Use blocking queue

example/example.cpp

@@ -28,6 +28,8 @@ int main(int, char *[])
 
     try
     {
+		async_example();
+		return 0;
         auto console = spdlog::stdout_color_st("console");
         console->info("Welcome to spdlog!");
 
@@ -82,7 +84,7 @@ int main(int, char *[])
 
         // Asynchronous logging is very fast..
         // Just call spdlog::set_async_mode(q_size) and all created loggers from now on will be asynchronous..
-        async_example();
+        //async_example();
 
         // Log user-defined types example
         user_defined_example();
@@ -107,15 +109,23 @@ int main(int, char *[])
 #include "spdlog/async.h"
 void async_example()
 {
-    auto async_file = spd::basic_logger_mt<spdlog::create_async>("async_file_logger", "logs/async_log.txt");
-    for (int i = 0; i < 100; ++i)
+    //auto async_file = spd::basic_logger_mt<spdlog::create_async>("async_file_logger", "logs/async_log.txt");
+	
+	for (int j = 0; j < 1; j++)
 	{
-        async_file->info("Async message #{}", i);
+		spdlog::init_thread_pool(1024, 10);
+		auto async_file = spd::stderr_color_mt<spdlog::create_async>("console");
+		for (int i = 0; i < 1024; ++i)
+		{
+			async_file->info("{} Async message #{}", j, i);
 		}
+		spdlog::drop_all();
+	}
+	//std::this_thread::sleep_for(std::chrono::seconds(1));
+		
 
     // you can also modify thread pool settings *before* creating the logger:
-    // spdlog::init_thread_pool(32768, 4); // queue with 32k of pre allocated items and 4 backing threads.
-    // if not called a defaults are: preallocated 8192 queue items and 1 worker thread.
+    // spdlog::init_thread_pool(32768, 4); // queue with max 32k items 4 backing threads.    
 }
 
 // syslog example (linux/osx/freebsd)

include/spdlog/details/async_logger_impl.h

@@ -8,7 +8,7 @@
 // async logger implementation
 // uses a thread pool to perform the actual logging
 
-#include "../details/thread_pool.h"
+#include "spdlog/details/thread_pool.h"
 
 #include <chrono>
 #include <memory>

include/spdlog/details/mpmc_blocking_q.h

@@ -0,0 +1,84 @@
+#pragma once
+
+//
+// Copyright(c) 2018 Gabi Melman.
+// Distributed under the MIT License (http://opensource.org/licenses/MIT)
+//
+
+// async log helper :
+// multi producer-multi consumer blocking queue
+// enqueue(..) - will block until room found to put the new message
+// enqueue_nowait(..) - will return immediatly with false if no room left in the queue
+// dequeue_for(..) - will block until the queue is not empty or timeout passed
+
+#include <condition_variable>
+#include <mutex>
+#include <queue>
+
+namespace spdlog {
+namespace details {
+
+template<typename T>
+class mpmc_bounded_queue
+{
+public:
+    using item_type = T;
+    explicit mpmc_bounded_queue(size_t max_items)
+        : max_items_(max_items)
+    {
+    }
+
+    // try to enqueue and block if no room left
+    void enqueue(T &&item)
+    {
+        {
+            std::unique_lock<std::mutex> lock(queue_mutex_);
+            pop_cv_.wait(lock, [this] { return this->q_.size() < this->max_items_; });
+            q_.push(std::move(item));
+        }
+        push_cv_.notify_one();
+    }
+
+    // try to enqueue and return immdeialty false if no room left
+    bool enqueue_nowait(T &&item)
+    {
+        {
+            std::unique_lock<std::mutex> lock(queue_mutex_);
+            if (q_.size() == this->max_items_)
+            {
+                return false;
+            }
+            q_.push(std::forward<T>(item));
+        }
+        push_cv_.notify_one();
+        return true;
+    }
+
+    // try to dequeue item. if no item found. wait upto timeout and try again
+    // Return true, if succeeded dequeue item, false otherwise
+    bool dequeue_for(T &popped_item, std::chrono::milliseconds wait_duration)
+    {
+        {
+            std::unique_lock<std::mutex> lock(queue_mutex_);
+            if (!push_cv_.wait_for(lock, wait_duration, [this] { return this->q_.size() > 0; }))
+            {
+                return false;
+            }
+
+            popped_item = std::move(q_.front());
+            q_.pop();
+        }
+        pop_cv_.notify_one();
+        return true;
+    }
+
+private:
+    size_t max_items_;
+    std::mutex queue_mutex_;
+    std::condition_variable push_cv_;
+    std::condition_variable pop_cv_;
+
+    std::queue<T> q_;
+};
+} // namespace details
+} // namespace spdlog

