Add tcp_syslog_client_sink

Support for sending messages to remote syslog server over TCP

example/example.cpp

@@ -20,6 +20,7 @@ void user_defined_example();
 void err_handler_example();
 void syslog_example();
 void custom_flags_example();
+void tcp_syslog_client_example();
 
 #include "spdlog/spdlog.h"
 #include "spdlog/cfg/env.h"  // support for loading levels from the environment variable
@@ -292,3 +293,10 @@ void custom_flags_example()
     formatter->add_flag<my_formatter_flag>('*').set_pattern("[%n] [%*] [%^%l%$] %v");
     spdlog::set_formatter(std::move(formatter));
 }
+
+#include "spdlog/sinks/syslog_client_sinks.h"
+void tcp_syslog_client_example()
+{
+    auto syslog_logger = spdlog::tcp_syslog_client_logger_mt("syslog_client", {"127.0.0.1", 514});
+    syslog_logger->warn("This message will be sended to syslog server");
+}

include/spdlog/details/syslog_consts.h

@@ -0,0 +1,51 @@
+// Copyright(c) 2015-present, Gabi Melman & spdlog contributors.
+// Distributed under the MIT License (http://opensource.org/licenses/MIT)
+
+#pragma once
+
+namespace spdlog {
+namespace details {
+
+// https://datatracker.ietf.org/doc/html/rfc5424#section-6.2.1
+struct syslog_consts {
+    enum level {
+        SL_EMERG = 0,
+        SL_ALERT,
+        SL_CRIT,
+        SL_ERR,
+        SL_WARNING,
+        SL_NOTICE,
+        SL_INFO,
+        SL_DEBUG
+    };
+
+    enum facility {
+        SF_KERN = 0,
+        SF_USER,
+        SF_MAIL,
+        SF_DAEMON,
+        SF_AUTH,
+        SF_SYSLOG,
+        SF_LPR,
+        SF_NEWS,
+        SF_UUCP,
+        SF_CRON,
+        SF_AUTHPRIV,
+        SF_FTP,
+        SF_NTP,
+        SF_AUDIT,
+        SF_ALERT,
+        SF_CRON2,
+        SF_LOCAL0,
+        SF_LOCAL1,
+        SF_LOCAL2,
+        SF_LOCAL3,
+        SF_LOCAL4,
+        SF_LOCAL5,
+        SF_LOCAL6,
+        SF_LOCAL7
+    };
+};
+
+} // namespace details
+} // namespace spdlog

include/spdlog/sinks/syslog_client_sinks.h

@@ -0,0 +1,90 @@
+// Copyright(c) 2015-present, Gabi Melman & spdlog contributors.
+// Distributed under the MIT License (http://opensource.org/licenses/MIT)
+
+#pragma once
+
+#include <spdlog/details/fmt_helper.h>
+#include <spdlog/details/syslog_consts.h>
+#include <spdlog/sinks/tcp_sink.h>
+
+namespace spdlog {
+namespace sinks {
+
+/**
+ * Sink that sends messages to remote syslog server over TCP
+ */
+template<typename Mutex>
+class tcp_syslog_client_sink : public spdlog::sinks::tcp_sink<Mutex>
+{
+private:
+    using syslog_facility_t = spdlog::details::syslog_consts::facility;
+public:
+    explicit tcp_syslog_client_sink(tcp_sink_config &&sink_config, syslog_facility_t syslog_facility) 
+        : spdlog::sinks::tcp_sink<Mutex>{std::move(sink_config)}
+        , syslog_levels_{
+              /* spdlog::level::trace    */ spdlog::details::syslog_consts::SL_DEBUG,
+              /* spdlog::level::debug    */ spdlog::details::syslog_consts::SL_DEBUG,
+              /* spdlog::level::info     */ spdlog::details::syslog_consts::SL_INFO,
+              /* spdlog::level::warn     */ spdlog::details::syslog_consts::SL_WARNING,
+              /* spdlog::level::err      */ spdlog::details::syslog_consts::SL_ERR,
+              /* spdlog::level::critical */ spdlog::details::syslog_consts::SL_CRIT,
+              /* spdlog::level::off      */ spdlog::details::syslog_consts::SL_INFO}
+        , syslog_facility_{syslog_facility}
+        {
+
+        }
+protected:
+    void sink_it_(const spdlog::details::log_msg &msg) override
+    {
+        memory_buf_t formatted;
+        base_sink<Mutex>::formatter_->format(msg, formatted);
+
+        // https://datatracker.ietf.org/doc/html/rfc5424#section-6.2.1
+        std::string pri{"<" + std::to_string((syslog_facility_ << 3) + syslog_prio_from_level(msg)) + ">"};
+
+        memory_buf_t syslog_formatted;
+        syslog_formatted.append(pri);
+        syslog_formatted.append(formatted);
+
+        if (!spdlog::sinks::tcp_sink<Mutex>::client_.is_connected())
+        {
+            spdlog::sinks::tcp_sink<Mutex>::client_.connect(
+                spdlog::sinks::tcp_sink<Mutex>::config_.server_host, 
+                spdlog::sinks::tcp_sink<Mutex>::config_.server_port);
+        }
+        spdlog::sinks::tcp_sink<Mutex>::client_.send(syslog_formatted.data(), syslog_formatted.size());
+    }
+private:
+    using levels_array = std::array<int, 7>;
+
+    levels_array      syslog_levels_;
+    syslog_facility_t syslog_facility_;
+
+    int syslog_prio_from_level(const details::log_msg &msg) const
+    {
+        return syslog_levels_.at(static_cast<levels_array::size_type>(msg.level));
+    }
+};
+
+using tcp_syslog_client_sink_mt = tcp_syslog_client_sink<std::mutex>;
+using tcp_syslog_client_sink_st = tcp_syslog_client_sink<spdlog::details::null_mutex>;
+
+} // namespace sinks
+
+template<typename Factory = spdlog::synchronous_factory>
+inline std::shared_ptr<logger> tcp_syslog_client_logger_mt(const std::string &logger_name, 
+    spdlog::sinks::tcp_sink_config sink_config,
+    spdlog::details::syslog_consts::facility syslog_facility = spdlog::details::syslog_consts::facility::SF_USER)
+{
+    return Factory::template create<sinks::tcp_syslog_client_sink_mt>(logger_name, std::move(sink_config), syslog_facility);
+}
+
+template<typename Factory = spdlog::synchronous_factory>
+inline std::shared_ptr<logger> tcp_syslog_client_logger_st(const std::string &logger_name, 
+    spdlog::sinks::tcp_sink_config sink_config,
+    spdlog::details::syslog_consts::facility syslog_facility = spdlog::details::syslog_consts::facility::SF_USER)
+{
+    return Factory::template create<sinks::tcp_syslog_client_sink_st>(logger_name, std::move(sink_config), syslog_facility);
+}
+
+} // namespace spdlog