backup upstream servers
diff --git a/src/http/ngx_http_upstream.h b/src/http/ngx_http_upstream.h
index b3bb1b4..5c77be3 100644
--- a/src/http/ngx_http_upstream.h
+++ b/src/http/ngx_http_upstream.h
@@ -24,6 +24,7 @@
 #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_NOLIVE          0x40000000
 #define NGX_HTTP_UPSTREAM_FT_OFF             0x80000000