Add support for nginx_upstream_check_module module

[pfischermx]

I believe the nginx_upstream_check_module is widely used for checking upstreams and we find this patch very useful for updating the upstream status as soon as the healthcheck fails. It check the upstream status if the nginx_upstream_check_module module is enabled/defined.

[vozlt]

Thanks PR.
But I'm not going to test this patch.
Please note that I will remove this patch from master if something goes wrong.

[ergoz]

after this patch i cant build openresty 1.19.3.1 from sources with error:

/tmp/nginx-module-vts/src/ngx_http_vhost_traffic_status_display_json.c: In function 'ngx_http_vhost_traffic_status_display_set_upstream_group':
/tmp/nginx-module-vts/src/ngx_http_vhost_traffic_status_display_json.c:586:59: error: 'ngx_http_upstream_rr_peer_t' {aka 'struct ngx_http_upstream_rr_peer_s'} has no member named 'check_index'
  586 |                 if (ngx_http_upstream_check_peer_down(peer->check_index)) {
      |                                                           ^~
make[2]: *** [objs/Makefile:3749: objs/addon/src/ngx_http_vhost_traffic_status_display_json.o] Error 1

how to fix it?

[vozlt]

@ergoz
The peer->check_index variable is defined in the nginx_upstream_check_module and it looks like it can be used only by patching it in nginx.
If it continues to be a problem, remove it as below!

--- ngx_http_vhost_traffic_status_display_json.c        2021-01-25 00:21:14.610002559 +0900
+++ ngx_http_vhost_traffic_status_display_json.c.o      2022-09-05 23:43:21.015685286 +0900
@@ -10,10 +10,6 @@
 #include "ngx_http_vhost_traffic_status_display_json.h"
 #include "ngx_http_vhost_traffic_status_display.h"
 
-#if (NGX_HTTP_UPSTREAM_CHECK)
-#include "ngx_http_upstream_check_module.h"
-#endif
-
 
 u_char *
 ngx_http_vhost_traffic_status_display_set_main(ngx_http_request_t *r,
@@ -582,17 +578,7 @@ ngx_http_vhost_traffic_status_display_se
                 usn.max_fails = peer->max_fails;
                 usn.fail_timeout = peer->fail_timeout;
                 usn.backup = 0;
-#if (NGX_HTTP_UPSTREAM_CHECK)
-                if (ngx_http_upstream_check_peer_down(peer->check_index)) {
-                    usn.down = 1;
-
-                } else {
-                    usn.down = 0;
-                }
-#else
                 usn.down = (peer->fails >= peer->max_fails || peer->down);
-#endif
-
 #if nginx_version > 1007001
                 usn.name = peer->name;
 #endif