I am a novice about boost::asio, I write a server, some clients can connect to it and keep listening.
class socket_server {
public:
~socket_server() { io_context.stop(); };
int server_process();
private:
boost::asio::io_context io_context;
};
int socket_server::server_process() {
try {
unlink("/var/run/socket");
server s(io_context, "/var/run/socket");
INFO("server_process, start run\n");
io_context.run();
} catch (std::exception &e) {
std::cerr << "Exception: " << e.what() << "\n";
}
return 0;
}
class server {
public:
server(boost::asio::io_context &io_context, const std::string &file)
: acceptor_(io_context, stream_protocol::endpoint(file)), socket_id_(0) {
do_accept();
}
private:
void do_accept();
stream_protocol::acceptor acceptor_;
int socket_id_;
};
void server::do_accept() {
INFO("do accept\n");
acceptor_.async_accept(
[this](std::error_code ec, stream_protocol::socket socket) {
if (!ec) {
INFO("new session create\n");
std::make_shared<session>(std::move(socket), socket_id_++)->start();
}
do_accept();
});
}
class session : public std::enable_shared_from_this<session> {
public:
session(stream_protocol::socket sock, int socket_id)
: socket_(std::move(sock)), socket_id_(socket_id) {}
~session() { socket_id_--; }
void start();
private:
void do_read();
void do_write(std::array<char, 1024> data);
int get_id() { return socket_id_; }
// The socket used to communicate with the client.
stream_protocol::socket socket_;
// Buffer used to store data received from the client.
std::array<char, 1024> data_;
int socket_id_;
};
void session::start() { do_read(); }
void session::do_read() {
INFO("in do_read\n");
auto self(shared_from_this());
socket_.async_read_some(
boost::asio::buffer(data_),
[this, self](std::error_code ec, std::size_t length) {
if (!ec) {
if (request.find("listen") != std::string::npos) {
std::unique_lock<std::mutex> lock(unsol_mutex);
unsol_cond.wait(lock)
do_write(get_unsol_data());
} else {
std::unique_lock<std::mutex> lock(send_mutex);
if (send_cond.wait_for(lock, std::chrono::seconds(2)) ==
std::cv_status::timeout) {
ERROR("response time out\n");
}
do_write(get_write_data());
}
}
});
}
In do_read(), I found when a client is listening (block in unsol_cond.wait(lock)), another client can not go to do_read().
Is it due to make_shared session? Is there a better implementation suggestion?
Thanks~
You're using blocking synchronization primitives in async code. That's an anti-pattern.
Firstly, as you noticed, the blocking operations will prevent the event loop from progressing.
Secondly, holding locks across async calls is often a bug (it doesn't guard the critical execution during execution of the async operation).
For simple integration with Asio proactor model, you can often
use a strand instead.
Under the hood, it will end up using mutexes, just like now, but only
if the concurrency model requires it. That mainly depends on the
execution context used and/or how many threads are running the
services.
Use a queue with a async send-chain. I have quite a few answers on this site that show you how to do that.
I would gladly demonstrate, but the code is too incomplete, and the naming doesn't really give me an idea what things mean ("listen"/"unsol"?, nothing ever signals those conditions so... hard to guess what they do in reality)
Related
Hello, if i try to build this code here, ill get a error and dont know what to do.
void wxsocket_test_finalFrame::OnServerStart(wxCommandEvent& WXUNUSED(event))
{
// Create the address - defaults to localhost:0 initially
wxIPV4address addr;
addr.Service(3000);
// Create the socket. We maintain a class pointer so we can
// shut it down
m_server = new wxSocketServer(addr);
// We use Ok() here to see if the server is really listening
if (! m_server->Ok())
{
return;
}
// Set up the event handler and subscribe to connection events
m_server->SetEventHandler(*this, SERVER_ID);
m_server->SetNotify(wxSOCKET_CONNECTION_FLAG);
m_server->Notify(true);
}
void wxsocket_test_finalFrame::OnServerEvent(wxSocketEvent& WXUNUSED(event))
{
// Accept the new connection and get the socket pointer
wxSocketBase* sock = m_server->Accept(false);
// Tell the new socket how and where to process its events
sock->SetEventHandler(*this, SOCKET_ID);
sock->SetNotify(wxSOCKET_INPUT_FLAG | wxSOCKET_LOST_FLAG);
sock->Notify(true);
}
void wxsocket_test_finalFrame::OnSocketEvent(wxSocketEvent& event)
{
wxSocketBase *sock = event.GetSocket();
// Process the event
switch(event.GetSocketEvent())
{
case wxSOCKET_INPUT:
{
char buf[10];
// Read the data
sock->Read(buf, sizeof(buf));
// Write it back
sock->Write(buf, sizeof(buf));
// We are done with the socket, destroy it
sock->Destroy();
break;
}
case wxSOCKET_LOST:
{
sock->Destroy();
break;
}
}
}
\wxsocket_test_finalMain.cpp|99|error: 'm_server' was not declared in this scope|
OS: Windows
Compiler: gcc version 8.1.0 (x86_64-posix-seh-rev0, Built by MinGW-W64 project)
im a bloody newbie and cant figure out what is happening here, someone has a clue ?
