spdlog/include/spdlog/sinks/daily_rotating_file_sink.h

//
// Copyright(c) 2015 Gabi Melman.
// Distributed under the MIT License (http://opensource.org/licenses/MIT)
//

#pragma once
#include "spdlog/details/file_helper.h"
#include "spdlog/details/null_mutex.h"
#include "spdlog/fmt/fmt.h"
#include "spdlog/sinks/base_sink.h"
#include "spdlog/spdlog.h"

#include <cerrno>
#include <chrono>
#include <cstdio>
#include <ctime>
#include <mutex>
#include <string>
#include <tuple>


namespace spdlog {
namespace sinks {

/*
 * Generator of daily log file names in format basename.YYYY-MM-DD.ext
 */
struct daily_filename_calculator
{
    // Create filename for the form basename.YYYY-MM-DD
    static filename_t calc_filename(const filename_t &filename, const tm &now_tm)
    {
        filename_t basename, ext;
        std::tie(basename, ext) = details::file_helper::split_by_extenstion(filename);
        std::conditional<std::is_same<filename_t::value_type, char>::value, fmt::memory_buffer, fmt::wmemory_buffer>::type w;
        fmt::format_to(
            w, SPDLOG_FILENAME_T("{}_{:04d}-{:02d}-{:02d}{}"), basename, now_tm.tm_year + 1900, now_tm.tm_mon + 1, now_tm.tm_mday, ext);
        return fmt::to_string(w);
    }
};

/*
 * Rotating file sink based on date. rotates at midnight
 */
template<typename Mutex, typename FileNameCalc = daily_filename_calculator>
class daily_rotating_file_sink final : public base_sink<Mutex>
{
public:
    // create daily file sink which rotates on given time
	daily_rotating_file_sink(filename_t base_filename, std::size_t max_size, int rotation_hour, int rotation_minute, bool truncate = false)
        : base_filename_(std::move(base_filename))
		, max_size_(max_size)
        , rotation_h_(rotation_hour)
        , rotation_m_(rotation_minute)
        , truncate_(truncate)
    {
        if (rotation_hour < 0 || rotation_hour > 23 || rotation_minute < 0 || rotation_minute > 59)
        {
            throw spdlog_ex("daily_file_sink: Invalid rotation time in ctor");
        }
        auto now = log_clock::now();
        file_helper_.open(FileNameCalc::calc_filename(base_filename_, now_tm(now)), truncate_);
        rotation_tp_ = next_rotation_tp_();
		current_size_ = file_helper_.size(); // expensive. called only once
    }

protected:
    void sink_it_(const details::log_msg &msg) override
    {
		today_filename_ = FileNameCalc::calc_filename(base_filename_, now_tm(msg.time));

        if (msg.time >= rotation_tp_)
        {
            file_helper_.open(today_filename_, truncate_);
            rotation_tp_ = next_rotation_tp_();
        }

        fmt::memory_buffer formatted;
        sink::formatter_->format(msg, formatted);

		current_size_ += formatted.size();
		if (current_size_ > max_size_)
		{
			rotate_();
			current_size_ = formatted.size();
		}

        file_helper_.write(formatted);
    }

    void flush_() override
    {
        file_helper_.flush();
    }

private:
    tm now_tm(log_clock::time_point tp)
    {
        time_t tnow = log_clock::to_time_t(tp);
        return spdlog::details::os::localtime(tnow);
    }

    log_clock::time_point next_rotation_tp_()
    {
        auto now = log_clock::now();
        tm date = now_tm(now);
        date.tm_hour = rotation_h_;
        date.tm_min = rotation_m_;
        date.tm_sec = 0;
        auto rotation_time = log_clock::from_time_t(std::mktime(&date));
        if (rotation_time > now)
        {
            return rotation_time;
        }
        return {rotation_time + std::chrono::hours(24)};
    }

	// Rotate files:
	// log.txt -> log.1.txt
	// log.1.txt -> log.2.txt
	// log.2.txt -> log.3.txt
	// log.3.txt -> log.4.txt
	void rotate_()
	{
		using details::os::filename_to_str;
		file_helper_.close();
		for (auto i = max_files_; i >= 0; --i)
		{
			filename_t src = calc_filename(today_filename_, i);
			if (!details::file_helper::file_exists(src))
			{
				continue;
			}
			filename_t target = calc_filename(today_filename_, i + 1);

			if (!rename_file(src, target))
			{
				// if failed try again after a small delay.
				// this is a workaround to a windows issue, where very high rotation
				// rates can cause the rename to fail with permission denied (because of antivirus?).
				details::os::sleep_for_millis(100);
				if (!rename_file(src, target))
				{
					file_helper_.reopen(true); // truncate the log file anyway to prevent it to grow beyond its limit!
					throw spdlog_ex(
						"rotating_file_sink: failed renaming " + filename_to_str(src) + " to " + filename_to_str(target), errno);
				}
			}
		}
		++max_files_;
		file_helper_.reopen(true);
	}

	// delete the target if exists, and rename the src file  to target
	// return true on success, false otherwise.
	bool rename_file(const filename_t &src_filename, const filename_t &target_filename)
	{
		// try to delete the target file in case it already exists.
		(void)details::os::remove(target_filename);
		return details::os::rename(src_filename, target_filename) == 0;
	}

	static filename_t calc_filename(const filename_t &filename, std::size_t index)
	{
		typename std::conditional<std::is_same<filename_t::value_type, char>::value, fmt::memory_buffer, fmt::wmemory_buffer>::type w;
		if (index != 0u)
		{
			filename_t basename, ext;
			std::tie(basename, ext) = details::file_helper::split_by_extenstion(filename);
			fmt::format_to(w, SPDLOG_FILENAME_T("{}.{}{}"), basename, index, ext);
		}
		else
		{
			fmt::format_to(w, SPDLOG_FILENAME_T("{}"), filename);
		}
		return fmt::to_string(w);
	}

	std::size_t max_size_;
	std::size_t max_files_;
	std::size_t current_size_;
	filename_t today_filename_;
    filename_t base_filename_;
    int rotation_h_;
    int rotation_m_;
    log_clock::time_point rotation_tp_;
    details::file_helper file_helper_;
    bool truncate_;
};

using daily_rotating_file_sink_mt = daily_rotating_file_sink<std::mutex>;
using daily_rotating_file_sink_st = daily_rotating_file_sink<details::null_mutex>;

} // namespace sinks

//
// factory functions
//
template<typename Factory = default_factory>
inline std::shared_ptr<logger> daily_rotating_logger_mt(
    const std::string &logger_name, const filename_t &filename, std::size_t max_size, int hour = 0, int minute = 0, bool truncate = false)
{
    return Factory::template create<sinks::daily_rotating_file_sink_mt>(logger_name, filename, max_size, hour, minute, truncate);
}

template<typename Factory = default_factory>
inline std::shared_ptr<logger> daily_rotating_logger_st(
    const std::string &logger_name, const filename_t &filename, std::size_t max_size, int hour = 0, int minute = 0, bool truncate = false)
{
    return Factory::template create<sinks::daily_rotating_file_sink_st>(logger_name, filename, max_size, hour, minute, truncate);
}
} // namespace spdlog