fix: send periodic SSE keepalive while waiting for upstream image response

relay/image_handler.go

@@ -6,6 +6,7 @@ import (
 	"io"
 	"net/http"
 	"strings"
+	"time"
 
 	"github.com/QuantumNous/new-api/common"
 	"github.com/QuantumNous/new-api/constant"
@@ -92,22 +93,37 @@ func ImageHelper(c *gin.Context, info *relaycommon.RelayInfo) (newAPIError *type
 
 	statusCodeMappingStr := c.GetString("status_code_mapping")
 
-	// When the client requests streaming, send SSE headers and an initial
-	// keepalive comment immediately.  This prevents reverse-proxies (Nginx
-	// etc.) from closing the connection due to proxy_read_timeout while the
-	// backend is waiting for the upstream image API to respond (which can
-	// take 60+ seconds).  The downstream handlers
-	// (OpenaiImageStreamHandler / OpenaiImageJSONAsStreamHandler) call
-	// SetEventStreamHeaders again, but that function is idempotent.
+	// When the client requests streaming, send SSE headers immediately and
+	// start a periodic keepalive goroutine.  Image generation can take 60+
+	// seconds; without periodic data the connection will be closed by
+	// reverse-proxies (Nginx proxy_read_timeout) or the browser.
+	var keepaliveDone chan struct{}
 	if info.IsStream {
 		helper.SetEventStreamHeaders(c)
 		c.Status(http.StatusOK)
-		// SSE comment keeps the connection alive through proxies
 		fmt.Fprint(c.Writer, ": keepalive\n\n")
 		_ = helper.FlushWriter(c)
+
+		keepaliveDone = make(chan struct{})
+		go func() {
+			ticker := time.NewTicker(15 * time.Second)
+			defer ticker.Stop()
+			for {
+				select {
+				case <-ticker.C:
+					fmt.Fprint(c.Writer, ": keepalive\n\n")
+					_ = helper.FlushWriter(c)
+				case <-keepaliveDone:
+					return
+				}
+			}
+		}()
 	}
 
 	resp, err := adaptor.DoRequest(c, info, requestBody)
+	if keepaliveDone != nil {
+		close(keepaliveDone)
+	}
 	if err != nil {
 		logImageError(c, info, request, fmt.Sprintf("请求失败: %s", err.Error()))
 		if info.IsStream {