When the server exits (^C or because docker/systemd exits it), streaming gRPC clients must be

closed. Currently, the server does not exit until the gRPC client disconnects.

internal/grpcapi/server.go

@@ -17,12 +17,15 @@ import (
 // Server implements the MaglevServer gRPC interface.
 type Server struct {
 	UnimplementedMaglevServer
+	ctx     context.Context
 	checker *checker.Checker
 }
 
-// NewServer creates a Server backed by the given Checker.
-func NewServer(c *checker.Checker) *Server {
-	return &Server{checker: c}
+// NewServer creates a Server backed by the given Checker. The provided context
+// controls the lifetime of streaming RPCs: cancelling it closes all active
+// WatchBackendEvents streams so that grpc.Server.GracefulStop can complete.
+func NewServer(ctx context.Context, c *checker.Checker) *Server {
+	return &Server{ctx: ctx, checker: c}
 }
 
 // ListFrontends returns the names of all configured frontends.
@@ -112,6 +115,8 @@ func (s *Server) WatchBackendEvents(_ *WatchRequest, stream Maglev_WatchBackendE
 
 	for {
 		select {
+		case <-s.ctx.Done():
+			return status.Error(codes.Unavailable, "server shutting down")
 		case <-stream.Context().Done():
 			return nil
 		case e, ok := <-ch: