rpc: add Closing method

api/api_common.go

@@ -38,6 +38,8 @@ type Common interface {
 
 	// trigger graceful shutdown
 	Shutdown(context.Context) error
+
+	Closing(context.Context) (<-chan struct{}, error)
 }
 
 // Version provides various build-time information

api/apistruct/struct.go

@@ -50,7 +50,8 @@ type CommonStruct struct {
 		LogList     func(context.Context) ([]string, error)     `perm:"write"`
 		LogSetLevel func(context.Context, string, string) error `perm:"write"`
 
-		Shutdown func(context.Context) error `perm:"admin"`
+		Shutdown func(context.Context) error                    `perm:"admin"`
+		Closing  func(context.Context) (<-chan struct{}, error) `perm:"read"`
 	}
 }
 
@@ -313,6 +314,10 @@ func (c *CommonStruct) Shutdown(ctx context.Context) error {
 	return c.Internal.Shutdown(ctx)
 }
 
+func (c *CommonStruct) Closing(ctx context.Context) (<-chan struct{}, error) {
+	return c.Internal.Closing(ctx)
+}
+
 // FullNodeStruct
 
 func (c *FullNodeStruct) ClientListImports(ctx context.Context) ([]api.Import, error) {

node/impl/common/common.go

@@ -139,4 +139,8 @@ func (a *CommonAPI) Shutdown(ctx context.Context) error {
 	return nil
 }
 
+func (a *CommonAPI) Closing(ctx context.Context) (<-chan struct{}, error) {
+	return make(chan struct{}), nil // relies on jsonrpc closing
+}
+
 var _ api.Common = &CommonAPI{}