doc/html/boost_asio/example/http/server2/io_service_pool.cpp

//
// io_service_pool.cpp
// ~~~~~~~~~~~~~~~~~~~
//
// Copyright (c) 2003-2010 Christopher M. Kohlhoff (chris at kohlhoff dot com)
//
// Distributed under the Boost Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
//

#include "server.hpp"
#include <stdexcept>
#include <boost/thread.hpp>
#include <boost/bind.hpp>
#include <boost/shared_ptr.hpp>

namespace http {
	namespace server2 {

		io_service_pool::io_service_pool(std::size_t pool_size)
			: next_io_service_(0)
		{
			if (pool_size == 0)
				throw std::runtime_error("io_service_pool size is 0");

			// Give all the io_services work to do so that their run() functions will not
			// exit until they are explicitly stopped.
			for (std::size_t i = 0; i < pool_size; ++i)
			{
				io_service_ptr io_service(new boost::asio::io_service);
				work_ptr work(new boost::asio::io_service::work(*io_service));
				io_services_.push_back(io_service);
				work_.push_back(work);
			}
		}

		void io_service_pool::run()
		{
			// Create a pool of threads to run all of the io_services.
			std::vector<boost::shared_ptr<boost::thread> > threads;
			for (std::size_t i = 0; i < io_services_.size(); ++i)
			{
				boost::shared_ptr<boost::thread> thread(new boost::thread(
					boost::bind(&boost::asio::io_service::run, io_services_[i])));
				threads.push_back(thread);
			}

			// Wait for all threads in the pool to exit.
			for (std::size_t i = 0; i < threads.size(); ++i)
				threads[i]->join();
		}

		void io_service_pool::stop()
		{
			// Explicitly stop all io_services.
			for (std::size_t i = 0; i < io_services_.size(); ++i)
				io_services_[i]->stop();
		}

		boost::asio::io_service& io_service_pool::get_io_service()
		{
			// Use a round-robin scheme to choose the next io_service to use.
			boost::asio::io_service& io_service = *io_services_[next_io_service_];
			++next_io_service_;
			if (next_io_service_ == io_services_.size())
				next_io_service_ = 0;
			return io_service;
		}

	} // namespace server2
} // namespace http