address comments

Signed-off-by: lhy1024 <[email protected]>

pkg/utils/apiutil/apiutil.go

@@ -436,9 +436,13 @@ func (p *customReverseProxies) ServeHTTP(w http.ResponseWriter, r *http.Request)
 		}
 
 		// We need to copy the response headers before we write the header.
-		// Otherwise, we cannot set the header.
+		// Otherwise, we cannot set the header after w.WriteHeader() is called.
 		// And we need to write the header before we copy the response body.
-		// Otherwise, we cannot set the status code.
+		// Otherwise, we cannot set the status code after w.Write() is called.
+		// In other words, we must perform the following steps strictly in order:
+		// 1. Set the response headers.
+		// 2. Write the response header.
+		// 3. Write the response body.
 		copyHeader(w.Header(), resp.Header)
 		w.WriteHeader(resp.StatusCode)
 
@@ -460,10 +464,11 @@ func (p *customReverseProxies) ServeHTTP(w http.ResponseWriter, r *http.Request)
 	http.Error(w, ErrRedirectFailed, http.StatusInternalServerError)
 }
 
+// copyHeader duplicates the HTTP headers from the source `src` to the destination `dst`.
+// It skips the "Content-Encoding" and "Content-Length" headers because they should be set by `http.ResponseWriter`.
+// These headers may be modified after a redirect when gzip compression is enabled.
 func copyHeader(dst, src http.Header) {
 	for k, vv := range src {
-		// skip Content-Encoding and Content-Length header
-		// because they need to be set by http.ResponseWriter when gzip is enabled
 		if k == "Content-Encoding" || k == "Content-Length" {
 			continue
 		}

pkg/utils/apiutil/serverapi/middleware.go

@@ -116,6 +116,9 @@ func (h *redirector) matchMicroServiceRedirectRules(r *http.Request) (bool, stri
 					zap.String("path", r.URL.Path))
 			}
 			// Extract parameters from the URL path
+			// e.g. matchPath = /pd/api/v1/operator/1
+			//      targetPath = /scheduling/api/v1/operator
+			//      r.URL.Path = /scheduling/api/v1/operator/1
 			pathParams := strings.TrimPrefix(r.URL.Path, rule.matchPath)
 			if len(pathParams) > 0 && pathParams[0] == '/' {
 				pathParams = pathParams[1:] // Remove leading '/'
@@ -129,10 +132,10 @@ func (h *redirector) matchMicroServiceRedirectRules(r *http.Request) (bool, stri
 }
 
 func (h *redirector) ServeHTTP(w http.ResponseWriter, r *http.Request, next http.HandlerFunc) {
-	needRedirectToMicroService, targetAddr := h.matchMicroServiceRedirectRules(r)
+	redirectToMicroService, targetAddr := h.matchMicroServiceRedirectRules(r)
 	allowFollowerHandle := len(r.Header.Get(apiutil.PDAllowFollowerHandleHeader)) > 0
 	isLeader := h.s.GetMember().IsLeader()
-	if !h.s.IsClosed() && (allowFollowerHandle || isLeader) && !needRedirectToMicroService {
+	if !h.s.IsClosed() && (allowFollowerHandle || isLeader) && !redirectToMicroService {
 		next(w, r)
 		return
 	}
@@ -157,7 +160,7 @@ func (h *redirector) ServeHTTP(w http.ResponseWriter, r *http.Request, next http
 	}
 
 	var clientUrls []string
-	if needRedirectToMicroService {
+	if redirectToMicroService {
 		if len(targetAddr) == 0 {
 			http.Error(w, apiutil.ErrRedirectFailed, http.StatusInternalServerError)
 			return