feat(variables): add new variable $kong_request_id (#70)

Similar to `$request_id`, but from pseudo-random number source instead of OpenSSL's `RAND_bytes`
for better performance.

KAG-2734
---------

Co-authored-by: Datong Sun <datong.sun@konghq.com>

README.md

@@ -13,6 +13,8 @@ Table of Contents
     * [lua\_kong\_load\_var\_index](#lua_kong_load_var_index)
     * [lua\_kong\_set\_static\_tag](#lua_kong_set_static_tag)
     * [lua\_kong\_error\_log\_request\_id](#lua_kong_error_log_request_id)
+* [Variables](#variables)
+    * [$kong\_request\_id](#kong_request_id)
 * [Methods](#methods)
     * [resty.kong.tls.disable\_session\_reuse](#restykongtlsdisable_session_reuse)
     * [resty.kong.tls.get\_full\_client\_certificate\_chain](#restykongtlsget_full_client_certificate_chain)
@@ -160,6 +162,16 @@ An error log line may look similar to the following:
 
 [Back to TOC](#table-of-contents)
 
+Variables
+=========
+
+$kong\_request\_id
+------------------
+Unique request identifier generated from 16 pseudo-random bytes, in hexadecimal.
+This variable is indexed.
+
+[Back to TOC](#table-of-contents)
+
 Methods
 =======
 

config

@@ -3,11 +3,12 @@ ngx_module_name=ngx_http_lua_kong_module
 ngx_module_srcs=" \
                 $ngx_addon_dir/src/ngx_http_lua_kong_grpc.c \
                 $ngx_addon_dir/src/ngx_http_lua_kong_ssl.c \
-                $ngx_addon_dir/src/ngx_http_lua_kong_var.c \
+                $ngx_addon_dir/src/ngx_http_lua_kong_var_index.c \
                 $ngx_addon_dir/src/ngx_http_lua_kong_tag.c \
                 $ngx_addon_dir/src/ngx_http_lua_kong_module.c \
                 $ngx_addon_dir/src/ngx_http_lua_kong_log.c \
                 $ngx_addon_dir/src/ngx_http_lua_kong_log_handler.c \
+                $ngx_addon_dir/src/ngx_http_lua_kong_vars.c \
                 $ngx_addon_dir/src/ssl/ngx_lua_kong_ssl.c \
                 "
 

src/ngx_http_lua_kong_common.h

@@ -52,4 +52,7 @@ ngx_http_lua_kong_ctx_t *ngx_http_lua_kong_get_module_ctx(
 char *ngx_http_lua_kong_error_log_init(
     ngx_conf_t *cf);
 
+ngx_int_t
+ngx_http_lua_kong_add_vars(ngx_conf_t *cf);
+
 #endif /* _NGX_HTTP_LUA_KONG_COMMON_H_INCLUDED_ */

src/ngx_http_lua_kong_module.c

@@ -24,7 +24,7 @@ static char* ngx_http_lua_kong_merge_loc_conf(ngx_conf_t *cf, void *parent, void
 
 
 static ngx_http_module_t ngx_http_lua_kong_module_ctx = {
-    NULL,                                    /* preconfiguration */
+    ngx_http_lua_kong_add_vars,              /* preconfiguration */
     ngx_http_lua_kong_init,                  /* postconfiguration */
 
     NULL,                                    /* create main configuration */

src/ngx_http_lua_kong_var.c → src/ngx_http_lua_kong_var_index.c

@@ -72,7 +72,7 @@ static ngx_str_t default_vars[] = {
     ngx_string("server_addr"),
     ngx_string("server_port"),
 
-/* --with-http_ssl_module */
+    /* --with-http_ssl_module */
 #if (NGX_SSL)
     ngx_string("ssl_cipher"),
     ngx_string("ssl_client_raw_cert"),
@@ -86,6 +86,9 @@ static ngx_str_t default_vars[] = {
     ngx_string("upstream_http_upgrade"),
     ngx_string("upstream_status"),
 
