I’m trying to use server sent event eventsoource through gRPC gateway, so read this
and this and came out with the below proto
syntax = "proto3";
package protobuf;
option go_package = "/proto";
import "google/protobuf/any.proto";
import "google/protobuf/empty.proto";
import "google/api/annotations.proto";
service Events {
rpc StreamEvents (google.protobuf.Empty) returns (stream EventSource) {
option (google.api.http) = {
get: "/v1/rawdata/stream"
};
}
}
message Empty{}
message EventSource {
string event = 1;
google.protobuf.Any data = 2;
}
And generated all required gRPC files (Message/Service/Gateway) using:
protoc -I ./proto \
--go_out ./proto --go_opt paths=source_relative \
--go-grpc_out ./proto --go-grpc_opt paths=source_relative \
--grpc-gateway_out ./proto --grpc-gateway_opt paths=source_relative \
./proto/data.proto
And trying to registered the generated service and gateway at my main app, as:
package main
import (
"context"
"fmt"
"log"
"net"
"net/http"
"os"
"os/signal"
"sync"
"syscall"
"github.com/grpc-ecosystem/grpc-gateway/v2/runtime"
_ "github.com/mattn/go-sqlite3"
"google.golang.org/grpc"
"google.golang.org/grpc/credentials/insecure"
pb "walistner/proto"
)
func main() {
gRPcPort := ":50005"
// Create a gRPC listener on TCP port
lis, err := net.Listen("tcp", gRPcPort)
if err != nil {
log.Fatalf("failed to listen: %v", err)
}
// Create a gRPC server object
s := grpc.NewServer()
// Attach the Greeter service to the server
pb.RegisterEventsServer(s, server{})
log.Println("Serving gRPC server on 0.0.0.0:50005")
// Serve gRPC server
grpcTerminated := make(chan struct{})
go func() {
if err := s.Serve(lis); err != nil {
log.Fatalf("failed to serve: %v", err)
close(grpcTerminated) // In case server is terminated without us requesting this
}
}()
// Create a client connection to the gRPC server we just started
// This is where the gRPC-Gateway proxies the requests
// gateWayTarget := fmt.Sprintf("0.0.0.0%s", gRPcPort)
conn, err := grpc.DialContext(
context.Background(),
gRPcPort,
grpc.WithBlock(),
grpc.WithTransportCredentials(insecure.NewCredentials()),
)
if err != nil {
log.Fatalln("Failed to dial server:", err)
}
gwmux := runtime.NewServeMux()
// This handle to use JSON ServerSentEvent, not the gRPC one
//http.HandleFunc("/sse", passer.HandleSignal)
// Register custom route for GET /hello/{name}
//err = gwmux.HandlePath("GET", "/sse", passer.HandleSignal)
//if err != nil {
// fmt.Println("Error:", err)
//}
// This handler just to confirm server is up and running
// Register custom route for GET /hello/{name}
err = gwmux.HandlePath("GET", "/hello/{name}", func(w http.ResponseWriter, r *http.Request, pathParams map[string]string) {
w.Write([]byte("hello " + pathParams["name"]))
})
if err != nil {
fmt.Println("Error:", err)
}
// Register the gRPC ServerSentEvent
err = pb.RegisterEventsHandler(context.Background(), gwmux, conn)
if err != nil {
log.Fatalln("Failed to register gateway:", err)
}
gwServer := &http.Server{
Addr: ":8090",
Handler: allowCORS(gwmux),
}
log.Println("Serving gRPC-Gateway on http://localhost:8090")
fmt.Println("run POST request of: http://localhost:8090/v1/rawdata/stream")
fmt.Println("or run curl -X GET -k http://localhost:8090/v1/rawdata/stream")
log.Fatal(gwServer.ListenAndServe()) // <- This line alone could be enough ang no need for all the lines after,
// the application is probably doing other things and you will want to be
// able to shutdown cleanly; passing in a context is a good method..
ctx, cancel := context.WithCancel(context.Background())
defer cancel() // Ensure cancel function is called eventually
grpcWebTerminated := make(chan struct{})
var wg sync.WaitGroup
wg.Add(1)
go func() {
defer wg.Done()
if err := gwServer.ListenAndServe(); err != nil {
fmt.Printf("Web server (GRPC) shutdown: %s", err)
}
close(grpcWebTerminated) // In case server is terminated without us requesting this
}()
// Wait for the web server to shutdown OR the context to be cancelled...
select {
case <-ctx.Done():
// Shutdown the servers (there are shutdown commands to request this)
case <-grpcTerminated:
// You may want to exit if this happens (will be due to unexpected error)
case <-grpcWebTerminated:
// You may want to exit if this happens (will be due to unexpected error)
}
// Wait for the goRoutines to complete
<-grpcTerminated
<-grpcWebTerminated
// Listen to Ctrl+C (you can also do something else that prevents the program from exiting)
c := make(chan os.Signal, 1)
signal.Notify(c, os.Interrupt, syscall.SIGTERM)
<-c
if client.IsConnected() {
passer.data <- sseData{
event: "notification",
message: "Server is shut down at the host machine...",
}
client.Disconnect()
}
}
// allowCORS allows Cross Origin Resoruce Sharing from any origin.
// Don't do this without consideration in production systems.
func allowCORS(h http.Handler) http.Handler {
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
if origin := r.Header.Get("Origin"); origin != "" {
w.Header().Set("Access-Control-Allow-Origin", origin)
}
h.ServeHTTP(w, r)
})
}
And the main part that is having an issue, is ther gateway registration:
package main
import (
"fmt"
"log"
"sync"
pb "walistner/proto"
"google.golang.org/grpc/metadata"
"google.golang.org/grpc/peer"
"google.golang.org/protobuf/reflect/protoreflect"
"google.golang.org/protobuf/types/known/anypb"
"google.golang.org/protobuf/types/known/emptypb"
)
type server struct {
pb.UnimplementedEventsServer
}
func (s server) StreamEvents(_ *emptypb.Empty, srv pb.Events_StreamEventsServer) error {
if p, ok := peer.FromContext(srv.Context()); ok {
fmt.Println("Client ip is:", p.Addr.String())
}
md := metadata.New(map[string]string{"Content-Type": "text/event-stream", "Connection": "keep-alive"})
srv.SetHeader(md)
//use wait group to allow process to be concurrent
var wg sync.WaitGroup
for {
incomingInput := <-passer.data
wg.Add(1)
//go func(count int64) {
go func() {
defer wg.Done()
myData := incomingInput.data <---------------This is a string
// Convert data to *anypb.Any
data, err := anypb.New(myData.(protoreflect.ProtoMessage)) <----- tried this but it failed
if err != nil {
//...
}
resp := pb.EventSource{
Event: incomingInput.event,
Data: data, // <---------- this is required to be of type *anypb.Any
}
if err := srv.Send(&resp); err != nil {
log.Printf("send error %v", err)
}
}()
}
wg.Wait()
return nil
}
My data structure inside the go app is:
type sseData struct {
event, message string
}
type DataPasser struct {
data chan sseData
logs chan string
connection chan struct{} // To control maximum allowed clients connections
}
var passer *DataPasser
func init() {
passer = &DataPasser{
data: make(chan sseData),
logs: make(chan string),
connection: make(chan struct{}, maxClients),
}
}