Implement basic I/O engine

lib/base/CMakeLists.txt

@@ -34,6 +34,7 @@ set(base_SOURCES
   filelogger.cpp filelogger.hpp filelogger-ti.hpp
   function.cpp function.hpp function-ti.hpp function-script.cpp functionwrapper.hpp
   initialize.cpp initialize.hpp
+  io-engine.cpp io-engine.hpp
   json.cpp json.hpp json-script.cpp
   lazy-init.hpp
   library.cpp library.hpp

lib/base/io-engine.cpp

@@ -0,0 +1,96 @@
+/******************************************************************************
+ * Icinga 2                                                                   *
+ * Copyright (C) 2012-2018 Icinga Development Team (https://icinga.com/)      *
+ *                                                                            *
+ * This program is free software; you can redistribute it and/or              *
+ * modify it under the terms of the GNU General Public License                *
+ * as published by the Free Software Foundation; either version 2             *
+ * of the License, or (at your option) any later version.                     *
+ *                                                                            *
+ * This program is distributed in the hope that it will be useful,            *
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of             *
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the              *
+ * GNU General Public License for more details.                               *
+ *                                                                            *
+ * You should have received a copy of the GNU General Public License          *
+ * along with this program; if not, write to the Free Software Foundation     *
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.             *
+ ******************************************************************************/
+
+#include "base/exception.hpp"
+#include "base/io-engine.hpp"
+#include "base/lazy-init.hpp"
+#include "base/logger.hpp"
+#include <exception>
+#include <memory>
+#include <thread>
+#include <boost/asio/io_service.hpp>
+#include <boost/asio/spawn.hpp>
+#include <boost/date_time/posix_time/ptime.hpp>
+
+using namespace icinga;
+
+CpuBoundWork::CpuBoundWork(boost::asio::yield_context yc)
+{
+	auto& ioEngine (IoEngine::Get());
+
+	for (;;) {
+		auto availableSlots (ioEngine.m_CpuBoundSemaphore.fetch_sub(1));
+
+		if (availableSlots < 1) {
+			ioEngine.m_CpuBoundSemaphore.fetch_add(1);
+			ioEngine.m_AlreadyExpiredTimer.async_wait(yc);
+			continue;
+		}
+
+		break;
+	}
+}
+
+CpuBoundWork::~CpuBoundWork()
+{
+	IoEngine::Get().m_CpuBoundSemaphore.fetch_add(1);
+}
+
+LazyInit<std::unique_ptr<IoEngine>> IoEngine::m_Instance ([]() { return std::unique_ptr<IoEngine>(new IoEngine()); });
+
+IoEngine& IoEngine::Get()
+{
+	return *m_Instance.Get();
+}
+
+boost::asio::io_service& IoEngine::GetIoService()
+{
+	return m_IoService;
+}
+
+IoEngine::IoEngine() : m_IoService(), m_KeepAlive(m_IoService), m_AlreadyExpiredTimer(m_IoService)
+{
+	m_AlreadyExpiredTimer.expires_at(boost::posix_time::neg_infin);
+
+	auto concurrency (std::thread::hardware_concurrency());
+
+	if (concurrency < 2) {
+		m_CpuBoundSemaphore.store(1);
+	} else {
+		m_CpuBoundSemaphore.store(concurrency - 1u);
+	}
+
+	for (auto i (std::thread::hardware_concurrency()); i; --i) {
+		std::thread(&IoEngine::RunEventLoop, this).detach();
+	}
+}
+
+void IoEngine::RunEventLoop()
+{
+	for (;;) {
+		try {
+			m_IoService.run();
+
+			break;
+		} catch (const std::exception& e) {
+			Log(LogCritical, "IoEngine", "Exception during I/O operation!");
+			Log(LogDebug, "IoEngine") << "Exception during I/O operation: " << DiagnosticInformation(e);
+		}
+	}
+}

lib/base/io-engine.hpp

@@ -0,0 +1,85 @@
+/******************************************************************************
+ * Icinga 2                                                                   *
+ * Copyright (C) 2012-2018 Icinga Development Team (https://icinga.com/)      *
+ *                                                                            *
+ * This program is free software; you can redistribute it and/or              *
+ * modify it under the terms of the GNU General Public License                *
+ * as published by the Free Software Foundation; either version 2             *
+ * of the License, or (at your option) any later version.                     *
+ *                                                                            *
+ * This program is distributed in the hope that it will be useful,            *
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of             *
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the              *
+ * GNU General Public License for more details.                               *
+ *                                                                            *
+ * You should have received a copy of the GNU General Public License          *
+ * along with this program; if not, write to the Free Software Foundation     *
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.             *
+ ******************************************************************************/
+
+#ifndef IO_ENGINE_H
+#define IO_ENGINE_H
+
+/**
+ * Boost.Coroutine2 (the successor of Boost.Coroutine)
+ * (1) doesn't even exist in old Boost versions and
+ * (2) isn't supported by ASIO, yet.
+ */
+#define BOOST_COROUTINES_NO_DEPRECATION_WARNING 1
+
+#include "base/lazy-init.hpp"
+#include <atomic>
+#include <memory>
+#include <boost/asio/deadline_timer.hpp>
+#include <boost/asio/io_service.hpp>
+#include <boost/asio/spawn.hpp>
+
+/**
+ * Scope lock for CPU-bound work done in an I/O thread
+ *
+ * @ingroup base
+ */
+class CpuBoundWork
+{
+public:
+	CpuBoundWork(boost::asio::yield_context yc);
+	CpuBoundWork(const CpuBoundWork&) = delete;
+	CpuBoundWork(CpuBoundWork&&) = delete;
+	CpuBoundWork& operator=(const CpuBoundWork&) = delete;
+	CpuBoundWork& operator=(CpuBoundWork&&) = delete;
+	~CpuBoundWork();
+};
+
+/**
+ * Async I/O engine
+ *
+ * @ingroup base
+ */
+class IoEngine
+{
+	friend CpuBoundWork;
+
+public:
+	IoEngine(const IoEngine&) = delete;
+	IoEngine(IoEngine&&) = delete;
+	IoEngine& operator=(const IoEngine&) = delete;
+	IoEngine& operator=(IoEngine&&) = delete;
+
+	static IoEngine& Get();
+
+	boost::asio::io_service& GetIoService();
+
+private:
+	IoEngine();
+
+	void RunEventLoop();
+
+	static LazyInit<std::unique_ptr<IoEngine>> m_Instance;
+
+	boost::asio::io_service m_IoService;
+	boost::asio::io_service::work m_KeepAlive;
+	boost::asio::deadline_timer m_AlreadyExpiredTimer;
+	std::atomic_uint_fast32_t m_CpuBoundSemaphore;
+};
+
+#endif /* IO_ENGINE_H */