include/spdlog/details/mpmc_bounded_q.h

@@ -1,183 +0,0 @@
-/*
-A modified version of Bounded MPMC queue by Dmitry Vyukov.
-
-Original code from:
-http://www.1024cores.net/home/lock-free-algorithms/queues/bounded-mpmc-queue
-
-licensed by Dmitry Vyukov under the terms below:
-
-Simplified BSD license
-
-Copyright (c) 2010-2011 Dmitry Vyukov. All rights reserved.
-Redistribution and use in source and binary forms, with or without modification,
-are permitted provided that the following conditions are met:
-1. Redistributions of source code must retain the above copyright notice, this list of
-conditions and the following disclaimer.
-
-2. Redistributions in binary form must reproduce the above copyright notice, this list
-of conditions and the following disclaimer in the documentation and/or other materials
-provided with the distribution.
-
-THIS SOFTWARE IS PROVIDED BY DMITRY VYUKOV "AS IS" AND ANY EXPRESS OR IMPLIED
-WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
-MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
-SHALL DMITRY VYUKOV OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
-INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
-LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA,
-OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
-LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
-OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
-ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-
-The views and conclusions contained in the software and documentation are those of the authors and
-should not be interpreted as representing official policies, either expressed or implied, of Dmitry Vyukov.
-*/
-
-/*
-The code in its current form adds the license below:
-
-Copyright(c) 2015 Gabi Melman.
-Distributed under the MIT License (http://opensource.org/licenses/MIT)
-
-*/
-
-#pragma once
-
-#include "spdlog/common.h"
-
-#include <atomic>
-#include <utility>
-
-namespace spdlog {
-namespace details {
-
-template<typename T>
-class mpmc_bounded_queue
-{
-public:
-    using item_type = T;
-
-    explicit mpmc_bounded_queue(size_t buffer_size)
-        : max_size_(buffer_size)
-        , buffer_(new cell_t[buffer_size])
-        , buffer_mask_(buffer_size - 1)
-    {
-        // queue size must be power of two
-        if (!((buffer_size >= 2) && ((buffer_size & (buffer_size - 1)) == 0)))
-        {
-            throw spdlog_ex("async logger queue size must be power of two");
-        }
-
-        for (size_t i = 0; i != buffer_size; i += 1)
-        {
-            buffer_[i].sequence_.store(i, std::memory_order_relaxed);
-        }
-        enqueue_pos_.store(0, std::memory_order_relaxed);
-        dequeue_pos_.store(0, std::memory_order_relaxed);
-    }
-
-    ~mpmc_bounded_queue()
-    {
-        delete[] buffer_;
-    }
-
-    mpmc_bounded_queue(mpmc_bounded_queue const &) = delete;
-    void operator=(mpmc_bounded_queue const &) = delete;
-
-    bool enqueue(T &&data)
-    {
-        cell_t *cell;
-        size_t pos = enqueue_pos_.load(std::memory_order_relaxed);
-        for (;;)
-        {
-            cell = &buffer_[pos & buffer_mask_];
-            size_t seq = cell->sequence_.load(std::memory_order_acquire);
-            intptr_t dif = static_cast<intptr_t>(seq) - static_cast<intptr_t>(pos);
-            if (dif == 0)
-            {
-                if (enqueue_pos_.compare_exchange_weak(pos, pos + 1, std::memory_order_relaxed))
-                {
-                    break;
-                }
-            }
-            else if (dif < 0)
-            {
-                return false;
-            }
-            else
-            {
-                pos = enqueue_pos_.load(std::memory_order_relaxed);
-            }
-        }
-        cell->data_ = std::move(data);
-        cell->sequence_.store(pos + 1, std::memory_order_release);
-        return true;
-    }
-
-    bool dequeue(T &data)
-    {
-        cell_t *cell;
-        size_t pos = dequeue_pos_.load(std::memory_order_relaxed);
-        for (;;)
-        {
-            cell = &buffer_[pos & buffer_mask_];
-            size_t seq = cell->sequence_.load(std::memory_order_acquire);
-            intptr_t dif = static_cast<intptr_t>(seq) - static_cast<intptr_t>(pos + 1);
-            if (dif == 0)
-            {
-                if (dequeue_pos_.compare_exchange_weak(pos, pos + 1, std::memory_order_relaxed))
-                {
-                    break;
-                }
-            }
-            else if (dif < 0)
-            {
-                return false;
-            }
-            else
-            {
-                pos = dequeue_pos_.load(std::memory_order_relaxed);
-            }
-        }
-        data = std::move(cell->data_);
-        cell->sequence_.store(pos + buffer_mask_ + 1, std::memory_order_release);
-        return true;
-    }
-
-    bool is_empty()
-    {
-        size_t front, front1, back;
-        // try to take a consistent snapshot of front/tail.
-        do
-        {
-            front = enqueue_pos_.load(std::memory_order_acquire);
-            back = dequeue_pos_.load(std::memory_order_acquire);
-            front1 = enqueue_pos_.load(std::memory_order_relaxed);
-        } while (front != front1);
-        return back == front;
-    }
-
-private:
-    struct cell_t
-    {
-        std::atomic<size_t> sequence_;
-        T data_;
-    };
-
-    size_t const max_size_;
-
-    static size_t const cacheline_size = 64;
-    using cacheline_pad_t = char[cacheline_size];
-
-    cacheline_pad_t pad0_;
-    cell_t *const buffer_;
-    size_t const buffer_mask_;
-    cacheline_pad_t pad1_;
-    std::atomic<size_t> enqueue_pos_;
-    cacheline_pad_t pad2_;
-    std::atomic<size_t> dequeue_pos_;
-    cacheline_pad_t pad3_;
-};
-
-} // namespace details
-} // namespace spdlog

