pkg/package: remove promise package

The promise package represents a simple enough concurrency pattern that
replicating it in place is sufficient. To end the propagation of this
package, it has been removed and the uses have been inlined.

While this code could likely be refactored to be simpler without the
package, the changes have been minimized to reduce the possibility of
defects. Someone else may want to do further refactoring to remove
closures and reduce the number of goroutines in use.

Signed-off-by: Stephen J Day <stephen.day@docker.com>

container/stream/attach.go

@@ -7,7 +7,6 @@ import (
 	"golang.org/x/net/context"
 
 	"github.com/docker/docker/pkg/pools"
-	"github.com/docker/docker/pkg/promise"
 	"github.com/docker/docker/pkg/term"
 	"github.com/sirupsen/logrus"
 )
@@ -58,7 +57,7 @@ func (c *Config) AttachStreams(cfg *AttachConfig) {
 }
 
 // CopyStreams starts goroutines to copy data in and out to/from the container
-func (c *Config) CopyStreams(ctx context.Context, cfg *AttachConfig) chan error {
+func (c *Config) CopyStreams(ctx context.Context, cfg *AttachConfig) <-chan error {
 	var (
 		wg     sync.WaitGroup
 		errors = make(chan error, 3)
@@ -137,35 +136,42 @@ func (c *Config) CopyStreams(ctx context.Context, cfg *AttachConfig) chan error
 	go attachStream("stdout", cfg.Stdout, cfg.CStdout)
 	go attachStream("stderr", cfg.Stderr, cfg.CStderr)
 
-	return promise.Go(func() error {
-		done := make(chan struct{})
-		go func() {
-			wg.Wait()
-			close(done)
-		}()
-		select {
-		case <-done:
-		case <-ctx.Done():
-			// close all pipes
-			if cfg.CStdin != nil {
-				cfg.CStdin.Close()
-			}
-			if cfg.CStdout != nil {
-				cfg.CStdout.Close()
-			}
-			if cfg.CStderr != nil {
-				cfg.CStderr.Close()
+	errs := make(chan error, 1)
+
+	go func() {
+		defer close(errs)
+		errs <- func() error {
+			done := make(chan struct{})
+			go func() {
+				wg.Wait()
+				close(done)
+			}()
+			select {
+			case <-done:
+			case <-ctx.Done():
+				// close all pipes
+				if cfg.CStdin != nil {
+					cfg.CStdin.Close()
+				}
+				if cfg.CStdout != nil {
+					cfg.CStdout.Close()
+				}
+				if cfg.CStderr != nil {
+					cfg.CStderr.Close()
+				}
+				<-done
 			}
-			<-done
-		}
-		close(errors)
-		for err := range errors {
-			if err != nil {
-				return err
+			close(errors)
+			for err := range errors {
+				if err != nil {
+					return err
+				}
 			}
-		}
-		return nil
-	})
+			return nil
+		}()
+	}()
+
+	return errs
 }
 
 func copyEscapable(dst io.Writer, src io.ReadCloser, keys []byte) (written int64, err error) {

pkg/archive/archive.go

@@ -20,7 +20,6 @@ import (
 	"github.com/docker/docker/pkg/idtools"
 	"github.com/docker/docker/pkg/ioutils"
 	"github.com/docker/docker/pkg/pools"
-	"github.com/docker/docker/pkg/promise"
 	"github.com/docker/docker/pkg/system"
 	"github.com/sirupsen/logrus"
 )
@@ -1095,36 +1094,42 @@ func (archiver *Archiver) CopyFileWithTar(src, dst string) (err error) {
 	}
 
 	r, w := io.Pipe()
-	errC := promise.Go(func() error {
-		defer w.Close()
+	errC := make(chan error, 1)
 
-		srcF, err := os.Open(src)
-		if err != nil {
-			return err
-		}
-		defer srcF.Close()
+	go func() {
+		defer close(errC)
 
-		hdr, err := tar.FileInfoHeader(srcSt, "")
-		if err != nil {
-			return err
-		}
-		hdr.Name = filepath.Base(dst)
-		hdr.Mode = int64(chmodTarEntry(os.FileMode(hdr.Mode)))
+		errC <- func() error {
+			defer w.Close()
 
-		if err := remapIDs(archiver.IDMappingsVar, hdr); err != nil {
-			return err
-		}
+			srcF, err := os.Open(src)
+			if err != nil {
+				return err
+			}
+			defer srcF.Close()
 
