91 lines
3.3 KiB
C++
91 lines
3.3 KiB
C++
/*
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* Copyright (c) Facebook, Inc. and its affiliates.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#pragma once
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#include <atomic>
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#include <folly/logging/LogLevel.h>
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namespace folly {
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class LogCategory;
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class LogHandlerConfig;
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class LogMessage;
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/**
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* LogHandler represents a generic API for processing log messages.
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*
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* LogHandlers have an associated log level. The LogHandler will discard any
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* messages below its log level. This allows specific LogHandlers to perform
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* additional filtering of messages even if the messages were enabled at the
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* LogCategory level. For instance, a single LogCategory may have two
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* LogHandlers attached, one that logs locally to a file, and one that sends
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* messages to a remote logging service. The local LogHandler may be
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* configured to record all messages, but the remote LogHandler may want to
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* only process ERROR messages and above, even when debug logging is enabled
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* for this LogCategory.
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*
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* By default the LogHandler level is set to LogLevel::NONE, which means that
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* all log messages will be processed.
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*/
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class LogHandler {
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public:
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virtual ~LogHandler() = default;
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/**
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* handleMessage() is called when a log message is processed by a LogCategory
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* that this handler is attached to.
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*
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* This must be implemented by LogHandler subclasses.
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*
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* handleMessage() will always be invoked from the thread that logged the
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* message. LogMessage::getThreadID() contains the thread ID, but the
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* LogHandler can also include any other thread-local state they desire, and
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* this will always be data for the thread that originated the log message.
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*
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* @param message The LogMessage objet.
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* @param handlerCategory The LogCategory that invoked handleMessage().
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* This is the category that this LogHandler is attached to. Note that
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* this may be different than the category that this message was
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* originally logged at. message->getCategory() returns the category of
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* the log message.
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*/
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virtual void handleMessage(
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const LogMessage& message, const LogCategory* handlerCategory) = 0;
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/**
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* Block until all messages that have already been sent to this LogHandler
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* have been processed.
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*
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* For LogHandlers that perform asynchronous processing of log messages,
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* this ensures that messages already sent to this handler have finished
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* being processed.
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*
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* Other threads may still call handleMessage() while flush() is running.
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* handleMessage() calls that did not complete before the flush() call
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* started will not necessarily be processed by the flush call.
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*/
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virtual void flush() = 0;
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/**
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* Return a LogHandlerConfig object describing the configuration of this
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* LogHandler.
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*/
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virtual LogHandlerConfig getConfig() const = 0;
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};
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} // namespace folly
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