I would like to ask if the decorator pattern suits my needs and is another way to make my software design much better?
Previously I have a device which is always on all the time. On the code below, that is the Device class. Now, to conserve some battery life, I need to turn it off then On again. I created a DeviceWithOnOffDecorator class. I used decorator pattern which I think helped a lot in avoiding modifications on the Device class. But having On and Off on every operation, I feel that the code doesn't conform to DRY principle.
namespace Decorator
{
interface IDevice
{
byte[] GetData();
void SendData();
}
class Device : IDevice
{
public byte[] GetData() {return new byte[] {1,2,3 }; }
public void SendData() {Console.WriteLine("Sending Data"); }
}
// new requirement, the device needs to be turned on and turned off
// after each operation to save some Battery Power
class DeviceWithOnOffDecorator:IDevice
{
IDevice mIdevice;
public DeviceWithOnOffDecorator(IDevice d)
{
this.mIdevice = d;
Off();
}
void Off() { Console.WriteLine("Off");}
void On() { Console.WriteLine("On"); }
public byte[] GetData()
{
On();
var b = mIdevice.GetData();
Off();
return b;
}
public void SendData()
{
On();
mIdevice.SendData();
Off();
}
}
class Program
{
static void Main(string[] args)
{
Device device = new Device();
DeviceWithOnOffDecorator devicewithOnOff = new DeviceWithOnOffDecorator(device);
IDevice iDevice = devicewithOnOff;
var data = iDevice.GetData();
iDevice.SendData();
}
}
}
On this example: I just have two operations only GetData and SendData, but on the actual software there are lots of operations involved and I need to do enclose each operations with On and Off,
void AnotherOperation1()
{
On();
// do all stuffs here
Off();
}
byte AnotherOperation2()
{
On();
byte b;
// do all stuffs here
Off();
return b;
}
I feel that enclosing each function with On and Off is repetitive and is there a way to improve this?
Edit: Also, the original code is in C++. I just wrote it in C# here to be able to show the problem clearer.
Decorator won't suite this purpose, since you are not adding the responsibility dynamically. To me what you need to do is intercept the request and execute on() and off() methods before and after the actual invocation. For that purpose write a Proxy that wraps the underlying instance and do the interception there while leaving your original type as it is.
Trying to simulate scenario for heavy load with Redis (default config only).
To keep it simple, when multi is issued immediately excute then close the connection.
import io.vertx.core.*;
import io.vertx.core.json.Json;
import io.vertx.redis.RedisClient;
import io.vertx.redis.RedisOptions;
import io.vertx.redis.RedisTransaction;
class MyVerticle extends AbstractVerticle {
private int index;
public MyVerticle(int index) {
this.index = index;
}
private void run2() {
RedisClient client = RedisClient.create(vertx, new RedisOptions().setHost("127.0.0.1"));
RedisTransaction tr = client.transaction();
tr.multi(ev2 -> {
if (ev2.succeeded()) {
tr.exec(ev3 -> {
if (ev3.succeeded()) {
tr.close(i -> {
if (i.failed()) {
System.out.println("FAIL TR CLOSE");
client.close(j -> {
if (j.failed()) {
System.out.println("FAIL CLOSE");
}
});
}
});
}
else {
System.out.println("FAIL EXEC");
tr.close(i -> {
if (i.failed()) {
System.out.println("FAIL TR CLOSE");
client.close(j -> {
if (j.failed()) {
System.out.println("FAIL CLOSE");
}
});
}
});
}
});
}
else {
System.out.println("FAIL MULTI");
tr.close(i -> {
if (i.failed()) {
client.close(j -> {
if (j.failed()) {
System.out.println("FAIL CLOSE");
}
});
}
});
}
});
}
#Override
public void start(Future<Void> startFuture) {
long timerID = vertx.setPeriodic(1, new Handler<Long>() {
public void handle(Long aLong) {
run2();
}
});
}
#Override
public void stop(Future stopFuture) throws Exception {
System.out.println("MyVerticle stopped!");
}
}
public class Periodic {
public static void main(String[] args) {
Vertx vertx = Vertx.vertx();
for (int i = 0; i < 8000; i++) {
vertx.deployVerticle(new MyVerticle(i));
}
}
}
Although connections are closed properly I still get warning errors.
