Added path_exempt in AccessLogger plugin config to exclude desired path from logging (#2258)

Author: TheEnigmist

lib/inc/drogon/plugins/AccessLogger.h

@@ -36,6 +36,7 @@ namespace plugin
             // "show_microseconds": true,
             // "custom_time_format": "",
             // "use_real_ip": false
+            // "path_exempt": ""
       }
    }
    @endcode
@@ -98,6 +99,10 @@ namespace plugin
  * Enable the plugin by adding the configuration to the list of plugins in the
  * configuration file.
  *
+ * path_exempt: must be a string or a string array, present a regular expression
+ * (for matching the path of a request) or a regular expression list for URLs
+ * that don't have to be logged.
+ *
  */
 class DROGON_EXPORT AccessLogger : public drogon::Plugin<AccessLogger>
 {
@@ -117,6 +122,8 @@ class DROGON_EXPORT AccessLogger : public drogon::Plugin<AccessLogger>
     bool useCustomTimeFormat_{false};
     std::string timeFormat_;
     static bool useRealIp_;
+    std::regex exemptRegex_;
+    bool regexFlag_{false};
 
     using LogFunction = std::function<void(trantor::LogStream &,
                                            const drogon::HttpRequestPtr &,

lib/src/AccessLogger.cc

@@ -113,6 +113,46 @@ void AccessLogger::initAndStart(const Json::Value &config)
     }
     createLogFunctions(format);
     auto logPath = config.get("log_path", "").asString();
+
+    if (config.isMember("path_exempt"))
+    {
+        if (config["path_exempt"].isArray())
+        {
+            const auto &exempts = config["path_exempt"];
+            size_t exemptsCount = exempts.size();
+            if (exemptsCount)
+            {
+                std::string regexString;
+                size_t len = 0;
+                for (const auto &exempt : exempts)
+                {
+                    assert(exempt.isString());
+                    len += exempt.size();
+                }
+                regexString.reserve((exemptsCount * (1 + 2)) - 1 + len);
+
+                const auto last = --exempts.end();
+                for (auto exempt = exempts.begin(); exempt != last; ++exempt)
+                    regexString.append("(")
+                        .append(exempt->asString())
+                        .append(")|");
+                regexString.append("(").append(last->asString()).append(")");
+
+                exemptRegex_ = std::regex(regexString);
+                regexFlag_ = true;
+            }
+        }
+        else if (config["path_exempt"].isString())
+        {
+            exemptRegex_ = std::regex(config["path_exempt"].asString());
+            regexFlag_ = true;
+        }
+        else
+        {
+            LOG_ERROR << "path_exempt must be a string or string array!";
+        }
+    }
+
 #ifdef DROGON_SPDLOG_SUPPORT
     auto logWithSpdlog = trantor::Logger::hasSpdLogSupport() &&
                          config.get("use_spdlog", false).asBool();
@@ -228,7 +268,17 @@ void AccessLogger::initAndStart(const Json::Value &config)
     drogon::app().registerPreSendingAdvice(
         [this](const drogon::HttpRequestPtr &req,
                const drogon::HttpResponsePtr &resp) {
-            logging(LOG_RAW_TO(logIndex_), req, resp);
+            if (regexFlag_)
+            {
+                if (!std::regex_match(req->path(), exemptRegex_))
+                {
+                    logging(LOG_RAW_TO(logIndex_), req, resp);
+                }
+            }
+            else
+            {
+                logging(LOG_RAW_TO(logIndex_), req, resp);
+            }
         });
 }