client: Client.ImageLoad: close reader on context cancellation

Use a cancelReadCloser to automatically close the reader when the context
is cancelled. Consumers are still recommended to manually close the reader,
but the cancelReadCloser makes the Close idempotent.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

client/image_load.go

@@ -15,6 +15,8 @@ type ImageLoadResult interface {
 
 // ImageLoad loads an image in the docker host from the client host. It's up
 // to the caller to close the [ImageLoadResult] returned by this function.
+//
+// The underlying [io.ReadCloser] is automatically closed if the context is canceled,
 func (cli *Client) ImageLoad(ctx context.Context, input io.Reader, loadOpts ...ImageLoadOption) (ImageLoadResult, error) {
 	var opts imageLoadOpts
 	for _, opt := range loadOpts {
@@ -47,31 +49,16 @@ func (cli *Client) ImageLoad(ctx context.Context, input io.Reader, loadOpts ...I
 		return nil, err
 	}
 	return &imageLoadResult{
-		body: resp.Body,
+		ReadCloser: newCancelReadCloser(ctx, resp.Body),
 	}, nil
 }
 
 // imageLoadResult returns information to the client about a load process.
 type imageLoadResult struct {
-	// body must be closed to avoid a resource leak
+	io.ReadCloser
-	body io.ReadCloser
 }
 
 var (
 	_ io.ReadCloser   = (*imageLoadResult)(nil)
 	_ ImageLoadResult = (*imageLoadResult)(nil)
 )
-
-func (r *imageLoadResult) Read(p []byte) (int, error) {
-	if r == nil || r.body == nil {
-		return 0, io.EOF
-	}
-	return r.body.Read(p)
-}
-
-func (r *imageLoadResult) Close() error {
-	if r == nil || r.body == nil {
-		return nil
-	}
-	return r.body.Close()
-}

integration/build/build_userns_linux_test.go

@@ -106,8 +106,8 @@ func TestBuildUserNamespaceValidateCapabilitiesAreV2(t *testing.T) {
 	loadResp, err := clientNoUserRemap.ImageLoad(ctx, tarReader)
 	assert.NilError(t, err, "failed to load image tar file")
 	defer loadResp.Close()
-	buf = bytes.NewBuffer(nil)
+	var buf2 bytes.Buffer
-	err = jsonmessage.DisplayJSONMessagesStream(loadResp, buf, 0, false, nil)
+	err = jsonmessage.DisplayJSONMessagesStream(loadResp, &buf2, 0, false, nil)
 	assert.NilError(t, err)
 
 	cid := container.Run(ctx, t, clientNoUserRemap,

integration/daemon/migration_test.go

@@ -146,10 +146,10 @@ func TestMigrateSaveLoad(t *testing.T) {
 	assert.Equal(t, info.Images, 0)
 
 	// Import
-	lr, err := apiClient.ImageLoad(ctx, bytes.NewReader(buf.Bytes()), client.ImageLoadWithQuiet(true))
+	resp, err := apiClient.ImageLoad(ctx, bytes.NewReader(buf.Bytes()), client.ImageLoadWithQuiet(true))
 	assert.NilError(t, err)
-	io.Copy(io.Discard, lr)
+	_, _ = io.Copy(io.Discard, resp)
-	lr.Close()
+	_ = resp.Close()
 
 	result := container.RunAttach(ctx, t, apiClient, func(c *container.TestContainerConfig) {
 		c.Name = "Migration-save-load-" + snapshotter

integration/image/save_test.go

@@ -343,11 +343,9 @@ func TestSaveAndLoadPlatform(t *testing.T) {
 			// load the full exported image (all platforms in it)
 			resp, err := apiClient.ImageLoad(ctx, rdr)
 			assert.NilError(t, err)
-			_, err = io.ReadAll(resp)
+			_, _ = io.Copy(io.Discard, resp)
-			resp.Close()
+			_ = resp.Close()
-			assert.NilError(t, err)
+			_ = rdr.Close()
-
-			rdr.Close()
 
