folly/folly/logging/LoggerDB.h

/*
 * Copyright (c) Meta Platforms, Inc. and affiliates.
 *
 * 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.
 */

#pragma once

#include <memory>
#include <string>
#include <unordered_map>
#include <vector>

#include <folly/Conv.h>
#include <folly/CppAttributes.h>
#include <folly/Range.h>
#include <folly/ScopeGuard.h>
#include <folly/Synchronized.h>
#include <folly/detail/StaticSingletonManager.h>
#include <folly/logging/LogName.h>

namespace folly {

class LogCategory;
class LogConfig;
class LogHandler;
class LogHandlerFactory;
enum class LogLevel : uint32_t;

/**
 * LoggerDB stores the set of LogCategory objects.
 */
class LoggerDB { … };

/**
 * initializeLoggerDB() will be called to configure the main LoggerDB singleton
 * the first time that LoggerDB::get() is called.
 *
 * This function can be used apply basic default settings to the LoggerDB,
 * including default log level and log handler settings.
 *
 * A default implementation is provided as a weak symbol, so it can be
 * overridden on a per-program basis if you want to customize the initial
 * LoggerDB settings for your program.
 *
 * However, note that this function may be invoked before main() starts (if
 * other code that runs before main uses the logging library).  Therefore you
 * should be careful about what code runs here.  For instance, you probably
 * should not create LogHandler objects that spawn new threads.  It is
 * generally a good idea to defer more complicated setup until after main()
 * starts.
 *
 * In most situations it is normally better to override getBaseLoggingConfig()
 * from logging/Init.h rather than overriding initializeLoggerDB().  You only
 * need to override initializeLoggerDB() if you want to change the settings
 * that are used for messages that get logged before initLogging() is called.
 *
 * The default implementation configures the root log category to write all
 * warning and higher-level log messages to stderr, using a format similar to
 * that used by GLOG.
 */
void initializeLoggerDB(LoggerDB& db);

FOLLY_ALWAYS_INLINE LoggerDB& LoggerDB::get() { … }

} // namespace folly