Add create/start to exec processes in shim

This splits up the create and start of an exec process in the shim to
have two separate steps like the initial process.  This will allow
better state reporting for individual process along with a more robust
wait for execs.

Signed-off-by: Michael Crosby <crosbymichael@gmail.com>

linux/shim/exec.go

@@ -36,6 +36,8 @@ type execProcess struct {
 	closers []io.Closer
 	stdin   io.Closer
 	stdio   stdio
+	path    string
+	spec    specs.Process
 
 	parent *initProcess
 }
@@ -44,43 +46,6 @@ func newExecProcess(context context.Context, path string, r *shimapi.ExecProcess
 	if err := identifiers.Validate(id); err != nil {
 		return nil, errors.Wrapf(err, "invalid exec id")
 	}
-
-	e := &execProcess{
-		id:     id,
-		parent: parent,
-		stdio: stdio{
-			stdin:    r.Stdin,
-			stdout:   r.Stdout,
-			stderr:   r.Stderr,
-			terminal: r.Terminal,
-		},
-	}
-	var (
-		err     error
-		socket  *runc.Socket
-		io      runc.IO
-		pidfile = filepath.Join(path, fmt.Sprintf("%s.pid", id))
-	)
-	if r.Terminal {
-		if socket, err = runc.NewConsoleSocket(filepath.Join(path, "pty.sock")); err != nil {
-			return nil, errors.Wrap(err, "failed to create runc console socket")
-		}
-		defer os.Remove(socket.Path())
-	} else {
-		// TODO: get uid/gid
-		if io, err = runc.NewPipeIO(0, 0); err != nil {
-			return nil, errors.Wrap(err, "failed to create runc io pipes")
-		}
-		e.io = io
-	}
-	opts := &runc.ExecOpts{
-		PidFile: pidfile,
-		IO:      io,
-		Detach:  true,
-	}
-	if socket != nil {
-		opts.ConsoleSocket = socket
-	}
 	// process exec request
 	var spec specs.Process
 	if err := json.Unmarshal(r.Spec.Value, &spec); err != nil {
@@ -88,39 +53,18 @@ func newExecProcess(context context.Context, path string, r *shimapi.ExecProcess
 	}
 	spec.Terminal = r.Terminal
 
-	if err := parent.runtime.Exec(context, parent.id, spec, opts); err != nil {
-		return nil, parent.runtimeError(err, "OCI runtime exec failed")
+	e := &execProcess{
+		id:     id,
+		path:   path,
+		parent: parent,
+		spec:   spec,
+		stdio: stdio{
+			stdin:    r.Stdin,
+			stdout:   r.Stdout,
+			stderr:   r.Stderr,
+			terminal: r.Terminal,
+		},
 	}
-	if r.Stdin != "" {
-		sc, err := fifo.OpenFifo(context, r.Stdin, syscall.O_WRONLY|syscall.O_NONBLOCK, 0)
-		if err != nil {
-			return nil, errors.Wrapf(err, "failed to open stdin fifo %s", r.Stdin)
-		}
-		e.closers = append(e.closers, sc)
-		e.stdin = sc
-	}
-	var copyWaitGroup sync.WaitGroup
-	if socket != nil {
-		console, err := socket.ReceiveMaster()
-		if err != nil {
-			return nil, errors.Wrap(err, "failed to retrieve console master")
-		}
-		console, err = e.parent.platform.copyConsole(context, console, r.Stdin, r.Stdout, r.Stderr, &e.WaitGroup, &copyWaitGroup)
-		if err != nil {
-			return nil, errors.Wrap(err, "failed to start console copy")
-		}
-		e.console = console
-	} else {
-		if err := copyPipes(context, io, r.Stdin, r.Stdout, r.Stderr, &e.WaitGroup, &copyWaitGroup); err != nil {
-			return nil, errors.Wrap(err, "failed to start io pipe copy")
-		}
-	}
-	copyWaitGroup.Wait()
-	pid, err := runc.ReadPidFile(opts.PidFile)
-	if err != nil {
-		return nil, errors.Wrap(err, "failed to retrieve OCI runtime exec pid")
-	}
-	e.pid = pid
 	return e, nil
 }
 
@@ -178,3 +122,63 @@ func (e *execProcess) Stdin() io.Closer {
 func (e *execProcess) Stdio() stdio {
 	return e.stdio
 }
+
+func (e *execProcess) Start(ctx context.Context) (err error) {
+	var (
+		socket  *runc.Socket
+		io      runc.IO
+		pidfile = filepath.Join(e.path, fmt.Sprintf("%s.pid", e.id))
+	)
+	if e.stdio.terminal {
+		if socket, err = runc.NewConsoleSocket(filepath.Join(e.path, "pty.sock")); err != nil {
+			return errors.Wrap(err, "failed to create runc console socket")
+		}
+		defer os.Remove(socket.Path())
+	} else {
+		if io, err = runc.NewPipeIO(0, 0); err != nil {
+			return errors.Wrap(err, "failed to create runc io pipes")
+		}
+		e.io = io
+	}
+	opts := &runc.ExecOpts{
+		PidFile: pidfile,
+		IO:      io,
+		Detach:  true,
+	}
+	if socket != nil {
+		opts.ConsoleSocket = socket
+	}
+	if err := e.parent.runtime.Exec(ctx, e.parent.id, e.spec, opts); err != nil {
+		return e.parent.runtimeError(err, "OCI runtime exec failed")
+	}
+	if e.stdio.stdin != "" {
+		sc, err := fifo.OpenFifo(ctx, e.stdio.stdin, syscall.O_WRONLY|syscall.O_NONBLOCK, 0)
+		if err != nil {
+			return errors.Wrapf(err, "failed to open stdin fifo %s", e.stdio.stdin)
+		}
+		e.closers = append(e.closers, sc)
+		e.stdin = sc
+	}
+	var copyWaitGroup sync.WaitGroup
+	if socket != nil {
+		console, err := socket.ReceiveMaster()
+		if err != nil {
+			return errors.Wrap(err, "failed to retrieve console master")
+		}
+		e.console = console
+		if err := e.parent.platform.copyConsole(ctx, console, e.stdio.stdin, e.stdio.stdout, e.stdio.stderr, &e.WaitGroup, &copyWaitGroup); err != nil {
+			return errors.Wrap(err, "failed to start console copy")
+		}
+	} else {
+		if err := copyPipes(ctx, io, e.stdio.stdin, e.stdio.stdout, e.stdio.stderr, &e.WaitGroup, &copyWaitGroup); err != nil {
+			return errors.Wrap(err, "failed to start io pipe copy")
+		}
+	}
+	copyWaitGroup.Wait()
+	pid, err := runc.ReadPidFile(opts.PidFile)
+	if err != nil {
+		return errors.Wrap(err, "failed to retrieve OCI runtime exec pid")
+	}
+	e.pid = pid
+	return nil
+}