+    /* lua-kong-module vars */
+    ngx_string("kong_request_id"),
+
     ngx_null_string
 };
 

src/ngx_http_lua_kong_vars.c

@@ -0,0 +1,81 @@
+/**
+ * Copyright 2019-2023 Kong Inc.
+
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+
+ *    http://www.apache.org/licenses/LICENSE-2.0
+
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+
+#include "ngx_http_lua_kong_common.h"
+
+
+#define NGX_HTTP_LUA_KONG_RANDOM_COUNT         4
+#define NGX_HTTP_LUA_KONG_UINT32_HEX_LEN       sizeof(uint32_t) * 2
+
+
+static ngx_int_t
+ngx_http_lua_kong_variable_request_id(ngx_http_request_t *r,
+    ngx_http_variable_value_t *v, uintptr_t data)
+{
+    u_char     *id;
+    uint32_t    i, rnd;
+
+    id = ngx_pnalloc(r->pool,
+                     NGX_HTTP_LUA_KONG_RANDOM_COUNT *
+                     NGX_HTTP_LUA_KONG_UINT32_HEX_LEN);
+    if (id == NULL) {
+        return NGX_ERROR;
+    }
+
+    v->valid = 1;
+    v->no_cacheable = 0;
+    v->not_found = 0;
+
+    v->len = NGX_HTTP_LUA_KONG_RANDOM_COUNT *
+             NGX_HTTP_LUA_KONG_UINT32_HEX_LEN;
+    v->data = id;
+
+    for (i = 0; i < NGX_HTTP_LUA_KONG_RANDOM_COUNT; i++) {
+        rnd = (uint32_t) ngx_random();
+        id = ngx_hex_dump(id, (u_char *) &rnd, sizeof(uint32_t));
+    }
+
+    return NGX_OK;
+}
+
+
+static ngx_http_variable_t  ngx_http_lua_kong_variables[] = {
+
+    { ngx_string("kong_request_id"), NULL,
+      ngx_http_lua_kong_variable_request_id,
+      0, 0, 0 },
+
+      ngx_http_null_variable
+};
+
+
+ngx_int_t
+ngx_http_lua_kong_add_vars(ngx_conf_t *cf)
+{
+    ngx_http_variable_t        *cv, *v;
+
+    for (cv = ngx_http_lua_kong_variables; cv->name.len; cv++) {
+        v = ngx_http_add_variable(cf, &cv->name, cv->flags);
+        if (v == NULL) {
+            return NGX_ERROR;
+        }
+
+        *v = *cv;
+    }
+
+    return NGX_OK;
+}

t/009-error-log-append.t

@@ -233,3 +233,27 @@ GET /test
 [error]
 [crit]
 [alert]
+
+
+=== TEST 9: $kong_request_id is appended correctly to error logs
+--- http_config
+    lua_package_path "../lua-resty-core/lib/?.lua;lualib/?.lua;;";
+    lua_kong_error_log_request_id $kong_request_id;
+--- config
+    location = /test {
+        content_by_lua_block {
+            ngx.log(ngx.INFO, "log_msg")
+            ngx.exit(200)
+        }
+    }
+--- request
+GET /test
+--- error_code: 200
+--- error_log eval
+qr/log_msg.*request_id: "[0-9a-f]{32}"$/
+--- no_error_log
+[error]
+[crit]
+[alert]
+
+

t/010-request-id.t

@@ -0,0 +1,41 @@
+# vim:set ft= ts=4 sw=4 et:
+
+use Test::Nginx::Socket::Lua;
+use Cwd qw(cwd);
+
+repeat_each(2);
+
+plan tests => repeat_each() * (blocks() * 5);
+
+my $pwd = cwd();
+
+$ENV{TEST_NGINX_HTML_DIR} ||= html_dir();
+
+no_long_string();
+
+run_tests();
+
+__DATA__
+
+=== TEST 1: $kong_request_id works
+--- config
+    location /t {
+        content_by_lua_block {
+            local rid = ngx.var.kong_request_id
+            assert(ngx.re.match(rid, "[0-9a-f]{32}"))
+            ngx.say("ok")
+        }
+    }
+
+--- request
+GET /t
+--- response_body_like
+ok
+
+--- error_code: 200
+--- no_error_log
+[error]
+[crit]
+[alert]
+
+