--- a/src/http/ngx_http_upstream.h
+++ b/src/http/ngx_http_upstream.h
@@ -20,13 +20,20 @@
 #define NGX_HTTP_UPSTREAM_FT_TIMEOUT         0x00000004
 #define NGX_HTTP_UPSTREAM_FT_INVALID_HEADER  0x00000008
 #define NGX_HTTP_UPSTREAM_FT_HTTP_500        0x00000010
-#define NGX_HTTP_UPSTREAM_FT_HTTP_503        0x00000020
-#define NGX_HTTP_UPSTREAM_FT_HTTP_404        0x00000040
-#define NGX_HTTP_UPSTREAM_FT_BUSY_LOCK       0x00000080
-#define NGX_HTTP_UPSTREAM_FT_MAX_WAITING     0x00000100
+#define NGX_HTTP_UPSTREAM_FT_HTTP_502        0x00000020
+#define NGX_HTTP_UPSTREAM_FT_HTTP_503        0x00000040
+#define NGX_HTTP_UPSTREAM_FT_HTTP_504        0x00000080
+#define NGX_HTTP_UPSTREAM_FT_HTTP_404        0x00000100
+#define NGX_HTTP_UPSTREAM_FT_BUSY_LOCK       0x00000200
+#define NGX_HTTP_UPSTREAM_FT_MAX_WAITING     0x00000400
 #define NGX_HTTP_UPSTREAM_FT_NOLIVE          0x40000000
 #define NGX_HTTP_UPSTREAM_FT_OFF             0x80000000
 
+#define NGX_HTTP_UPSTREAM_FT_STATUS          (NGX_HTTP_UPSTREAM_FT_HTTP_500  \
+                                             |NGX_HTTP_UPSTREAM_FT_HTTP_502  \
+                                             |NGX_HTTP_UPSTREAM_FT_HTTP_503  \
+                                             |NGX_HTTP_UPSTREAM_FT_HTTP_504  \
+                                             |NGX_HTTP_UPSTREAM_FT_HTTP_404)
 
 #define NGX_HTTP_UPSTREAM_INVALID_HEADER     40
 
@@ -267,6 +274,12 @@ struct ngx_http_upstream_s {
 };
 
 
+typedef struct {
+    ngx_uint_t                      status;
+    ngx_uint_t                      mask;
+} ngx_http_upstream_next_t;
+
+
 ngx_int_t ngx_http_upstream_header_variable(ngx_http_request_t *r,
     ngx_http_variable_value_t *v, uintptr_t data);