[英]Boost.Asio: Is it a good thing to use a `io_service` per connection/socket?
我想創建一個實現每個連接一個線程模型的應用程序。 但是每個連接必須是可停止的。 我已經嘗試了這個boost.asio示例 , 該示例實現了我想要的阻止版本。 但是經過一番質疑,我發現沒有可靠的方法可以停止該示例的會話。 所以我嘗試實現自己的。 我不得不使用異步功能。 由於我想使一個線程僅管理一個連接,並且無法控制將哪個異步作業應用於哪個線程,因此我決定對每個連接/套接字/線程使用io_service
。
那么這是一個好方法嗎,您知道更好的方法嗎?
我的代碼在這里,因此您可以檢查和檢查它:
#include <boost/asio.hpp>
#include <boost/bind.hpp>
#include <boost/array.hpp>
#include <boost/thread.hpp>
#include <boost/scoped_ptr.hpp>
#include <list>
#include <iostream>
#include <string>
#include <istream>
namespace ba = boost::asio;
namespace bs = boost::system;
namespace b = boost;
typedef ba::ip::tcp::acceptor acceptor_type;
typedef ba::ip::tcp::socket socket_type;
const short PORT = 11235;
class Server;
// A connection has its own io_service and socket
class Connection {
protected:
ba::io_service service;
socket_type sock;
b::thread *thread;
ba::streambuf stream_buffer; // for reading etc
Server *server;
void AsyncReadString() {
ba::async_read_until(
sock,
stream_buffer,
'\0', // null-char is a delimiter
b::bind(&Connection::ReadHandler, this,
ba::placeholders::error,
ba::placeholders::bytes_transferred));
}
void AsyncWriteString(const std::string &s) {
std::string newstr = s + '\0'; // add a null char
ba::async_write(
sock,
ba::buffer(newstr.c_str(), newstr.size()),
b::bind(&Connection::WriteHandler, this,
ba::placeholders::error,
ba::placeholders::bytes_transferred));
}
virtual void Session() {
AsyncReadString();
service.run(); // run at last
}
std::string ExtractString() {
std::istream is(&stream_buffer);
std::string s;
std::getline(is, s, '\0');
return s;
}
virtual void ReadHandler(
const bs::error_code &ec,
std::size_t bytes_transferred) {
if (!ec) {
std::cout << (ExtractString() + "\n");
std::cout.flush();
AsyncReadString(); // read again
}
else {
// do nothing, "this" will be deleted later
}
}
virtual void WriteHandler(
const bs::error_code &ec,
std::size_t bytes_transferred) {
}
public:
Connection(Server *s) :
service(),
sock(service),
server(s),
thread(NULL)
{ }
socket_type& Socket() {
return sock;
}
void Start() {
if (thread) delete thread;
thread = new b::thread(
b::bind(&Connection::Session, this));
}
void Join() {
if (thread) thread->join();
}
void Stop() {
service.stop();
}
void KillMe();
virtual ~Connection() {
}
};
// a server also has its own io_service but it's only used for accepting
class Server {
public:
std::list<Connection*> Connections;
protected:
ba::io_service service;
acceptor_type acc;
b::thread *thread;
virtual void AcceptHandler(const bs::error_code &ec) {
if (!ec) {
Connections.back()->Start();
Connections.push_back(new Connection(this));
acc.async_accept(
Connections.back()->Socket(),
b::bind(&Server::AcceptHandler,
this,
ba::placeholders::error));
}
else {
// do nothing
// since the new session will be deleted
// automatically by the destructor
}
}
virtual void ThreadFunc() {
Connections.push_back(new Connection(this));
acc.async_accept(
Connections.back()->Socket(),
b::bind(&Server::AcceptHandler,
this,
ba::placeholders::error));
service.run();
}
public:
Server():
service(),
acc(service, ba::ip::tcp::endpoint(ba::ip::tcp::v4(), PORT)),
thread(NULL)
{ }
void Start() {
if (thread) delete thread;
thread = new b::thread(
b::bind(&Server::ThreadFunc, this));
}
void Stop() {
service.stop();
}
void Join() {
if (thread) thread->join();
}
void StopAllConnections() {
for (auto c : Connections) {
c->Stop();
}
}
void JoinAllConnections() {
for (auto c : Connections) {
c->Join();
}
}
void KillAllConnections() {
for (auto c : Connections) {
delete c;
}
Connections.clear();
}
void KillConnection(Connection *c) {
Connections.remove(c);
delete c;
}
virtual ~Server() {
delete thread;
// connection should be deleted by the user (?)
