConfig struct {
+	User         string
+	Privileged   bool
+	Tty          bool
+	Container    string
+	AttachStdin  bool
+	AttachStderr bool
+	AttachStdout bool
+	Detach       bool
+	Cmd          []string
+}
+
+func ExecConfigFromJob(job *engine.Job) *ExecConfig {
+	execConfig := &ExecConfig{
+		User:         job.Getenv("User"),
+		Privileged:   job.GetenvBool("Privileged"),
+		Tty:          job.GetenvBool("Tty"),
+		Container:    job.Getenv("Container"),
+		AttachStdin:  job.GetenvBool("AttachStdin"),
+		AttachStderr: job.GetenvBool("AttachStderr"),
+		AttachStdout: job.GetenvBool("AttachStdout"),
+	}
+	if cmd := job.GetenvList("Cmd"); cmd != nil {
+		execConfig.Cmd = cmd
+	}
+
+	return execConfig
+}
+
+func ParseExec(cmd *flag.FlagSet, args []string) (*ExecConfig, error) {
+	var (
+		flStdin   = cmd.Bool([]string{"i", "-interactive"}, false, "Keep STDIN open even if not attached")
+		flTty     = cmd.Bool([]string{"t", "-tty"}, false, "Allocate a pseudo-TTY")
+		flDetach  = cmd.Bool([]string{"d", "-detach"}, false, "Detached mode: run command in the background")
+		execCmd   []string
+		container string
+	)
+	if err := cmd.Parse(args); err != nil {
+		return nil, err
+	}
+	parsedArgs := cmd.Args()
+	if len(parsedArgs) > 1 {
+		container = cmd.Arg(0)
+		execCmd = parsedArgs[1:]
+	}
+
+	execConfig := &ExecConfig{
+		// TODO(vishh): Expose '-u' flag once it is supported.
+		User: "",
+		// TODO(vishh): Expose '-p' flag once it is supported.
+		Privileged: false,
+		Tty:        *flTty,
+		Cmd:        execCmd,
+		Container:  container,
+		Detach:     *flDetach,
+	}
+
+	// If -d is not set, attach to everything by default
+	if !*flDetach {
+		execConfig.AttachStdout = true
+		execConfig.AttachStderr = true
+		if *flStdin {
+			execConfig.AttachStdin = true
+		}
+	}
+
+	return execConfig, nil
+}