Config: Implement config override with env vars (#502)

* Config: Implement config override with env vars

Implement overriding of configuration from the .conf file with environment variables.
Environment variables keys are autogenerated based on the keys defined in .conf file.
Usage example:
$ export CM_DATA_DIR=/usr
$ CM_WORLD_SERVER_PORT=8080 ./mangosd

* Update env var key format and encapsulated env loading logic.

The new env key format:
Mangosd_Rate_Health
Mangosd_DataDir

* Add suggestions from code review.

* Add missing includes.

src/game/Anticheat/module/anticheat.conf.dist.in

@@ -3,6 +3,16 @@
 #   This file is intended to be used in a setting where the anticheat should run
 #   purely in a read-only mode.  It will do all of its tasks, but take no action,
 #   aside from sending out notifications.  It is intended for testing purposes.
+#
+# 	To overwrite configuration fields with environment variables
+# 	use the following pattern to generate environment variable names:
+#
+# 		For Enable:
+# 			export Anticheat_Enable=0
+#
+# 		For IPBanDelay.Max:
+# 			export Anticheat_IPBanDelay_Max=120
+#
 
 [AnticheatConf]
 ConfVersion=2017102301

src/game/Anticheat/module/libanticheat.cpp

@@ -215,7 +215,7 @@ namespace NamreebAnticheat
 {
 void AnticheatLib::Reload()
 {
-    if (!sAnticheatConfig.SetSource(_LIB_ANTICHEAT_CONFIG))
+    if (!sAnticheatConfig.SetSource(_LIB_ANTICHEAT_CONFIG, "Anticheat_"))
         sLog.outError("[Anticheat] Could not find configuration file %s.", _LIB_ANTICHEAT_CONFIG);
 
     // the configuration setting must be loaded before the database data because the current config settings

src/game/AuctionHouseBot/AuctionHouseBot.cpp

@@ -40,7 +40,7 @@ AuctionHouseBot::~AuctionHouseBot()
 
 void AuctionHouseBot::Initialize()
 {
-    if (!m_ahBotCfg.SetSource(m_configFileName))
+    if (!m_ahBotCfg.SetSource(m_configFileName, "Mangosd_"))
     {
         // set buy/sell chance to 0, this prevents Update() from accessing uninitialized variables
         m_chanceBuy = 0;

src/mangosd/Main.cpp

@@ -141,7 +141,7 @@ int main(int argc, char* argv[])
     }
 #endif
 
-    if (!sConfig.SetSource(configFile))
+    if (!sConfig.SetSource(configFile, "Mangosd_"))
     {
         sLog.outError("Could not find configuration file %s.", configFile.c_str());
         Log::WaitBeforeContinueIfNeed();

src/mangosd/mangosd.conf.dist.in

@@ -1,5 +1,15 @@
 #####################################
-# MaNGOS Configuration file         #
+# MaNGOS Configuration file         
+# 
+# 	To overwrite configuration fields with environment variables
+# 	use the following pattern to generate environment variable names:
+#
+# 		For Rate.Health:
+# 			export Mangosd_Rate_Health=1.2
+#
+# 		For DataDir:
+# 			export Mangosd_DataDir=/tmp
+#
 #####################################
 
 [MangosdConf]

src/realmd/Main.cpp

@@ -120,7 +120,7 @@ int main(int argc, char* argv[])
     }
 #endif
 
-    if (!sConfig.SetSource(configFile))
+    if (!sConfig.SetSource(configFile, "Realmd_"))
     {
         sLog.outError("Could not find configuration file %s.", configFile.c_str());
         Log::WaitBeforeContinueIfNeed();

src/realmd/realmd.conf.dist.in

@@ -1,5 +1,15 @@
 ############################################
-# MaNGOS realmd configuration file         #
+# MaNGOS realmd configuration file
+#
+# 	To overwrite configuration fields with environment variables
+# 	use the following pattern to generate environment variable names:
+#
+# 		For WrongPass.MaxCount:
+# 			export Realmd_WrongPass_MaxCount=10
+#
+# 		For RealmServerPort:
+# 			export Realmd_RealmServerPort=3333
+#
 ############################################
 