}
};
void Connection::KillMe() {
server->KillConnection(this);
}
int main() {
try {
Server s;
s.Start();
std::cin.get(); // wait for enter
s.Stop(); // stop listening first
s.StopAllConnections(); // interrupt ongoing connections
s.Join(); // wait for server, should return immediately
s.JoinAllConnections(); // wait for ongoing connections
s.KillAllConnections(); // destroy connection objects
// at the end of scope, Server will be destroyed
}
catch (std::exception &e) {
std::cerr << "Exception: " << e.what() << std::endl;
return 1;
}
return 0;
}
否。每個連接使用io_service
對象絕對是一種氣味。 尤其是由於您還在專用線程上運行每個連接。
在這一點上,你必須問自己,異步給了你什么? 您可以使所有代碼同步,並具有完全相同的線程數等。
顯然,您希望將連接多路復用到數量更少的服務上。 實際上,有一些明智的模型,例如
具有單個服務線程的單個io_service
(通常很好)。 服務上排隊的任何任務都不會阻塞很長時間,否則延遲會受到影響
單個io_service
,帶有多個執行處理程序的線程。 池中的線程數應足以滿足最大值。 支持的同時執行的CPU密集型任務的數量(或者再次,延遲將開始增加)
每個線程io_service,通常每個邏輯核心一個線程,並具有線程親和性,以便它“粘”在該核心上。 這對於緩存局部性而言可能是理想的
這是一個演示,使用選項1從上方顯示慣用風格:
#include <boost/array.hpp>
#include <boost/asio.hpp>
#include <boost/bind.hpp>
#include <boost/enable_shared_from_this.hpp>
#include <boost/make_shared.hpp>
#include <boost/thread.hpp>
#include <iostream>
#include <istream>
#include <list>
#include <string>
namespace ba = boost::asio;
namespace bs = boost::system;
namespace b = boost;
typedef ba::ip::tcp::acceptor acceptor_type;
typedef ba::ip::tcp::socket socket_type;
const short PORT = 11235;
// A connection has its own io_service and socket
class Connection : public b::enable_shared_from_this<Connection>
{
public:
typedef boost::shared_ptr<Connection> Ptr;
protected:
socket_type sock;
ba::streambuf stream_buffer; // for reading etc
std::string message;
void AsyncReadString() {
std::cout << __PRETTY_FUNCTION__ << "\n";
ba::async_read_until(
sock,
stream_buffer,
'\0', // null-char is a delimiter
b::bind(&Connection::ReadHandler, shared_from_this(),
ba::placeholders::error,
ba::placeholders::bytes_transferred));
}
void AsyncWriteString(const std::string &s) {
std::cout << __PRETTY_FUNCTION__ << "\n";
message = s;
ba::async_write(
sock,
ba::buffer(message.c_str(), message.size()+1),
b::bind(&Connection::WriteHandler, shared_from_this(),
ba::placeholders::error,
ba::placeholders::bytes_transferred));
}
std::string ExtractString() {
std::cout << __PRETTY_FUNCTION__ << "\n";
std::istream is(&stream_buffer);
std::string s;
std::getline(is, s, '\0');
return s;
}
void ReadHandler(
const bs::error_code &ec,
std::size_t bytes_transferred)
{
std::cout << __PRETTY_FUNCTION__ << "\n";
if (!ec) {
std::cout << (ExtractString() + "\n");
std::cout.flush();
AsyncReadString(); // read again
}
else {
// do nothing, "this" will be deleted later
}
}
void WriteHandler(const bs::error_code &ec, std::size_t bytes_transferred) {
std::cout << __PRETTY_FUNCTION__ << "\n";
}
public:
Connection(ba::io_service& svc) : sock(svc) { }
virtual ~Connection() {
std::cout << __PRETTY_FUNCTION__ << "\n";
}
socket_type& Socket() { return sock; }
void Session() { AsyncReadString(); }
