systemd_sink.h

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// Copyright(c) 2019 ZVYAGIN.Alexander@gmail.com
// Distributed under the MIT License (http://opensource.org/licenses/MIT)
 
#pragma once
 
#include <spdlog/sinks/base_sink.h>
#include <spdlog/details/os.h>
#include <spdlog/details/null_mutex.h>
#include <spdlog/details/synchronous_factory.h>
 
#include <array>
#ifndef SD_JOURNAL_SUPPRESS_LOCATION
#define SD_JOURNAL_SUPPRESS_LOCATION
#endif
#include <systemd/sd-journal.h>
 
namespace spdlog
{
    namespace sinks
    {
 
        template <typename Mutex>
        class systemd_sink : public base_sink<Mutex>
        {
        public:
            systemd_sink(std::string ident = "", bool enable_formatting = false)
                : ident_{std::move(ident)}, enable_formatting_{enable_formatting}, syslog_levels_{{/* spdlog::level::trace      */ LOG_DEBUG,
                                                                                                   /* spdlog::level::debug      */ LOG_DEBUG,
                                                                                                   /* spdlog::level::info       */ LOG_INFO,
                                                                                                   /* spdlog::level::warn       */ LOG_WARNING,
                                                                                                   /* spdlog::level::err        */ LOG_ERR,
                                                                                                   /* spdlog::level::critical   */ LOG_CRIT,
                                                                                                   /* spdlog::level::off        */ LOG_INFO}}
            {
            }
 
            ~systemd_sink() override
            {
            }
 
            systemd_sink(const systemd_sink&)            = delete;
            systemd_sink& operator=(const systemd_sink&) = delete;
 
        protected:
            const std::string ident_;
            bool              enable_formatting_ = false;
            using levels_array                   = std::array<int, 7>;
            levels_array syslog_levels_;
 
            void sink_it_(const details::log_msg& msg) override
            {
                int           err;
                string_view_t payload;
                memory_buf_t  formatted;
                if (enable_formatting_)
                {
                    base_sink<Mutex>::formatter_->format(msg, formatted);
                    payload = string_view_t(formatted.data(), formatted.size());
                }
                else
                {
                    payload = msg.payload;
                }
 
                size_t length = payload.size();
                // limit to max int
                if (length > static_cast<size_t>(std::numeric_limits<int>::max()))
                {
                    length = static_cast<size_t>(std::numeric_limits<int>::max());
                }
 
                const string_view_t syslog_identifier = ident_.empty() ? msg.logger_name : ident_;
 
                // Do not send source location if not available
                if (msg.source.empty())
                {
                    // Note: function call inside '()' to avoid macro expansion
                    err = (sd_journal_send)("MESSAGE=%.*s", static_cast<int>(length), payload.data(), "PRIORITY=%d", syslog_level(msg.level),
#ifndef SPDLOG_NO_THREAD_ID
                                            "TID=%zu", os::thread_id(),
#endif
                                            "SYSLOG_IDENTIFIER=%.*s", static_cast<int>(syslog_identifier.size()), syslog_identifier.data(), nullptr);
                }
                else
                {
                    err = (sd_journal_send)("MESSAGE=%.*s", static_cast<int>(length), payload.data(), "PRIORITY=%d", syslog_level(msg.level),
#ifndef SPDLOG_NO_THREAD_ID
                                            "TID=%zu", os::thread_id(),
#endif
                                            "SYSLOG_IDENTIFIER=%.*s", static_cast<int>(syslog_identifier.size()), syslog_identifier.data(), "CODE_FILE=%s",
                                            msg.source.filename, "CODE_LINE=%d", msg.source.line, "CODE_FUNC=%s", msg.source.funcname, nullptr);
                }
 
                if (err)
                {
                    throw_spdlog_ex("Failed writing to systemd", errno);
                }
            }
 
            int syslog_level(level::level_enum l)
            {
                return syslog_levels_.at(static_cast<levels_array::size_type>(l));
            }
 
            void flush_() override
            {
            }
        };
 
        using systemd_sink_mt = systemd_sink<std::mutex>;
        using systemd_sink_st = systemd_sink<details::null_mutex>;
    } // namespace sinks
 
    // Create and register a syslog logger
    template <typename Factory = spdlog::synchronous_factory>
    inline std::shared_ptr<logger> systemd_logger_mt(
        const std::string& logger_name, const std::string& ident = "", bool enable_formatting = false)
    {
        return Factory::template create<sinks::systemd_sink_mt>(logger_name, ident, enable_formatting);
    }
 
    template <typename Factory = spdlog::synchronous_factory>
    inline std::shared_ptr<logger> systemd_logger_st(
        const std::string& logger_name, const std::string& ident = "", bool enable_formatting = false)
    {
        return Factory::template create<sinks::systemd_sink_st>(logger_name, ident, enable_formatting);
    }
} // namespace spdlog