-		tw := tar.NewWriter(w)
-		defer tw.Close()
-		if err := tw.WriteHeader(hdr); err != nil {
-			return err
-		}
-		if _, err := io.Copy(tw, srcF); err != nil {
-			return err
-		}
-		return nil
-	})
+			hdr, err := tar.FileInfoHeader(srcSt, "")
+			if err != nil {
+				return err
+			}
+			hdr.Name = filepath.Base(dst)
+			hdr.Mode = int64(chmodTarEntry(os.FileMode(hdr.Mode)))
+
+			if err := remapIDs(archiver.IDMappingsVar, hdr); err != nil {
+				return err
+			}
+
+			tw := tar.NewWriter(w)
+			defer tw.Close()
+			if err := tw.WriteHeader(hdr); err != nil {
+				return err
+			}
+			if _, err := io.Copy(tw, srcF); err != nil {
+				return err
+			}
+			return nil
+		}()
+	}()
 	defer func() {
 		if er := <-errC; err == nil && er != nil {
 			err = er

pkg/containerfs/archiver.go

@@ -9,7 +9,6 @@ import (
 
 	"github.com/docker/docker/pkg/archive"
 	"github.com/docker/docker/pkg/idtools"
-	"github.com/docker/docker/pkg/promise"
 	"github.com/docker/docker/pkg/system"
 	"github.com/sirupsen/logrus"
 )
@@ -122,40 +121,45 @@ func (archiver *Archiver) CopyFileWithTar(src, dst string) (err error) {
 	}
 
 	r, w := io.Pipe()
-	errC := promise.Go(func() error {
-		defer w.Close()
-
-		srcF, err := srcDriver.Open(src)
-		if err != nil {
-			return err
-		}
-		defer srcF.Close()
-
-		hdr, err := tar.FileInfoHeader(srcSt, "")
-		if err != nil {
-			return err
-		}
-		hdr.Name = dstDriver.Base(dst)
-		if dstDriver.OS() == "windows" {
-			hdr.Mode = int64(chmodTarEntry(os.FileMode(hdr.Mode)))
-		} else {
-			hdr.Mode = int64(os.FileMode(hdr.Mode))
-		}
-
-		if err := remapIDs(archiver.IDMappingsVar, hdr); err != nil {
-			return err
-		}
-
-		tw := tar.NewWriter(w)
-		defer tw.Close()
-		if err := tw.WriteHeader(hdr); err != nil {
-			return err
-		}
-		if _, err := io.Copy(tw, srcF); err != nil {
-			return err
-		}
-		return nil
-	})
+	errC := make(chan error, 1)
+
+	go func() {
+		defer close(errC)
+		errC <- func() error {
+			defer w.Close()
+
+			srcF, err := srcDriver.Open(src)
+			if err != nil {
+				return err
+			}
+			defer srcF.Close()
+
+			hdr, err := tar.FileInfoHeader(srcSt, "")
+			if err != nil {
+				return err
+			}
+			hdr.Name = dstDriver.Base(dst)
+			if dstDriver.OS() == "windows" {
+				hdr.Mode = int64(chmodTarEntry(os.FileMode(hdr.Mode)))
+			} else {
+				hdr.Mode = int64(os.FileMode(hdr.Mode))
+			}
+
+			if err := remapIDs(archiver.IDMappingsVar, hdr); err != nil {
+				return err
+			}
+
+			tw := tar.NewWriter(w)
+			defer tw.Close()
+			if err := tw.WriteHeader(hdr); err != nil {
+				return err
+			}
+			if _, err := io.Copy(tw, srcF); err != nil {
+				return err
+			}
+			return nil
+		}()
+	}()
 	defer func() {
 		if er := <-errC; err == nil && er != nil {
 			err = er

pkg/promise/promise.go

@@ -1,11 +0,0 @@
-package promise
-
-// Go is a basic promise implementation: it wraps calls a function in a goroutine,
-// and returns a channel which will later return the function's return value.
-func Go(f func() error) chan error {
-	ch := make(chan error, 1)
-	go func() {
-		ch <- f()
-	}()
-	return ch
-}

pkg/promise/promise_test.go

@@ -1,25 +0,0 @@
-package promise
-
-import (
-	"errors"
-	"testing"
-
-	"github.com/stretchr/testify/require"
-)
-
-func TestGo(t *testing.T) {
-	errCh := Go(functionWithError)
-	er := <-errCh
-	require.EqualValues(t, "Error Occurred", er.Error())
-
-	noErrCh := Go(functionWithNoError)
-	er = <-noErrCh
-	require.Nil(t, er)
-}
-
-func functionWithError() (err error) {
-	return errors.New("Error Occurred")
-}
-func functionWithNoError() (err error) {
-	return nil
-}