void Stop() { sock.cancel(); }
};
// a server also has its own io_service but it's only used for accepting
class Server {
public:
std::list<boost::weak_ptr<Connection> > m_connections;
protected:
ba::io_service _service;
boost::optional<ba::io_service::work> _work;
acceptor_type _acc;
b::thread thread;
void AcceptHandler(const bs::error_code &ec, Connection::Ptr accepted) {
if (!ec) {
accepted->Session();
DoAccept();
}
else {
// do nothing the new session will be deleted automatically by the
// destructor
}
}
void DoAccept() {
auto newaccept = boost::make_shared<Connection>(_service);
_acc.async_accept(
newaccept->Socket(),
b::bind(&Server::AcceptHandler,
this,
ba::placeholders::error,
newaccept
));
}
public:
Server():
_service(),
_work(ba::io_service::work(_service)),
_acc(_service, ba::ip::tcp::endpoint(ba::ip::tcp::v4(), PORT)),
thread(b::bind(&ba::io_service::run, &_service))
{ }
~Server() {
std::cout << __PRETTY_FUNCTION__ << "\n";
Stop();
_work.reset();
if (thread.joinable()) thread.join();
}
void Start() {
std::cout << __PRETTY_FUNCTION__ << "\n";
DoAccept();
}
void Stop() {
std::cout << __PRETTY_FUNCTION__ << "\n";
_acc.cancel();
}
void StopAllConnections() {
std::cout << __PRETTY_FUNCTION__ << "\n";
for (auto c : m_connections) {
if (auto p = c.lock())
p->Stop();
}
}
};
int main() {
try {
Server s;
s.Start();
std::cerr << "Shutdown in 2 seconds...\n";
b::this_thread::sleep_for(b::chrono::seconds(2));
std::cerr << "Stop accepting...\n";
s.Stop();
std::cerr << "Shutdown...\n";
s.StopAllConnections(); // interrupt ongoing connections
} // destructor of Server will join the service thread
catch (std::exception &e) {
std::cerr << __FUNCTION__ << ":" << __LINE__ << "\n";
std::cerr << "Exception: " << e.what() << std::endl;
return 1;
}
std::cerr << "Byebye\n";
}
我將main()
修改為可以運行2秒,而無需用戶干預。 這樣一來,我就可以在Coliru上進行實時演示(當然,這受客戶端進程數量的限制)。
如果您與很多( 很多 )客戶一起運行它,請使用例如
$ time (for a in {1..1000}; do (sleep 1.$RANDOM; echo -e "hello world $RANDOM\\0" | netcat localhost 11235)& done; wait)
您會發現第二個窗口將它們全部處理:
$ ./test | sort | uniq -c | sort -n | tail
Shutdown in 2 seconds...
Shutdown...
Byebye
2 hello world 28214
2 hello world 4554
2 hello world 6216
2 hello world 7864
2 hello world 9966
2 void Server::Stop()
1000 std::string Connection::ExtractString()
1001 virtual Connection::~Connection()
2000 void Connection::AsyncReadString()
2000 void Connection::ReadHandler(const boost::system::error_code&, std::size_t)
如果您真的發瘋了,並在那里籌集了1000
到例如100000
,您將得到類似於以下內容的信息:
sehe@desktop:/tmp$ ./test | sort | uniq -c | sort -n | tail
Shutdown in 2 seconds...
Shutdown...
Byebye
2 hello world 5483
2 hello world 579
2 hello world 5865
2 hello world 938
2 void Server::Stop()
3 hello world 9613
1741 std::string Connection::ExtractString()
1742 virtual Connection::~Connection()
3482 void Connection::AsyncReadString()
3482 void Connection::ReadHandler(const boost::system::error_code&, std::size_t)
在服務器上重復運行2秒。
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