spdlog/include/spdlog/sinks/systemd_sink.h

// Copyright(c) 2019 ZVYAGIN.Alexander@gmail.com
// Distributed under the MIT License (http://opensource.org/licenses/MIT)

#pragma once

#include <array>

#include "../details/null_mutex.h"
#include "../details/os.h"
#include "./base_sink.h"
#ifndef SD_JOURNAL_SUPPRESS_LOCATION
    #define SD_JOURNAL_SUPPRESS_LOCATION
#endif
#include <systemd/sd-journal.h>

namespace spdlog {
namespace sinks {

/**
 * Sink that write to systemd journal using the `sd_journal_send()` library call.
 */
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.log_level), "TID=%zu", msg.thread_id, "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.log_level), "TID=%zu", msg.thread_id, "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 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
}  // namespace spdlog