include/spdlog/details/thread_pool.h

@@ -1,7 +1,7 @@
 #pragma once
 
 #include "spdlog/details/log_msg.h"
-#include "spdlog/details/mpmc_bounded_q.h"
+#include "spdlog/details/mpmc_blocking_q.h"
 #include "spdlog/details/os.h"
 
 #include <chrono>
@@ -10,21 +10,21 @@
 #include <vector>
 
 namespace spdlog {
-namespace details {
+	namespace details {
 
-using async_logger_ptr = std::shared_ptr<spdlog::async_logger>;
+		using async_logger_ptr = std::shared_ptr<spdlog::async_logger>;
 
-enum class async_msg_type
-{
+		enum class async_msg_type
+		{
 			log,
 			flush,
 			terminate
-};
+		};
 
-// Async msg to move to/from the queue
-// Movable only. should never be copied
-struct async_msg
-{
+		// Async msg to move to/from the queue
+		// Movable only. should never be copied
+		struct async_msg
+		{
 			async_msg_type msg_type;
 			level::level_enum level;
 			log_clock::time_point time;
@@ -37,10 +37,10 @@ struct async_msg
 			async_msg() = default;
 			~async_msg() = default;
 
-    // never copy or assign. should only be move assigned in to the queue..
+			// should only be moved in or out of the queue..
 			async_msg(const async_msg &) = delete;
-    async_msg &operator=(const async_msg &other) = delete;
-    async_msg(async_msg &&other) = delete;
+			async_msg(async_msg &&other) = default;
+			async_msg &operator=(async_msg &&other) = default;
 
 			// construct from log_msg with given type
 			async_msg(async_logger_ptr &&worker, async_msg_type the_type, details::log_msg &&m)
@@ -64,19 +64,6 @@ struct async_msg
 			{
 			}
 
-    // used to move to the message queue
-    async_msg &operator=(async_msg &&other) SPDLOG_NOEXCEPT
-    {
-        msg_type = other.msg_type;
-        level = other.level;
-        time = other.time;
-        thread_id = other.thread_id;
-        raw = std::move(other.raw);
-        msg_id = other.msg_id;
-        worker_ptr = std::move(other.worker_ptr);
-        return *this;
-    }
-
 			// copy into log_msg
 			void to_log_msg(log_msg &&msg)
 			{
@@ -90,17 +77,17 @@ struct async_msg
 				msg.color_range_start = 0;
 				msg.color_range_end = 0;
 			}
-};
+		};
 
-class thread_pool
-{
-public:
+		class thread_pool
+		{
+		public:
 			using item_type = async_msg;
 			using q_type = details::mpmc_bounded_queue<item_type>;
 			using clock_type = std::chrono::steady_clock;
 
 			thread_pool(size_t q_size_bytes, size_t threads_n)
-        : _msg_counter(0)
+				: msg_counter_(0)
 				, _q(q_size_bytes)
 			{
 				// std::cout << "thread_pool()  q_size_bytes: " << q_size_bytes << "\tthreads_n: " << threads_n << std::endl;
@@ -110,7 +97,7 @@ public:
 				}
 				for (size_t i = 0; i < threads_n; i++)
 				{
-            _threads.emplace_back(std::bind(&thread_pool::_worker_loop, this));
+					_threads.emplace_back(std::bind(&thread_pool::worker_loop, this));
 				}
 			}
 
