Added relay_sink.

include/spdlog/logger.h

@@ -125,6 +125,15 @@ class SPDLOG_API logger {
 
     void log(level::level_enum lvl, string_view_t msg) { log(source_loc{}, lvl, msg); }
 
+    void log_raw(const details::log_msg &log_msg) {
+        bool log_enabled = should_log(log_msg.level);
+        bool traceback_enabled = tracer_.enabled();
+        if (!log_enabled && !traceback_enabled) {
+            return;
+        }
+        log_it_(log_msg, log_enabled, traceback_enabled);
+    }
+
     template <typename... Args>
     void trace(format_string_t<Args...> fmt, Args &&...args) {
         log(level::trace, fmt, std::forward<Args>(args)...);

include/spdlog/sinks/relay_sink.h

@@ -0,0 +1,35 @@
+// Copyright(c) 2015-present, Gabi Melman & spdlog contributors.
+// Distributed under the MIT License (http://opensource.org/licenses/MIT)
+
+#pragma once
+
+//
+// Sink to wrap another logger. This is usefull when consolidating multiple application components
+// with built-in loggers into one app wide logger.
+//
+
+#include <spdlog/sinks/base_sink.h>
+#include <spdlog/logger.h>
+
+namespace spdlog {
+namespace sinks {
+
+template <typename Mutex>
+class relay_sink : public base_sink<Mutex> {
+public:
+    relay_sink(const std::shared_ptr<spdlog::logger>& logger)
+        : m_logger{logger} {}
+
+protected:
+    void sink_it_(const spdlog::details::log_msg& msg) override { m_logger->log_raw(msg); };
+    void flush_() override{};
+
+private:
+    std::shared_ptr<spdlog::logger> m_logger;
+};
+
+using relay_sink_mt = relay_sink<std::mutex>;
+using relay_sink_st = relay_sink<spdlog::details::null_mutex>;
+
+}  // namespace sinks
+}  // namespace spdlog

tests/CMakeLists.txt

@@ -34,6 +34,7 @@ set(SPDLOG_UTESTS_SOURCES
     test_eventlog.cpp
     test_pattern_formatter.cpp
     test_async.cpp
+    test_relay_sink.cpp
     test_registry.cpp
     test_macros.cpp
     utils.cpp

tests/test_relay_sink.cpp

@@ -0,0 +1,19 @@
+#include "includes.h"
+#include "spdlog/sinks/relay_sink.h"
+#include "spdlog/logger.h"
+#include "test_sink.h"
+
+TEST_CASE("relay_sink_test1", "[relay_sink]") {
+    using spdlog::sinks::relay_sink_st;
+    using spdlog::sinks::test_sink_mt;
+
+    auto test_sink = std::make_shared<test_sink_mt>();
+    auto remote_logger = std::make_shared<spdlog::logger>("remote", test_sink);
+    auto relay_sink = std::make_shared<relay_sink_st>(remote_logger);
+
+    for (int i = 0; i < 10; i++) {
+        relay_sink->log(spdlog::details::log_msg{"test", spdlog::level::info, "message1"});
+    }
+
+    REQUIRE(test_sink->msg_counter() == 10);
+}