Core/Config: Implement config override with env vars (#26811)

* Core/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 TC_DATA_DIR=/usr
$ TC_WORLD_SERVER_PORT=8080 ./worldserver

* Core/Config Fix typo in logs

Co-authored-by: Giacomo Pozzoni <giacomopoz@gmail.com>

* Core/Config Fix code style in EnvVarForIniKey

Co-authored-by: Shauren <shauren.trinity@gmail.com>

* Update tests/common/Config.cpp

* Apply suggestions from code review

Co-authored-by: Peter Keresztes Schmidt <carbenium@outlook.com>

* Apply suggestions from code review

Co-authored-by: Peter Keresztes Schmidt <carbenium@outlook.com>

Co-authored-by: Anton Popovichenko <anton.popovichenko@mendix.com>
Co-authored-by: Giacomo Pozzoni <giacomopoz@gmail.com>
Co-authored-by: Shauren <shauren.trinity@gmail.com>
Co-authored-by: Peter Keresztes Schmidt <carbenium@outlook.com>

4 files changed, 139 insertions, 2 deletions

diff --git a/src/common/Configuration/Config.cpp b/src/common/Configuration/Config.cpp
index 5221c4e920b..3471c568491 100644
--- a/src/common/Configuration/Config.cpp
+++ b/src/common/Configuration/Config.cpp
@@ -21,6 +21,7 @@
 #include "Util.h"
 #include <boost/property_tree/ini_parser.hpp>
 #include <algorithm>
+#include <cstdlib>
 #include <memory>
 #include <mutex>
 
@@ -57,6 +58,81 @@ namespace
 
         return true;
     }
+
+    // Converts ini keys to the environment variable key (upper snake case).
+    // Example of conversions:
+    //   SomeConfig => SOME_CONFIG
+    //   myNestedConfig.opt1 => MY_NESTED_CONFIG_OPT_1
+    //   LogDB.Opt.ClearTime => LOG_DB_OPT_CLEAR_TIME
+    std::string IniKeyToEnvVarKey(std::string const& key)
+    {
+        std::string result;
+
+        const char *str = key.c_str();
+        size_t n = key.length();
+
+        char curr;
+        bool isEnd;
+        bool nextIsUpper;
+        bool currIsNumeric;
+        bool nextIsNumeric;
+
+        for (size_t i = 0; i < n; ++i)
+        {
+            curr = str[i];
+            if (curr == ' ' || curr == '.' || curr == '-')
+            {
+                result += '_';
+                continue;
+            }
+
+            isEnd = i == n - 1;
+            if (!isEnd)
+            {
+                nextIsUpper = isupper(str[i + 1]);
+
+                // handle "aB" to "A_B"
+                if (!isupper(curr) && nextIsUpper)
+                {
+                    result += static_cast<char>(std::toupper(curr));
+                    result += '_';
+                    continue;
+                }
+
+                currIsNumeric = isNumeric(curr);
+                nextIsNumeric = isNumeric(str[i + 1]);
+
+                // handle "a1" to "a_1"
+                if (!currIsNumeric && nextIsNumeric)
+                {
+                    result += static_cast<char>(std::toupper(curr));
+                    result += '_';
+                    continue;
+                }
+
+                // handle "1a" to "1_a"
+                if (currIsNumeric && !nextIsNumeric)
+                {
+                    result += static_cast<char>(std::toupper(curr));
+                    result += '_';
+                    continue;
+                }
+            }
+
+            result += static_cast<char>(std::toupper(curr));
+        }
+        return result;
+    }
+
+    Optional<std::string> EnvVarForIniKey(std::string const& key)
+    {
+        std::string envKey = "TC_" + IniKeyToEnvVarKey(key);
+        char* val = std::getenv(envKey.c_str());
+        if (!val)
+            return std::nullopt;
+
+        return std::string(val);
+    }
 }
 
 bool ConfigMgr::LoadInitial(std::string file, std::vector<std::string> args,
@@ -92,6 +168,29 @@ bool ConfigMgr::LoadAdditionalFile(std::string file, bool keepOnReload, std::str
     return true;
 }
 
+std::vector<std::string> ConfigMgr::OverrideWithEnvVariablesIfAny()
+{
+    std::lock_guard<std::mutex> lock(_configLock);
+
+    std::vector<std::string> overriddenKeys;
+
+    for (bpt::ptree::value_type& itr: _config)
+    {
+        if (!itr.second.empty() || itr.first.empty())
+            continue;
+
+        Optional<std::string> envVar = EnvVarForIniKey(itr.first);
+        if (!envVar)
+            continue;
+
+        itr.second = bpt::ptree(*envVar);
+
+        overriddenKeys.push_back(itr.first);
+    }
+
+    return overriddenKeys;
+}
+
 ConfigMgr* ConfigMgr::instance()
 {
     static ConfigMgr instance;
@@ -108,6 +207,8 @@ bool ConfigMgr::Reload(std::vector<std::string>& errors)
         if (!LoadAdditionalFile(additionalFile, false, error))
             errors.push_back(std::move(error));
 