@@ -121,14 +108,14 @@ public:
 				{
 					for (size_t i = 0; i < _threads.size(); i++)
 					{
-                _post_async_msg(async_msg(async_msg_type::terminate), async_overflow_policy::block_retry);
+						post_async_msg(async_msg(async_msg_type::terminate), async_overflow_policy::block_retry);
 					}
 
 					for (auto &t : _threads)
 					{
 						t.join();
 					}
-            // std::cout << "~thread_pool()  _msg_counter: " << _msg_counter << std::endl;
+					// std::cout << "~thread_pool()  msg_counter_: " << msg_counter_ << std::endl;
 				}
 				catch (...)
 				{
@@ -137,106 +124,82 @@ public:
 
 			void post_log(async_logger_ptr &&worker_ptr, details::log_msg &&msg, async_overflow_policy overflow_policy)
 			{
-        async_msg as_m(std::forward<async_logger_ptr>(worker_ptr), async_msg_type::log, std::forward<log_msg>(msg));
-        _post_async_msg(std::move(as_m), overflow_policy);
+				async_msg async_m(std::forward<async_logger_ptr>(worker_ptr), async_msg_type::log, std::forward<log_msg>(msg));
+				post_async_msg(std::move(async_m), overflow_policy);
 			}
 
 			void post_flush(async_logger_ptr &&worker_ptr, async_overflow_policy overflow_policy)
 			{
-        _post_async_msg(async_msg(std::forward<async_logger_ptr>(worker_ptr), async_msg_type::flush), overflow_policy);
+				post_async_msg(async_msg(std::forward<async_logger_ptr>(worker_ptr), async_msg_type::flush), overflow_policy);
 			}
 
 			size_t msg_counter()
 			{
-        return _msg_counter.load(std::memory_order_relaxed);
+				return msg_counter_.load(std::memory_order_relaxed);
 			}
 
-private:
-    std::atomic<size_t> _msg_counter; // total # of messages processed in this pool
+		private:
+			std::atomic<size_t> msg_counter_; // total # of messages processed in this pool
 			q_type _q;
 
 			std::vector<std::thread> _threads;
 
-    void _post_async_msg(async_msg &&new_msg, async_overflow_policy overflow_policy)
+			void post_async_msg(async_msg &&new_msg, async_overflow_policy overflow_policy)
 			{
-
-        if (!_q.enqueue(std::forward<async_msg>(new_msg)) && overflow_policy == async_overflow_policy::block_retry)
+				if (overflow_policy == async_overflow_policy::block_retry)
 				{
-            auto last_op_time = clock_type::now();
-            auto now = last_op_time;
-            do
+					_q.enqueue(std::move(new_msg));
+				}
+				else
 				{
-                now = clock_type::now();
-                sleep_or_yield(now, last_op_time);
-            } while (!_q.enqueue(std::move(new_msg)));
+					_q.enqueue_nowait(std::move(new_msg));
 				}				
 			}
 
-    // pop log messages from the queue and send to the logger worker
-    void _worker_loop()
+			void worker_loop()
 			{
-        async_msg popped_async_msg;
-        log_msg msg;
-        bool active = true;
-        auto last_pop_time = clock_type::now();
-        while (active)
+				while (process_next_msg())
 				{
-            if (_q.dequeue(popped_async_msg))
+				};
+			}
+
+			// process next message in the queue
+			// return true if this thread should still be active (while no terminate msg was received)
+			bool process_next_msg()
 			{
-                last_pop_time = clock_type::now();
-                switch (popped_async_msg.msg_type)
+				async_msg incoming_async_msg;
+				bool dequeued = _q.dequeue_for(incoming_async_msg, std::chrono::seconds(10));
+				if (!dequeued)
+				{
+					return true;
+				}
+
+				switch (incoming_async_msg.msg_type)
 				{
 					case async_msg_type::flush:
 					{
-                    auto worker = std::move(popped_async_msg.worker_ptr);
-                    worker->_backend_flush();
-                    break;
+						incoming_async_msg.worker_ptr->_backend_flush();
+						return true;
 					}
 
