worker: add stdout/stderr to runc worker

Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>

control/control_test.go

@@ -3,6 +3,7 @@
 package control
 
 import (
+	"bytes"
 	"context"
 	"io"
 	"io/ioutil"
@@ -107,21 +108,23 @@ func TestControl(t *testing.T) {
 
 	meta := worker.Meta{
 		Args: []string{"/bin/sh", "-c", "echo \"foo\" > /bar"},
-		// Args: []string{"/bin/sleep", "3"},
 		Cwd:  "/",
 	}
 
 	m := make(map[string]cache.Mountable)
 	m["/"] = snap
 
-	err = w.Exec(context.TODO(), meta, m)
+	stderr := bytes.NewBuffer(nil)
+
+	err = w.Exec(context.TODO(), meta, m, nil, &nopCloser{stderr})
 	assert.Error(t, err) // Read-only root
+	assert.Contains(t, stderr.String(), "Read-only file system")
 
 	root, err := cm.New(snap)
 	assert.NoError(t, err)
 
 	m["/"] = root
-	err = w.Exec(context.TODO(), meta, m)
+	err = w.Exec(context.TODO(), meta, m, nil, nil)
 	assert.NoError(t, err)
 
 	rf, err := root.Freeze()
@@ -241,3 +244,11 @@ func (rc *readCounter) Read(p []byte) (n int, err error) {
 	rc.c += int64(n)
 	return
 }
+
+type nopCloser struct {
+	io.Writer
+}
+
+func (n *nopCloser) Close() error {
+	return nil
+}

worker/runcworker/worker.go

@@ -4,7 +4,9 @@ import (
 	"crypto/rand"
 	"encoding/hex"
 	"encoding/json"
+	"io"
 	"os"
+	"os/exec"
 	"path/filepath"
 	"syscall"
 
@@ -36,7 +38,7 @@ func New(root string) (worker.Worker, error) {
 	return w, nil
 }
 
-func (w *runcworker) Exec(ctx context.Context, meta worker.Meta, mounts map[string]cache.Mountable) error {
+func (w *runcworker) Exec(ctx context.Context, meta worker.Meta, mounts map[string]cache.Mountable, stdout, stderr io.WriteCloser) error {
 	root, ok := mounts["/"]
 	if !ok {
 		return errors.Errorf("no root mount")
@@ -81,12 +83,8 @@ func (w *runcworker) Exec(ctx context.Context, meta worker.Meta, mounts map[stri
 		return err
 	}
 
-	io, err := runc.NewSTDIO()
-	if err != nil {
-		return err
-	}
 	status, err := w.runc.Run(ctx, id, bundle, &runc.CreateOpts{
-		IO: io,
+		IO: &forwardIO{stdout: stdout, stderr: stderr},
 	})
 	if status != 0 {
 		return errors.Errorf("exit code %d", status)
@@ -95,6 +93,31 @@ func (w *runcworker) Exec(ctx context.Context, meta worker.Meta, mounts map[stri
 	return err
 }
 
+type forwardIO struct {
+	stdout, stderr io.WriteCloser
+}
+
+func (s *forwardIO) Close() error {
+	return nil
+}
+
+func (s *forwardIO) Set(cmd *exec.Cmd) {
+	cmd.Stdout = s.stdout
+	cmd.Stderr = s.stderr
+}
+
+func (s *forwardIO) Stdin() io.WriteCloser {
+	return nil
+}
+
+func (s *forwardIO) Stdout() io.ReadCloser {
+	return nil
+}
+
+func (s *forwardIO) Stderr() io.ReadCloser {
+	return nil
+}
+
 func generateID() string {
 	b := make([]byte, 32)
 	if _, err := rand.Read(b); err != nil {

worker/worker.go

@@ -1,6 +1,8 @@
 package worker
 
 import (
+	"io"
+
 	"github.com/tonistiigi/buildkit_poc/cache"
 	"golang.org/x/net/context"
 )
@@ -16,5 +18,5 @@ type Meta struct {
 
 type Worker interface {
 	// TODO: add stdout/err
-	Exec(ctx context.Context, meta Meta, mounts map[string]cache.Mountable) error
+	Exec(ctx context.Context, meta Meta, mounts map[string]cache.Mountable, stdout, stderr io.WriteCloser) error
 }