folly/folly/logging/LogHandler.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 <atomic>

#include <folly/logging/LogLevel.h>

namespace folly {

class LogCategory;
class LogHandlerConfig;
class LogMessage;

/**
 * LogHandler represents a generic API for processing log messages.
 *
 * LogHandlers have an associated log level.  The LogHandler will discard any
 * messages below its log level.  This allows specific LogHandlers to perform
 * additional filtering of messages even if the messages were enabled at the
 * LogCategory level.  For instance, a single LogCategory may have two
 * LogHandlers attached, one that logs locally to a file, and one that sends
 * messages to a remote logging service.  The local LogHandler may be
 * configured to record all messages, but the remote LogHandler may want to
 * only process ERROR messages and above, even when debug logging is enabled
 * for this LogCategory.
 *
 * By default the LogHandler level is set to LogLevel::NONE, which means that
 * all log messages will be processed.
 */
class LogHandler { … };
} // namespace folly