[nginx] Limit req: limit_req_dry_run directive.

[Roman Arutyunyan]

details:   https://hg.nginx.org/nginx/rev/2db68852d6a0
branches:  
changeset: 7515:2db68852d6a0
user:      Roman Arutyunyan <arut at nginx.com>
date:      Wed Jun 05 19:55:27 2019 +0300
description:
Limit req: limit_req_dry_run directive.

A new directive limit_req_dry_run allows enabling the dry run mode.  In this
mode requests are neither rejected nor delayed, but reject/delay status is
logged as usual.

diffstat:

 src/http/modules/ngx_http_limit_req_module.c |  29 ++++++++++++++++++++++++---
 1 files changed, 25 insertions(+), 4 deletions(-)

diffs (83 lines):

diff -r 319242d2ddc9 -r 2db68852d6a0 src/http/modules/ngx_http_limit_req_module.c
--- a/src/http/modules/ngx_http_limit_req_module.c	Mon Jun 03 20:33:26 2019 +0300
+++ b/src/http/modules/ngx_http_limit_req_module.c	Wed Jun 05 19:55:27 2019 +0300
@@ -53,6 +53,7 @@ typedef struct {
     ngx_uint_t                   limit_log_level;
     ngx_uint_t                   delay_log_level;
     ngx_uint_t                   status_code;
+    ngx_flag_t                   dry_run;
 } ngx_http_limit_req_conf_t;
 
 
@@ -118,6 +119,13 @@ static ngx_command_t  ngx_http_limit_req
       offsetof(ngx_http_limit_req_conf_t, status_code),
       &ngx_http_limit_req_status_bounds },
 
+    { ngx_string("limit_req_dry_run"),
+      NGX_HTTP_MAIN_CONF|NGX_HTTP_SRV_CONF|NGX_HTTP_LOC_CONF|NGX_CONF_FLAG,
+      ngx_conf_set_flag_slot,
+      NGX_HTTP_LOC_CONF_OFFSET,
+      offsetof(ngx_http_limit_req_conf_t, dry_run),
+      NULL },
+
       ngx_null_command
 };
 
@@ -230,9 +238,10 @@ ngx_http_limit_req_handler(ngx_http_requ
 
         if (rc == NGX_BUSY) {
             ngx_log_error(lrcf->limit_log_level, r->connection->log, 0,
-                          "limiting requests, excess: %ui.%03ui by zone \"%V\"",
-                          excess / 1000, excess % 1000,
-                          &limit->shm_zone->shm.name);
+                        "limiting requests%s, excess: %ui.%03ui by zone \"%V\"",
+                        lrcf->dry_run ? ", dry run" : "",
+                        excess / 1000, excess % 1000,
+                        &limit->shm_zone->shm.name);
         }
 
         while (n--) {
@@ -251,6 +260,10 @@ ngx_http_limit_req_handler(ngx_http_requ
             ctx->node = NULL;
         }
 
+        if (lrcf->dry_run) {
+            return NGX_DECLINED;
+        }
+
         return lrcf->status_code;
     }
 
@@ -267,9 +280,14 @@ ngx_http_limit_req_handler(ngx_http_requ
     }
 
     ngx_log_error(lrcf->delay_log_level, r->connection->log, 0,
-                  "delaying request, excess: %ui.%03ui, by zone \"%V\"",
+                  "delaying request%s, excess: %ui.%03ui, by zone \"%V\"",
+                  lrcf->dry_run ? ", dry run" : "",
                   excess / 1000, excess % 1000, &limit->shm_zone->shm.name);
 
+    if (lrcf->dry_run) {
+        return NGX_DECLINED;
+    }
+
     if (ngx_handle_read_event(r->connection->read, 0) != NGX_OK) {
         return NGX_HTTP_INTERNAL_SERVER_ERROR;
     }
@@ -711,6 +729,7 @@ ngx_http_limit_req_create_conf(ngx_conf_
 
     conf->limit_log_level = NGX_CONF_UNSET_UINT;
     conf->status_code = NGX_CONF_UNSET_UINT;
+    conf->dry_run = NGX_CONF_UNSET;
 
     return conf;
 }
@@ -735,6 +754,8 @@ ngx_http_limit_req_merge_conf(ngx_conf_t
     ngx_conf_merge_uint_value(conf->status_code, prev->status_code,
                               NGX_HTTP_SERVICE_UNAVAILABLE);
 
+    ngx_conf_merge_value(conf->dry_run, prev->dry_run, 0);
+
     return NGX_CONF_OK;
 }