async_logger.h

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// Copyright(c) 2015-present, Gabi Melman & spdlog contributors.
// Distributed under the MIT License (http://opensource.org/licenses/MIT)
 
#pragma once
 
// Fast asynchronous logger.
// Uses pre allocated queue.
// Creates a single back thread to pop messages from the queue and log them.
//
// Upon each log write the logger:
//    1. Checks if its log level is enough to log the message
//    2. Push a new copy of the message to a queue (or block the caller until
//    space is available in the queue)
// Upon destruction, logs all remaining messages in the queue before
// destructing..
 
#include <spdlog/logger.h>
 
namespace spdlog
{
 
    // Async overflow policy - block by default.
    enum class async_overflow_policy
    {
        block,         // Block until message can be enqueued
        overrun_oldest // Discard oldest message in the queue if full when trying to
                       // add new item.
    };
 
    namespace details
    {
        class thread_pool;
    }
 
    class SPDLOG_API async_logger final : public std::enable_shared_from_this<async_logger>, public logger
    {
        friend class details::thread_pool;
 
    public:
        template <typename It>
        async_logger(std::string logger_name, It begin, It end, std::weak_ptr<details::thread_pool> tp, async_overflow_policy overflow_policy = async_overflow_policy::block)
            : logger(std::move(logger_name), begin, end), thread_pool_(std::move(tp)), overflow_policy_(overflow_policy)
        {
        }
 
        async_logger(std::string logger_name, sinks_init_list sinks_list, std::weak_ptr<details::thread_pool> tp, async_overflow_policy overflow_policy = async_overflow_policy::block);
 
        async_logger(std::string logger_name, sink_ptr single_sink, std::weak_ptr<details::thread_pool> tp, async_overflow_policy overflow_policy = async_overflow_policy::block);
 
        std::shared_ptr<logger> clone(std::string new_name) override;
 
    protected:
        void sink_it_(const details::log_msg& msg) override;
        void flush_() override;
        void backend_sink_it_(const details::log_msg& incoming_log_msg);
        void backend_flush_();
 
    private:
        std::weak_ptr<details::thread_pool> thread_pool_;
        async_overflow_policy               overflow_policy_;
    };
} // namespace spdlog
 
#ifdef SPDLOG_HEADER_ONLY
#include "async_logger-inl.h"
#endif