 [RealmdConf]

src/shared/Config/Config.cpp

@@ -18,19 +18,26 @@
 
 #include "Config.h"
 #include "Policies/Singleton.h"
+#include "Util/Util.h"
 #include <mutex>
 
 #include <boost/algorithm/string.hpp>
 
 #include <unordered_map>
 #include <string>
 #include <fstream>
+#include <cstdlib>
+#include <optional>
+#include <algorithm>
 
 INSTANTIATE_SINGLETON_1(Config);
 
-bool Config::SetSource(const std::string& file)
+std::optional<std::string> EnvVarForIniKey(std::string const&, std::string const&);
+
+bool Config::SetSource(const std::string& file, const std::string& envVarPrefix)
 {
     m_filename = file;
+    m_envVarPrefix = envVarPrefix;
 
     return Reload();
 }
@@ -62,9 +69,14 @@ bool Config::Reload()
         if (equals == std::string::npos)
             return false;
 
-        auto const entry = boost::algorithm::trim_copy(boost::algorithm::to_lower_copy(line.substr(0, equals)));
-        auto const value = boost::algorithm::trim_copy_if(boost::algorithm::trim_copy(line.substr(equals + 1)), boost::algorithm::is_any_of("\""));
+        auto const trimmedEntry = boost::algorithm::trim_copy(line.substr(0, equals));
+        auto const entry = boost::algorithm::to_lower_copy(trimmedEntry);
+        auto value = boost::algorithm::trim_copy_if(boost::algorithm::trim_copy(line.substr(equals + 1)), boost::algorithm::is_any_of("\""));
 
+        std::optional<std::string> envValue = EnvVarForIniKey(m_envVarPrefix, trimmedEntry);
+        if (envValue)
+            value = *envValue;
+
         newEntries[entry] = value;
     }
     while (in.good());
@@ -85,8 +97,21 @@ const std::string Config::GetStringDefault(const std::string& name, const std::s
     auto const nameLower = boost::algorithm::to_lower_copy(name);
 
     auto const entry = m_entries.find(nameLower);
+
+    if (entry == m_entries.cend())
+    {
+        std::optional<std::string> envVar = EnvVarForIniKey(m_envVarPrefix, name);
+        if (envVar)
+        {
+            sLog.outString("Missing key '%s' in config file '%s', recovered with environment '%s' value.", name.c_str(), m_filename.c_str(), envVar->c_str());
 
-    return entry == m_entries.cend() ? def : entry->second;
+            return *envVar;
+        }
+
+        return def;
+    }
+
+    return entry->second;
 }
 
 bool Config::GetBoolDefault(const std::string& name, bool def) const
@@ -113,3 +138,14 @@ float Config::GetFloatDefault(const std::string& name, float def) const
     return std::stof(value);
 }
 
+std::optional<std::string> EnvVarForIniKey(std::string const& prefix, std::string const& key)
+{
+    std::string escapedKey = key;
+    std::replace(escapedKey.begin(), escapedKey.end(), '.', '_');
+    std::string envKey = prefix + escapedKey;
+    char* val = std::getenv(envKey.c_str());
+    if (!val)
+        return {};
+
+    return std::string(val);
+}

src/shared/Config/Config.h

@@ -31,10 +31,11 @@ class Config
 {
     private:
         std::string m_filename;
+        std::string m_envVarPrefix;
         std::unordered_map<std::string, std::string> m_entries; // keys are converted to lower case.  values cannot be.
 
     public:
-        bool SetSource(const std::string& file);
+        bool SetSource(const std::string& file, const std::string& envVarPrefix);
         bool Reload();
 
         bool IsSet(const std::string& name) const;