 					case async_msg_type::terminate:
-                    active = false;
-                    break;
+					{
+						return false;
+					}
 
 					default:
 					{
-                    popped_async_msg.to_log_msg(std::move(msg));
-                    auto worker = std::move(popped_async_msg.worker_ptr);
-                    worker->_backend_log(msg);
-                    _msg_counter.fetch_add(1, std::memory_order_relaxed);
-                }
-                }
-            }
-            else // queue is empty - the only place we can terminate the thread if needed.
-            {
-                sleep_or_yield(clock_type::now(), last_pop_time);
+						log_msg msg;
+						incoming_async_msg.to_log_msg(std::move(msg));
+						incoming_async_msg.worker_ptr->_backend_log(msg);
+						msg_counter_.fetch_add(1, std::memory_order_relaxed);
+						return true;
 					}
 				}
+				assert(false);
+				return true; // should not be reached
 			}
+		};
 
-    // spin, yield or sleep. use the time passed since last message as a hint
-    static void sleep_or_yield(const clock_type::time_point &now, const clock_type::time_point &last_op_time)
-    {
-        using std::chrono::microseconds;
-        using std::chrono::milliseconds;
-
-        auto time_since_op = now - last_op_time;
-
-        // yield upto 150 micros
-        if (time_since_op <= microseconds(150))
-        {
-            return std::this_thread::yield();
-        }
-
-        // sleep for 20 ms upto 200 ms
-        if (time_since_op <= milliseconds(200))
-        {
-            return details::os::sleep_for_millis(20);
-        }
-
-        // sleep for 500 ms
-        return details::os::sleep_for_millis(500);
-    }
-};
-
-} // namespace details
+	} // namespace details
 } // namespace spdlog

tests/CMakeLists.txt

@@ -7,7 +7,8 @@ set(SPDLOG_UTESTS_SOURCES
     file_helper.cpp
     file_log.cpp
     test_misc.cpp
-	test_pattern_formatter
+	test_pattern_formatter.cpp
+    test_async.cpp
     includes.h
     registry.cpp
     test_macros.cpp