 			// verify the loaded image has all the expected platforms
 			for _, p := range tc.expectedSavedPlatforms {
@@ -381,11 +379,9 @@ func TestSaveAndLoadPlatform(t *testing.T) {
 			// load the exported image on the specified platforms only
 			resp, err = apiClient.ImageLoad(ctx, rdr, client.ImageLoadWithPlatforms(tc.loadPlatforms...))
 			assert.NilError(t, err)
-			_, err = io.ReadAll(resp)
+			_, _ = io.Copy(io.Discard, resp)
-			resp.Close()
+			_ = resp.Close()
-			assert.NilError(t, err)
+			_ = rdr.Close()
-
-			rdr.Close()
 
 			// verify the image was loaded for the specified platforms
 			for _, p := range tc.expectedLoadedPlatforms {

integration/internal/image/load.go

@@ -30,7 +30,7 @@ func Load(ctx context.Context, t *testing.T, apiClient client.APIClient, imageFu
 	resp, err := apiClient.ImageLoad(ctx, rc, client.ImageLoadWithQuiet(true))
 	assert.NilError(t, err, "Failed to load dangling image")
 
-	defer resp.Close()
+	defer func() { _ = resp.Close() }()
 
 	if !assert.Check(t, err) {
 		respBody, err := io.ReadAll(resp)

integration/plugin/authz/authz_plugin_test.go

@@ -445,11 +445,12 @@ func imageLoad(ctx context.Context, apiClient client.APIClient, path string) err
 		return err
 	}
 	defer file.Close()
-	response, err := apiClient.ImageLoad(ctx, file, client.ImageLoadWithQuiet(true))
+	resp, err := apiClient.ImageLoad(ctx, file, client.ImageLoadWithQuiet(true))
 	if err != nil {
 		return err
 	}
-	defer response.Close()
+	_, _ = io.Copy(io.Discard, resp)
+	_ = resp.Close()
 	return nil
 }
 

internal/testutil/daemon/daemon.go

@@ -886,7 +886,8 @@ func (d *Daemon) LoadImage(ctx context.Context, t testing.TB, img string) {
 
 	resp, err := c.ImageLoad(ctx, reader, client.ImageLoadWithQuiet(true))
 	assert.NilError(t, err, "[%s] failed to load %s", d.id, img)
-	defer resp.Close()
+	_, _ = io.Copy(io.Discard, resp)
+	_ = resp.Close()
 }
 
 func (d *Daemon) getClientConfig() (*clientConfig, error) {

vendor/github.com/moby/moby/client/image_load.go

@@ -15,6 +15,8 @@ type ImageLoadResult interface {
 
 // ImageLoad loads an image in the docker host from the client host. It's up
 // to the caller to close the [ImageLoadResult] returned by this function.
+//
+// The underlying [io.ReadCloser] is automatically closed if the context is canceled,
 func (cli *Client) ImageLoad(ctx context.Context, input io.Reader, loadOpts ...ImageLoadOption) (ImageLoadResult, error) {
 	var opts imageLoadOpts
 	for _, opt := range loadOpts {
@@ -47,31 +49,16 @@ func (cli *Client) ImageLoad(ctx context.Context, input io.Reader, loadOpts ...I
 		return nil, err
 	}
 	return &imageLoadResult{
-		body: resp.Body,
+		ReadCloser: newCancelReadCloser(ctx, resp.Body),
 	}, nil
 }
 
 // imageLoadResult returns information to the client about a load process.
 type imageLoadResult struct {
-	// body must be closed to avoid a resource leak
+	io.ReadCloser
-	body io.ReadCloser
 }
 
 var (
 	_ io.ReadCloser   = (*imageLoadResult)(nil)
 	_ ImageLoadResult = (*imageLoadResult)(nil)
 )
-
-func (r *imageLoadResult) Read(p []byte) (int, error) {
-	if r == nil || r.body == nil {
-		return 0, io.EOF
-	}
-	return r.body.Read(p)
-}
-
-func (r *imageLoadResult) Close() error {
-	if r == nil || r.body == nil {
-		return nil
-	}
-	return r.body.Close()
-}