Handle 503 HTTP code to schedule member change check

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

client/http/client.go

@@ -124,6 +124,8 @@ func (ci *clientInner) requestWithRetry(
 		err        error
 	)
 	execFunc := func() error {
+		// Handle some special status codes to increase the success rate of the following requests.
+		defer ci.handleHTTPStatusCode(statusCode)
 		// It will try to send the request to the PD leader first and then try to send the request to the other PD followers.
 		clients := ci.sd.GetAllServiceClients()
 		if len(clients) == 0 {
@@ -153,13 +155,21 @@ func (ci *clientInner) requestWithRetry(
 	}
 	// Copy a new backoffer for each request.
 	bo := *reqInfo.bo
-	// Backoffer also needs to check the status code to determine whether to retry.
+	// Set the retryable checker for the backoffer.
 	bo.SetRetryableChecker(func(err error) bool {
+		// Backoffer also needs to check the status code to determine whether to retry.
 		return err != nil && !noNeedRetry(statusCode)
 	})
 	return bo.Exec(ctx, execFunc)
 }
 
+func (ci *clientInner) handleHTTPStatusCode(code int) {
+	// If the status code is 503, it indicates that there may be PD leader/follower changes.
+	if code == http.StatusServiceUnavailable {
+		ci.sd.ScheduleCheckMemberChanged()
+	}
+}
+
 func noNeedRetry(statusCode int) bool {
 	return statusCode == http.StatusNotFound ||
 		statusCode == http.StatusForbidden ||