// Copyright 2016-2018, Pulumi Corporation. All rights reserved. package rpcutil import ( "net" "strconv" "strings" "github.com/pkg/errors" "google.golang.org/grpc" "google.golang.org/grpc/reflection" ) // IsBenignCloseErr returns true if the error is "expected" upon shutdown of the server. func IsBenignCloseErr(err error) bool { msg := err.Error() return strings.HasSuffix(msg, "use of closed network connection") || strings.HasSuffix(msg, "grpc: the server has been stopped") } // Serve creates a new gRPC server, calls out to the supplied registration functions to bind interfaces, and then // listens on the supplied TCP port. If the caller wishes for the kernel to choose a free port automatically, pass 0 as // the port number. The return values are: the chosen port (the same as supplied if non-0), a channel that may // eventually return an error, and an error, in case something went wrong. The channel is non-nil and waits until // the server is finished, in the case of a successful launch of the RPC server. func Serve(port int, cancel chan bool, registers []func(*grpc.Server) error) (int, chan error, error) { // Listen on a TCP port, but let the kernel choose a free port for us. lis, err := net.Listen("tcp", "127.0.0.1:"+strconv.Itoa(port)) if err != nil { return port, nil, errors.Errorf("failed to listen on TCP port ':%v': %v", port, err) } // Now new up a gRPC server and register any RPC interfaces the caller wants. srv := grpc.NewServer(grpc.UnaryInterceptor(OpenTracingServerInterceptor())) for _, register := range registers { if err := register(srv); err != nil { return port, nil, errors.Errorf("failed to register RPC handler: %v", err) } } reflection.Register(srv) // enable reflection. // If the port was 0, look up what port the kernel chosen, by accessing the underlying TCP listener/address. if port == 0 { tcpl := lis.(*net.TCPListener) tcpa := tcpl.Addr().(*net.TCPAddr) port = tcpa.Port } // If the caller provided a cancellation channel, start a goroutine that will gracefully terminate the gRPC server when // that channel is closed or receives a `true` value. if cancel != nil { go func() { for v, ok := <-cancel; !v && ok; v, ok = <-cancel { } srv.GracefulStop() }() } // Finally, serve; this returns only once the server shuts down (e.g., due to a signal). done := make(chan error) go func() { if err := srv.Serve(lis); err != nil && !IsBenignCloseErr(err) { done <- errors.Errorf("stopped serving: %v", err) } else { done <- nil // send a signal so caller knows we're done, even though it's nil. } close(done) }() return port, done, nil }