perf(request-id): use proxy_set_header instead of `ngx.req.set_head…

…er` (#11788)

Utilize the Nginx directive
`proxy_set_header X-Kong-Request-Id $kong_request_id` instead of Lua
call `set_header()` can enhance the RPS by ~2%
in the testing scenario where no plugins are enabled.

KAG-2814

kong/runloop/handler.lua

@@ -43,7 +43,6 @@ local log               = ngx.log
 local exit              = ngx.exit
 local exec              = ngx.exec
 local header            = ngx.header
-local set_header        = ngx.req.set_header
 local timer_at          = ngx.timer.at
 local subsystem         = ngx.config.subsystem
 local clear_header      = ngx.req.clear_header
@@ -1329,9 +1328,6 @@ return {
     end,
     -- Only executed if the `router` module found a route and allows nginx to proxy it.
     after = function(ctx)
-      local enabled_headers_upstream = kong.configuration.enabled_headers_upstream
-      local headers = constants.HEADERS
-
       -- Nginx's behavior when proxying a request with an empty querystring
       -- `/foo?` is to keep `$is_args` an empty string, hence effectively
       -- stripping the empty querystring.
@@ -1426,16 +1422,6 @@ return {
       if var.http_proxy_connection then
         clear_header("Proxy-Connection")
       end
-
-      -- X-Kong-Request-Id upstream header
-      local rid, rid_get_err = request_id_get()
-      if not rid then
-        log(WARN, "failed to get Request ID: ", rid_get_err)
-      end
-
-      if enabled_headers_upstream[headers.REQUEST_ID] and rid then
-        set_header(headers.REQUEST_ID, rid)
-      end
     end
   },
   header_filter = {

kong/templates/nginx_kong.lua

@@ -156,6 +156,9 @@ server {
         proxy_set_header      X-Forwarded-Path   $upstream_x_forwarded_path;
         proxy_set_header      X-Forwarded-Prefix $upstream_x_forwarded_prefix;
         proxy_set_header      X-Real-IP          $remote_addr;
+> if enabled_headers_upstream["X-Kong-Request-Id"] then
+        proxy_set_header      X-Kong-Request-Id  $kong_request_id;
+> end
         proxy_pass_header     Server;
         proxy_pass_header     Date;
         proxy_ssl_name        $upstream_host;
@@ -187,6 +190,9 @@ server {
         proxy_set_header      X-Forwarded-Path   $upstream_x_forwarded_path;
         proxy_set_header      X-Forwarded-Prefix $upstream_x_forwarded_prefix;
         proxy_set_header      X-Real-IP          $remote_addr;
+> if enabled_headers_upstream["X-Kong-Request-Id"] then
+        proxy_set_header      X-Kong-Request-Id  $kong_request_id;
+> end
         proxy_pass_header     Server;
         proxy_pass_header     Date;
         proxy_ssl_name        $upstream_host;
@@ -218,6 +224,9 @@ server {
         proxy_set_header      X-Forwarded-Path   $upstream_x_forwarded_path;
         proxy_set_header      X-Forwarded-Prefix $upstream_x_forwarded_prefix;
         proxy_set_header      X-Real-IP          $remote_addr;
+> if enabled_headers_upstream["X-Kong-Request-Id"] then
+        proxy_set_header      X-Kong-Request-Id  $kong_request_id;
+> end
         proxy_pass_header     Server;
         proxy_pass_header     Date;
         proxy_ssl_name        $upstream_host;
@@ -249,6 +258,9 @@ server {
         proxy_set_header      X-Forwarded-Path   $upstream_x_forwarded_path;
         proxy_set_header      X-Forwarded-Prefix $upstream_x_forwarded_prefix;
         proxy_set_header      X-Real-IP          $remote_addr;
+> if enabled_headers_upstream["X-Kong-Request-Id"] then
+        proxy_set_header      X-Kong-Request-Id  $kong_request_id;
+> end
         proxy_pass_header     Server;
         proxy_pass_header     Date;
         proxy_ssl_name        $upstream_host;
@@ -273,6 +285,9 @@ server {
         grpc_set_header      X-Forwarded-Path   $upstream_x_forwarded_path;
         grpc_set_header      X-Forwarded-Prefix $upstream_x_forwarded_prefix;
         grpc_set_header      X-Real-IP          $remote_addr;
+> if enabled_headers_upstream["X-Kong-Request-Id"] then
+        grpc_set_header      X-Kong-Request-Id  $kong_request_id;
+> end
         grpc_pass_header     Server;
         grpc_pass_header     Date;
         grpc_ssl_name        $upstream_host;
@@ -316,6 +331,9 @@ server {
         proxy_set_header      X-Forwarded-Path   $upstream_x_forwarded_path;
         proxy_set_header      X-Forwarded-Prefix $upstream_x_forwarded_prefix;
         proxy_set_header      X-Real-IP          $remote_addr;
+> if enabled_headers_upstream["X-Kong-Request-Id"] then
+        proxy_set_header      X-Kong-Request-Id  $kong_request_id;
+> end
         proxy_pass_header     Server;
         proxy_pass_header     Date;
         proxy_ssl_name        $upstream_host;