Streams (#68)

streams/handler/subscribe.go

@@ -0,0 +1,64 @@
+package handler
+
+import (
+	"context"
+
+	"github.com/micro/micro/v3/service/errors"
+	"github.com/micro/micro/v3/service/events"
+	"github.com/micro/micro/v3/service/logger"
+	pb "github.com/micro/services/streams/proto"
+	"google.golang.org/protobuf/types/known/timestamppb"
+	"gorm.io/gorm"
+)
+
+func (s *Streams) Subscribe(ctx context.Context, req *pb.SubscribeRequest, stream pb.Streams_SubscribeStream) error {
+	// validate the request
+	if len(req.Token) == 0 {
+		return ErrMissingToken
+	}
+	if len(req.Topic) == 0 {
+		return ErrMissingTopic
+	}
+
+	// find the token and check to see if it has expired
+	var token Token
+	if err := s.DB.Where(&Token{Token: req.Token}).First(&token).Error; err == gorm.ErrRecordNotFound {
+		return ErrInvalidToken
+	} else if err != nil {
+		logger.Errorf("Error reading token from store: %v", err)
+		return errors.InternalServerError("DATABASE_ERROR", "Error reading token from database")
+	}
+	if token.ExpiresAt.Before(s.Time()) {
+		return ErrExpiredToken
+	}
+
+	// if the token was scoped to a channel, ensure the channel is the one being requested
+	if len(token.Topic) > 0 && token.Topic != req.Topic {
+		return ErrForbiddenTopic
+	}
+
+	// start the subscription
+	evChan, err := s.Events.Consume(req.Topic, events.WithGroup(token.Token))
+	if err != nil {
+		logger.Errorf("Error connecting to events stream: %v", err)
+		return errors.InternalServerError("EVENTS_ERROR", "Error connecting to events stream")
+	}
+	go func() {
+		defer stream.Close()
+		for {
+			msg, ok := <-evChan
+			if !ok {
+				return
+			}
+			if err := stream.Send(&pb.Message{
+				Topic:   msg.Topic,
+				Message: string(msg.Payload),
+				SentAt:  timestamppb.New(msg.Timestamp),
+			}); err != nil {
+				return
+			}
+		}
+	}()
+
+	return nil
+}