All of them are thrown even before I put more logic within multi.
2017-06-20 16:29:49 WARNING io.netty.util.concurrent.DefaultPromise notifyListener0 An exception was thrown by io.vertx.core.net.impl.ChannelProvider$$Lambda$61/1899599620.operationComplete()
java.lang.IllegalStateException: Uh oh! Event loop context executing with wrong thread! Expected null got Thread[globalEventExecutor-1-2,5,main]
at io.vertx.core.impl.ContextImpl.lambda$wrapTask$2(ContextImpl.java:316)
at io.vertx.core.impl.ContextImpl.executeFromIO(ContextImpl.java:193)
at io.vertx.core.net.impl.NetClientImpl.failed(NetClientImpl.java:258)
at io.vertx.core.net.impl.NetClientImpl.lambda$connect$5(NetClientImpl.java:233)
at io.vertx.core.net.impl.ChannelProvider.lambda$connect$0(ChannelProvider.java:42)
at io.netty.util.concurrent.DefaultPromise.notifyListener0(DefaultPromise.java:507)
at io.netty.util.concurrent.DefaultPromise.notifyListenersNow(DefaultPromise.java:481)
at io.netty.util.concurrent.DefaultPromise.access$000(DefaultPromise.java:34)
at io.netty.util.concurrent.DefaultPromise$1.run(DefaultPromise.java:431)
at io.netty.util.concurrent.GlobalEventExecutor$TaskRunner.run(GlobalEventExecutor.java:233)
at io.netty.util.concurrent.DefaultThreadFactory$DefaultRunnableDecorator.run(DefaultThreadFactory.java:144)
at java.lang.Thread.run(Thread.java:745)
Is there a reason for this error ?
You'll continue to get errors, because you test the wrong things.
First of all, vertices are not fat coroutines. They are thin actors. Meaning creating 500 of them won't speed things up, but probably will slow everything down, because event loop still needs to switch between them.
Second, if you want to prepare for 2K concurrent requests, put your Vertx application on one machine, and run wrk or similar tool over the network.
Third, your Redis is also on the same machine. I hope that won't be the case in your production, since Redis will compete with Vertx over CPU.
Once everything is setup correctly, I believe that you'll be able to handle 10K requests quite easily. I've seen Vertx handle 8K requests on modest machines with PostgreSQL.
I'm trying to write a SSL-based async server using Boost ASIO example code from here.
I get the first message and its response correctly at the client side. Then, I send a second message which is received fine at the server, however when the response is sent to client. It comes as some gibberish.