+    OverrideWithEnvVariablesIfAny();
+
     return errors.empty();
 }
 
@@ -120,7 +221,22 @@ T ConfigMgr::GetValueDefault(std::string const& name, T def, bool quiet) const
     }
     catch (bpt::ptree_bad_path const&)
     {
-        if (!quiet)
+        Optional<std::string> envVar = EnvVarForIniKey(name);
+        if (envVar)
+        {
+            Optional<T> castedVar = Trinity::StringTo<T>(*envVar);
+            if (!castedVar)
+            {
+                TC_LOG_ERROR("server.loading", "Bad value defined for name %s in environment variables, going to use default instead", name.c_str());
+                return def;
+            }
+
+            if (!quiet)
+                TC_LOG_WARN("server.loading", "Missing name %s in config file %s, recovered with environment '%s' value.", name.c_str(), _filename.c_str(), envVar->c_str());
+
+            return *castedVar;
+        }
+        else if (!quiet)
         {
             TC_LOG_WARN("server.loading", "Missing name %s in config file %s, add \"%s = %s\" to this file",
                 name.c_str(), _filename.c_str(), name.c_str(), std::to_string(def).c_str());
@@ -144,7 +260,15 @@ std::string ConfigMgr::GetValueDefault<std::string>(std::string const& name, std
     }
     catch (bpt::ptree_bad_path const&)
     {
-        if (!quiet)
+        Optional<std::string> envVar = EnvVarForIniKey(name);
+        if (envVar)
+        {
+            if (!quiet)
+                TC_LOG_WARN("server.loading", "Missing name %s in config file %s, recovered with environment '%s' value.", name.c_str(), _filename.c_str(), envVar->c_str());
+
+            return *envVar;
+        }
+        else if (!quiet)
         {
             TC_LOG_WARN("server.loading", "Missing name %s in config file %s, add \"%s = %s\" to this file",
                 name.c_str(), _filename.c_str(), name.c_str(), def.c_str());
diff --git a/src/common/Configuration/Config.h b/src/common/Configuration/Config.h
index ce1763b4dfd..3e8dabe8ce3 100644
--- a/src/common/Configuration/Config.h
+++ b/src/common/Configuration/Config.h
@@ -34,6 +34,9 @@ public:
     bool LoadInitial(std::string file, std::vector<std::string> args, std::string& error);
     bool LoadAdditionalFile(std::string file, bool keepOnReload, std::string& error);
 
+    /// Overrides configuration with environment variables and returns overridden keys
+    std::vector<std::string> OverrideWithEnvVariablesIfAny();
+
     static ConfigMgr* instance();
 
     bool Reload(std::vector<std::string>& errors);
diff --git a/src/server/authserver/Main.cpp b/src/server/authserver/Main.cpp
index 7a6a5037676..af0acb97236 100644
--- a/src/server/authserver/Main.cpp
+++ b/src/server/authserver/Main.cpp
@@ -108,6 +108,8 @@ int main(int argc, char** argv)
         return 1;
     }
 
+    std::vector<std::string> overriddenKeys = sConfigMgr->OverrideWithEnvVariablesIfAny();
+
     sLog->RegisterAppender<AppenderDB>();
     sLog->Initialize(nullptr);
 
@@ -124,6 +126,9 @@ int main(int argc, char** argv)
         }
     );
 
+    for (std::string const& key : overriddenKeys)
+        TC_LOG_INFO("server.authserver", "Configuration field '%s' was overridden with environment variable.", key.c_str());
+
     // authserver PID file creation
     std::string pidFile = sConfigMgr->GetStringDefault("PidFile", "");
     if (!pidFile.empty())
diff --git a/src/server/worldserver/Main.cpp b/src/server/worldserver/Main.cpp
index 079050e4b7e..418b5de5eb1 100644
--- a/src/server/worldserver/Main.cpp
+++ b/src/server/worldserver/Main.cpp
@@ -146,6 +146,8 @@ extern int main(int argc, char** argv)
         return 1;
     }
 
+    std::vector<std::string> overriddenKeys = sConfigMgr->OverrideWithEnvVariablesIfAny();
+
     std::shared_ptr<Trinity::Asio::IoContext> ioContext = std::make_shared<Trinity::Asio::IoContext>();
 
     sLog->RegisterAppender<AppenderDB>();
@@ -165,6 +167,9 @@ extern int main(int argc, char** argv)
         }
     );
 
+    for (std::string const& key : overriddenKeys)
+        TC_LOG_INFO("server.worldserver", "Configuration field '%s' was overridden with environment variable.", key.c_str());
+
     OpenSSLCrypto::threadsSetup();
 
     std::shared_ptr<void> opensslHandle(nullptr, [](void*) { OpenSSLCrypto::threadsCleanup(); });