tests/test_async.cpp

@@ -0,0 +1,134 @@
+#include "includes.h"
+#include "test_sink.h"
+#include "spdlog/async.h"
+#include "spdlog/sinks/simple_file_sink.h"
+
+//std::unique_ptr<spdlog::async_logger> create_logger(size_t tp_queue_size, size_t tp_threads)
+//{
+//	auto tp = std::make_shared<details::thread_pool>(8192, 1);
+//	auto logger = std::make_shared<async_logger>("as", test_sink, tp, async_overflow_policy::block_retry);
+//}
+
+TEST_CASE("basic async test ", "[async]")
+{
+	using namespace spdlog;
+	auto test_sink = std::make_shared<sinks::test_sink_mt>();
+	size_t queue_size = 128;
+	size_t messages = 256;
+	{
+		auto tp = std::make_shared<details::thread_pool>(queue_size, 1);
+		auto logger = std::make_shared<async_logger>("as", test_sink, tp, async_overflow_policy::block_retry);
+		for (size_t i = 0; i < messages; i++)
+		{
+			logger->info("Hello message #{}", i);
+		}
+		logger->flush();
+	}
+	REQUIRE(test_sink->msg_counter() == messages);
+	REQUIRE(test_sink->flushed_msg_counter() == messages);
+}
+
+TEST_CASE("discard policy ", "[async]")
+{
+	using namespace spdlog;
+	auto test_sink = std::make_shared<sinks::test_sink_mt>();
+	size_t queue_size = 2;
+	size_t messages = 1024;
+	{
+		auto tp = std::make_shared<details::thread_pool>(queue_size, 1);
+		auto logger = std::make_shared<async_logger>("as", test_sink, tp, async_overflow_policy::discard_log_msg);
+		for (size_t i = 0; i < messages; i++)
+		{
+			logger->info("Hello message #{}", i);
+		}
+	}
+	
+	REQUIRE(test_sink->msg_counter() < messages);
+	REQUIRE(test_sink->flushed_msg_counter() < messages);
+}
+
+TEST_CASE("flush", "[async]")
+{
+	using namespace spdlog;
+	auto test_sink = std::make_shared<sinks::test_sink_mt>();
+	size_t queue_size = 256;
+	size_t messages = 256;
+	{
+		auto tp = std::make_shared<details::thread_pool>(queue_size, 1);
+		auto logger = std::make_shared<async_logger>("as", test_sink, tp, async_overflow_policy::block_retry);
+		for (size_t i = 0; i < messages; i++)
+		{
+			logger->info("Hello message #{}", i);
+		}
+		
+		logger->flush();
+	}
+	std::this_thread::sleep_for(std::chrono::milliseconds(250));
+	REQUIRE(test_sink->msg_counter() == messages);
+	REQUIRE(test_sink->flushed_msg_counter() == messages);	
+}
+
+TEST_CASE("multi threads", "[async]")
+{
+	using namespace spdlog;
+	auto test_sink = std::make_shared<sinks::test_sink_mt>();
+	size_t queue_size = 128;
+	size_t messages = 256;
+	size_t n_threads = 10;
+	{
+		auto tp = std::make_shared<details::thread_pool>(queue_size, 1);
+		auto logger = std::make_shared<async_logger>("as", test_sink, tp, async_overflow_policy::block_retry);
+
+		std::vector<std::thread> threads;
+		for (size_t i = 0; i < n_threads; i++)
+		{
+			threads.emplace_back([logger, messages] {
+				for (size_t j = 0; j < messages; j++)
+				{
+					logger->info("Hello message #{}", j);
+				}
+				
+			});
+		}
+		
+		for (auto &t : threads)
+		{
+			t.join();
+		}
+		logger->flush();
+
+	}
+		
+	REQUIRE(test_sink->msg_counter() == messages * n_threads);
+	REQUIRE(test_sink->flushed_msg_counter() == messages * n_threads);
+}
+
+TEST_CASE("to_file", "[async]")
+{
+	prepare_logdir();
+	size_t queue_size = 512;
+	size_t messages = 512;
+	size_t n_threads = 4;	
+	spdlog::init_thread_pool(queue_size, n_threads);
+	auto logger= spdlog::basic_logger_mt<spdlog::create_async>("as", "logs/async_test.log", true);
+	
+	std::vector<std::thread> threads;
+	for (size_t i = 0; i < n_threads; i++)
+	{
+		threads.emplace_back([logger, messages] {
+			for (size_t j = 0; j < messages; j++)
+			{
+				logger->info("Hello message #{}", j);
+			}
+		});
+	}
+
+	for (auto &t : threads)
+	{
+		t.join();
+	}	
+	logger.reset();
+	spdlog::drop("as");
+	std::this_thread::sleep_for(std::chrono::seconds(1));
+	REQUIRE(count_lines("logs/async_test.log") == messages * n_threads);
+}

tests/test_sink.h

@@ -0,0 +1,48 @@
+//
+// Copyright(c) 2018 Gabi Melman.
+// Distributed under the MIT License (http://opensource.org/licenses/MIT)
+//
+
+#pragma once
+
+#include "spdlog/details/null_mutex.h"
+#include "spdlog/sinks/base_sink.h"
+
+#include <mutex>
+
+namespace spdlog {
+namespace sinks {
+
+template<class Mutex>
+class test_sink : public base_sink<Mutex>
+{
+public:
+    size_t msg_counter()
+    {
+        return msg_counter_;
+    }
+
+    size_t flushed_msg_counter()
+    {
+        return flushed_msg_counter_;
+    }
+
+protected:
+    void _sink_it(const details::log_msg &) override
+    {
+        msg_counter_++;
+    }
+
+    void _flush() override
+    {
+        flushed_msg_counter_ += msg_counter_;
+    }
+    size_t msg_counter_{0};
+    size_t flushed_msg_counter_{0};
+};
+
+using test_sink_mt = test_sink<std::mutex>;
+using test_sink_st = test_sink<details::null_mutex>;
+
+} // namespace sinks
+} // namespace spdlog

tests/tests.vcxproj

@@ -129,6 +129,7 @@
     <ClCompile Include="errors.cpp" />
     <ClCompile Include="file_helper.cpp" />
     <ClCompile Include="file_log.cpp" />
+    <ClCompile Include="test_async.cpp" />
     <ClCompile Include="test_misc.cpp" />
     <ClCompile Include="main.cpp" />
     <ClCompile Include="registry.cpp" />

tests/tests.vcxproj.filters

@@ -42,6 +42,9 @@
     <ClCompile Include="test_misc.cpp">
       <Filter>Source Files</Filter>
     </ClCompile>
+    <ClCompile Include="test_async.cpp">
+      <Filter>Source Files</Filter>
+    </ClCompile>
   </ItemGroup>
   <ItemGroup>
     <ClInclude Include="includes.h">