I have uploaded the server code to pastebin. Also, find it below:
// file - Server.h
class Server
{
public:
explicit Server(const std::string &address,
int port,
std::size_t threadPoolSize);
// run the io_service loop
void run();
// stop the server
void stop();
private:
//handle async accept operation
void handleAccept(const boost::system::error_code &e);
// number of threads in thread pool
std::size_t _threadPoolSize;
// the io_service
boost::asio::io_service _ioService;
// acceptor to listen for incoming connections
boost::asio::ip::tcp::acceptor _acceptor;
std::string get_password()
{
return "password";
}
// ssl context
boost::asio::ssl::context _context;
ConnectionPtr _connection;
};
//////////////////////////////////////////////////////////////////////////
// file - Server.cpp
//////////////////////////////////////////////////////////////////////////
Server::Server(const std::string& address,
int port,
std::size_t threadPoolSize)
: _threadPoolSize(threadPoolSize),
_acceptor(_ioService),
_context(_ioService, boost::asio::ssl::context::sslv23),
_connection()
{
try {
DEBUG_2("Starting server on port: ", port);
boost::asio::ip::tcp::endpoint endpoint(boost::asio::ip::tcp::v4(), port);
_acceptor.open(endpoint.protocol());
_acceptor.set_option(boost::asio::ip::tcp::acceptor::reuse_address(true));
_acceptor.bind(endpoint);
_acceptor.listen();
_context.set_options(
boost::asio::ssl::context::default_workarounds
| boost::asio::ssl::context::no_sslv2
| boost::asio::ssl::context::single_dh_use);
_context.set_password_callback(boost::bind(&Server::get_password, this));
_context.use_certificate_chain_file("./demoCA/cacert.pem");
_context.use_private_key_file("./demoCA/private/cakey.pem",
boost::asio::ssl::context::pem);
// _context.use_tmp_dh_file("dh512.pem");
_connection.reset(new CclConnection(_ioService, _context));
_acceptor.async_accept(_connection->socket(),
boost::bind(&Server::handleAccept,
this,
boost::asio::placeholders::error));
}
catch(std::exception& e)
{
STD_EXCEPTION_MESSAGE;
throw;
}
}
void Server::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 < _threadPoolSize; ++i)
{
boost::shared_ptr<boost::thread>
thread(new boost::thread(
boost::bind(&boost::asio::io_service::run,
&_ioService)
)
);
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 Server::stop()
{
_ioService.stop();
}
void Server::handleAccept(const boost::system::error_code& e)
{
if (!e)
{
_connection->handshake();
_connection.reset(new CclConnection(_ioService, _context));
_acceptor.async_accept(_connection->socket(),
boost::bind(&Server::handleAccept,
this,
boost::asio::placeholders::error));
}
}
////////////////////////////////////////////////////////////
// file - Connection.h
////////////////////////////////////////////////////////////
#include <boost/asio.hpp>
#include <boost/asio/ssl.hpp>
#include <boost/shared_ptr.hpp>
#include <boost/enable_shared_from_this.hpp>
typedef boost::asio::ssl::stream< boost::asio::ip::tcp::socket >
ssl_socket;
class Connection
: public boost::enable_shared_from_this<Connection>
{
public:
explicit Connection(boost::asio::io_service& io_service,
boost::asio::ssl::context& context);
//get socket from the connection
ssl_socket::lowest_layer_type& socket();
// do an SSL handshake
void handshake();
//get socket from the connection
boost::asio::io_service::strand& strand();
// start first async operation
void start();
void sendResponse(const Response& response);
void close();
// get remote IP address for this connection
std::string getIPAddress();
private:
void handleRead(const boost::system::error_code& e,
std::size_t bytesTransferred);
void handleWrite(const boost::system::error_code& e);
boost::asio::io_service::strand _strand;
ssl_socket _socket;
void handleHandshake(const boost::system::error_code& e);
boost::array<char, 8192> _buffer;
};
typedef boost::shared_ptr<Connection> ConnectionPtr;
///////////////////////////////////////////////////////////////
// File - Connection.cpp
///////////////////////////////////////////////////////////////
Connection::Connection(boost::asio::io_service& io_service,
boost::asio::ssl::context& context)
: _strand(io_service),
_socket(io_service, context)
{
}
ssl_socket::lowest_layer_type& Connection::socket()
{
return _socket.lowest_layer();
}
boost::asio::io_service::strand& Connection::strand()
{
return _strand;
}
void Connection::start()
{
_socket.async_read_some(boost::asio::buffer(_buffer),
_strand.wrap(
boost::bind(
&Connection::handleRead,
shared_from_this(),
boost::asio::placeholders::error,
boost::asio::placeholders::bytes_transferred
)
)
);
}
void Connection::handshake()
{
std::cout << "doing ssl handshake" << std::endl;
_socket.async_handshake(boost::asio::ssl::stream_base::server,
_strand.wrap(
boost::bind(
&Connection::handleHandshake,
shared_from_this(),
boost::asio::placeholders::error
)
)
);
}
void Connection::handleHandshake(const boost::system::error_code& error)
{
if (!error)
{
_socket.async_read_some(boost::asio::buffer(_buffer),
_strand.wrap(
boost::bind(
&Connection::handleRead,
shared_from_this(),
boost::asio::placeholders::error,
boost::asio::placeholders::bytes_transferred
)
)
);
}
else
{
std::cout << "error occured: " << error.message();
this->close();
}
}
void Connection::handleRead(const boost::system::error_code& e,
std::size_t bytesTransferred)
{
if (!e) {
// handle read data
this->start();
}
else {
this->close();
}
}
void Connection::handleWrite(const boost::system::error_code& e)
{
if (!e) {
this->start();
}
else {
this->close();
}
}
void Connection::sendResponse(const Response& response)
{
boost::asio::async_write(_socket,
boost::asio::buffer(convertToString(response)),
_strand.wrap(
boost::bind(
&Connection::handleWrite,
shared_from_this(),
boost::asio::placeholders::error
)
)
);
}
void Connection::close()
{
boost::system::error_code ignoredCode;
socket().shutdown(boost::asio::ip::tcp::socket::shutdown_both,
ignoredCode);
}
std::string Connection::getIPAddress()
{
return socket().remote_endpoint().address().to_string();
}
Can someone point me out as to what is being done wrongly here?
