EagleCast

cmd/events.go

@@ -0,0 +1,47 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"log"
+	"time"
+
+	"github.com/labstack/echo/v4"
+)
+
+// EventStream serves an endpoint that never closes and pushes a
+// live event stream (text/event-stream) such as a error messages.
+func (a *App) EventStream(c echo.Context) error {
+	hdr := c.Response().Header()
+	hdr.Set(echo.HeaderContentType, "text/event-stream")
+	hdr.Set(echo.HeaderCacheControl, "no-store")
+	hdr.Set(echo.HeaderConnection, "keep-alive")
+
+	// Subscribe to the event stream with a random ID.
+	id := fmt.Sprintf("api:%v", time.Now().UnixNano())
+	sub, err := a.events.Subscribe(id)
+	if err != nil {
+		log.Fatalf("error subscribing to events: %v", err)
+	}
+
+	ctx := c.Request().Context()
+	for {
+		select {
+		case e := <-sub:
+			b, err := json.Marshal(e)
+			if err != nil {
+				a.log.Printf("error marshalling event: %v", err)
+				continue
+			}
+
+			c.Response().Write([]byte(fmt.Sprintf("retry: 3000\ndata: %s\n\n", b)))
+			c.Response().Flush()
+
+		case <-ctx.Done():
+			// On HTTP connection close, unsubscribe.
+			a.events.Unsubscribe(id)
+			return nil
+		}
+	}
+
+}