Use a child context for errgroup in dispatch

dmcgowan · dmcgowan · commit c017e0efed64 · 2019-08-09T16:01:23.000-07:00
Prevent an errgroup error from causing the acquire to
return a cancellation error. Previously any error
from the errgroup would cause the Dispatch to always
return the cancelled error.

Signed-off-by: Derek McGowan &lt;derek@mcgstyle.net&gt;
diff --git a/images/handlers.go b/images/handlers.go
@@ -117,7 +117,7 @@ func Walk(ctx context.Context, handler Handler, descs ...ocispec.Descriptor) err
 //
 // If any handler returns an error, the dispatch session will be canceled.
 func Dispatch(ctx context.Context, handler Handler, limiter *semaphore.Weighted, descs ...ocispec.Descriptor) error {
-	eg, ctx := errgroup.WithContext(ctx)
+	eg, ctx2 := errgroup.WithContext(ctx)
 	for _, desc := range descs {
 		desc := desc
 
@@ -126,10 +126,11 @@ func Dispatch(ctx context.Context, handler Handler, limiter *semaphore.Weighted,
 				return err
 			}
 		}
+
 		eg.Go(func() error {
 			desc := desc
 
-			children, err := handler.Handle(ctx, desc)
+			children, err := handler.Handle(ctx2, desc)
 			if limiter != nil {
 				limiter.Release(1)
 			}
@@ -141,7 +142,7 @@ func Dispatch(ctx context.Context, handler Handler, limiter *semaphore.Weighted,
 			}
 
 			if len(children) > 0 {
-				return Dispatch(ctx, handler, limiter, children...)
+				return Dispatch(ctx2, handler, limiter, children...)
 			}
 
 			return nil

Original file line number	Diff line number	Diff line change
`@@ -117,7 +117,7 @@ func Walk(ctx context.Context, handler Handler, descs ...ocispec.Descriptor) err`
`117`	`117`	`//`
`118`	`118`	`// If any handler returns an error, the dispatch session will be canceled.`
`119`	`119`	`func Dispatch(ctx context.Context, handler Handler, limiter *semaphore.Weighted, descs ...ocispec.Descriptor) error {`
`120`		`- eg, ctx := errgroup.WithContext(ctx)`
	`120`	`+ eg, ctx2 := errgroup.WithContext(ctx)`
`121`	`121`	`for _, desc := range descs {`
`122`	`122`	`desc := desc`
`123`	`123`
`@@ -126,10 +126,11 @@ func Dispatch(ctx context.Context, handler Handler, limiter *semaphore.Weighted,`
`126`	`126`	`return err`
`127`	`127`	`}`
`128`	`128`	`}`
	`129`	`+`
`129`	`130`	`eg.Go(func() error {`
`130`	`131`	`desc := desc`
`131`	`132`
`132`		`- children, err := handler.Handle(ctx, desc)`
	`133`	`+ children, err := handler.Handle(ctx2, desc)`
`133`	`134`	`if limiter != nil {`
`134`	`135`	`limiter.Release(1)`
`135`	`136`	`}`
`@@ -141,7 +142,7 @@ func Dispatch(ctx context.Context, handler Handler, limiter *semaphore.Weighted,`
`141`	`142`	`}`
`142`	`143`
`143`	`144`	`if len(children) > 0 {`
`144`		`- return Dispatch(ctx, handler, limiter, children...)`
	`145`	`+ return Dispatch(ctx2, handler, limiter, children...)`
`145`	`146`	`}`
`146`	`147`
`147`	`148`	`return nil`