add websocket streaming to api rpc handler (#1326)

rpc.go

@@ -104,9 +104,20 @@ func (h *rpcHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	// micro client
 	c := h.opts.Service.Client()
 
+	// create context
+	cx := ctx.FromRequest(r)
+
+	// if stream we currently only support json
+	if isStream(r, service) {
+		serveWebsocket(cx, w, r, service, c)
+		return
+	}
+
 	// create strategy
 	so := selector.WithStrategy(strategy(service.Services))
 
+	// walk the standard call path
+
 	// get payload
 	br, err := requestPayload(r)
 	if err != nil {
@@ -114,9 +125,6 @@ func (h *rpcHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	// create context
-	cx := ctx.FromRequest(r)
-
 	var rsp []byte
 
 	switch {

stream.go

@@ -0,0 +1,150 @@
+package rpc
+
+import (
+	"context"
+	"encoding/json"
+	"net/http"
+	"strings"
+
+	"github.com/gorilla/websocket"
+	"github.com/micro/go-micro/v2/api"
+	"github.com/micro/go-micro/v2/client"
+	"github.com/micro/go-micro/v2/client/selector"
+)
+
+var upgrader = websocket.Upgrader{
+	ReadBufferSize:  1024,
+	WriteBufferSize: 1024,
+}
+
+// serveWebsocket will stream rpc back over websockets assuming json
+func serveWebsocket(ctx context.Context, w http.ResponseWriter, r *http.Request, service *api.Service, c client.Client) {
+	// upgrade the connection
+	conn, err := upgrader.Upgrade(w, r, nil)
+	if err != nil {
+		return
+	}
+	// close on exit
+	defer conn.Close()
+
+	// wait for the first request so we know
+	_, p, err := conn.ReadMessage()
+	if err != nil {
+		return
+	}
+
+	// send to backend
+	// default to trying json
+	var request json.RawMessage
+	// if the extracted payload isn't empty lets use it
+	if len(p) > 0 {
+		request = json.RawMessage(p)
+	}
+
+	// create a request to the backend
+	req := c.NewRequest(
+		service.Name,
+		service.Endpoint.Name,
+		&request,
+		client.WithContentType("application/json"),
+	)
+
+	so := selector.WithStrategy(strategy(service.Services))
+
+	// create a new stream
+	stream, err := c.Stream(ctx, req, client.WithSelectOption(so))
+	if err != nil {
+		return
+	}
+
+	// send the first request for the client
+	// since
+	if err := stream.Send(request); err != nil {
+		return
+	}
+
+	go writeLoop(conn, stream)
+
+	resp := stream.Response()
+
+	// receive from stream and send to client
+	for {
+		// read backend response body
+		body, err := resp.Read()
+		if err != nil {
+			return
+		}
+
+		// write the response
+		if err := conn.WriteMessage(websocket.TextMessage, body); err != nil {
+			return
+		}
+	}
+}
+
+// writeLoop
+func writeLoop(conn *websocket.Conn, stream client.Stream) {
+	// close stream when done
+	defer stream.Close()
+
+	for {
+		_, p, err := conn.ReadMessage()
+		if err != nil {
+			return
+		}
+
+		// send to backend
+		// default to trying json
+		var request json.RawMessage
+		// if the extracted payload isn't empty lets use it
+		if len(p) > 0 {
+			request = json.RawMessage(p)
+		}
+
+		if err := stream.Send(request); err != nil {
+			return
+		}
+	}
+}
+
+func isStream(r *http.Request, srv *api.Service) bool {
+	// check if it's a web socket
+	if !isWebSocket(r) {
+		return false
+	}
+
+	// check if the endpoint supports streaming
+	for _, service := range srv.Services {
+		for _, ep := range service.Endpoints {
+			// skip if it doesn't match the name
+			if ep.Name != srv.Endpoint.Name {
+				continue
+			}
+
+			// matched if the name
+			if v := ep.Metadata["stream"]; v == "true" {
+				return true
+			}
+		}
+	}
+
+	return false
+}
+
+func isWebSocket(r *http.Request) bool {
+	contains := func(key, val string) bool {
+		vv := strings.Split(r.Header.Get(key), ",")
+		for _, v := range vv {
+			if val == strings.ToLower(strings.TrimSpace(v)) {
+				return true
+			}
+		}
+		return false
+	}
+
+	if contains("Connection", "upgrade") && contains("Upgrade", "websocket") {
+		return true
+	}
+
+	return false
+}