Update: The issue is resolved as noted by me in the comment. The issue was exactly similar to another old question on stackoverflow.
Your code doesn't recognize, that boost::asio::buffer is only the wrapper for objects from which it was constructed.
Here (in Connection::sendResponse):
boost::asio::buffer(convertToString(response))
You created buffer out of a (probably) temporary object, which was destroyed before it was used by boost::asio::async_write.
Boost.Asio documentation specifically tells you about that in the paragraph "Buffer invalidation"
For the boost::asio::buffer overloads that accept an argument of type
std::string, the buffer objects returned are invalidated according to
the rules defined for invalidation of references, pointers and
iterators referring to elements of the sequence (C++ Std, 21.3).
This question could be a bit difficult to find the answer. It's a questions in one series with What is the reason that Policy.getPolicy() is considered as it will retain a static reference to the context and can cause memory leak. You can read it so you may know more background.
Graped the source code from org.apache.cxf.common.logging.JDKBugHacks and also from org.apache.catalina.core.JreMemoryLeakPreventionListener.
There is a piece of code. Here it is.
URL url = new URL("jar:file://dummy.jar!/");
URLConnection uConn = new URLConnection(url) {
#Override
public void connect() throws IOException{
// NOOP
}
};
uConn.setDefaultUseCaches(false);
The comment said
/*
* Several components end up opening JarURLConnections without
* first disabling caching. This effectively locks the file.
* Whilst more noticeable and harder to ignore on Windows, it
* affects all operating systems.
*
* Those libraries/components known to trigger this issue
* include:
* - log4j versions 1.2.15 and earlier
* - javax.xml.bind.JAXBContext.newInstance()
*/
However I can hardly understand it. Why did they eagerly call setDefaultUseCaches(false) and why on Windows it's harmful that by default cache is true? I cannot find any clue in java.net.JarURLConnection.
I myself find an answer. Any one can correct me if you think I am wrong.
in sun.net.www.protocol.jar.JarURLConnection. I assume this is the default implementation of java.net.JarURLConnection. There is a piece of code below.
If cache is set to true, then it will not close the JarFile's connection. Which means it is locked.
class JarURLInputStream extends java.io.FilterInputStream {
JarURLInputStream (InputStream src) {
super (src);
}
public void close () throws IOException {
try {
super.close();
} finally {
if (!getUseCaches()) {
jarFile.close(); //will not close
}
}
}
}
public void connect() throws IOException {
if (!connected) {
/* the factory call will do the security checks */
jarFile = factory.get(getJarFileURL(), getUseCaches());
/* we also ask the factory the permission that was required
* to get the jarFile, and set it as our permission.
*/
if (getUseCaches()) {
jarFileURLConnection = factory.getConnection(jarFile);
}
if ((entryName != null)) {
jarEntry = (JarEntry)jarFile.getEntry(entryName);
if (jarEntry == null) {
try {
if (!getUseCaches()) {
jarFile.close(); //will not close
}
} catch (Exception e) {
}
throw new FileNotFoundException("JAR entry " + entryName +
" not found in " +
jarFile.getName());
}
}
connected = true;
}
}