remove unnecessary gateway container interface

Signed-off-by: Cory Bennett <cbennett@netflix.com>

frontend/gateway/container.go

@@ -18,13 +18,6 @@ import (
 	"golang.org/x/sync/errgroup"
 )
 
-type Container interface {
-	client.Container
-	// OnRelease allows callbacks to free up resources when the container exits.
-	// The functions are called in LIFO order.
-	OnRelease(func() error)
-}
-
 type NewContainerRequest struct {
 	ContainerID  string
 	NetMode      opspb.NetMode
@@ -43,7 +36,7 @@ type Mount struct {
 	RefProxy  solver.ResultProxy
 }
 
-func NewContainer(ctx context.Context, e executor.Executor, req NewContainerRequest) (Container, error) {
+func NewContainer(ctx context.Context, e executor.Executor, req NewContainerRequest) (client.Container, error) {
 	ctx, cancel := context.WithCancel(ctx)
 	eg, ctx := errgroup.WithContext(ctx)
 	ctr := &gatewayContainer{
@@ -77,9 +70,10 @@ func NewContainer(ctx context.Context, e executor.Executor, req NewContainerRequ
 			if err != nil {
 				return nil, stack.Enable(err)
 			}
-			ctr.OnRelease(func() error {
+			ctr.cleanup = append(ctr.cleanup, func() error {
 				return stack.Enable(ref.Release(context.TODO()))
 			})
+
 			execMount.Src = ref
 		}
 
@@ -186,12 +180,6 @@ func (gwCtr *gatewayContainer) Release(ctx context.Context) error {
 	return stack.Enable(err2)
 }
 
-// OnRelease will call the provided function when the Container has been
-// released.  The functions are called in LIFO order.
-func (gwCtr *gatewayContainer) OnRelease(f func() error) {
-	gwCtr.cleanup = append(gwCtr.cleanup, f)
-}
-
 type gatewayContainerProcess struct {
 	errGroup *errgroup.Group
 	groupCtx context.Context

frontend/gateway/gateway.go

@@ -322,7 +322,7 @@ func newBridgeForwarder(ctx context.Context, llbBridge frontend.FrontendLLBBridg
 		workers:   workers,
 		inputs:    inputs,
 		sid:       sid,
-		ctrs:      map[string]Container{},
+		ctrs:      map[string]gwclient.Container{},
 	}
 	return lbf
 }
@@ -423,7 +423,7 @@ type llbBridgeForwarder struct {
 	isErrServerClosed bool
 	sid               string
 	*pipe
-	ctrs   map[string]Container
+	ctrs   map[string]gwclient.Container
 	ctrsMu sync.Mutex
 }
 
@@ -1031,12 +1031,6 @@ func (lbf *llbBridgeForwarder) ExecProcess(srv pb.LLBBridge_ExecProcessServer) e
 				}
 				pio.resize = proc.Resize
 
-				// ensure process has been canceled if the container is released
-				ctr.OnRelease(func() error {
-					initCancel()
-					return nil
-				})
-
 				eg.Go(func() error {
 					<-pio.done
 					logrus.Debugf("|---> Done Message %s", pid)