Everything is handle in a single thread
void GameClient::test()
{
std::cout <<"called test" << std::endl;
m_io_context.post([](){
std::cout << "test" << std::endl;
});
}
void GameClient::calledFromALoop()
{
// Use poll instead of run to avoid blocking
auto count = m_io_context.poll();
std::cout << "polled: " << count << std::endl;
}
I want every async task to be handled in calledFromALoop() function.
It is called from a loop around 50 times per second.
This is the output:
...
polled: 0
polled: 0
polled: 0
called test
polled: 0
polled: 0
polled: 0
...
Can you help me understand why the lambda in post isn't executed ?
This is a minimal example, originally in the test function, I use async_resolve, but I have the same behavior.
I don't want to use run() because I don't want calledFromALoop() to block.
But then I don't really understand when the async function is executed (not the handler).
For example I assume async_resolve need some work to set up the resolution, then some time to perform network operation, then the handler (callback). When do these steps are executed ?
I think the set up is done at the call of async_resolve, then network time, then the callback is called from poll(). Am I right ?
Using run() instead of poll() will block during the network time.
The weird behavior is if I change the position of this line auto count = m_io_context.poll();
like this:
void GameClient::test()
{
std::cout <<"called test" << std::endl;
m_io_context.post([](){
std::cout << "test" << std::endl;
});
m_io_context.poll();
}
void GameClient::calledFromALoop()
{
}
I have called test test as expected !
Sure it does:
#include <boost/asio.hpp>
#include <iostream>
namespace asio = boost::asio;
int main() {
asio::io_context ioc(1);
post(ioc, [] { std::cout << "Hello, world!" << std::endl; });
ioc.poll();
}
Prints
Hello, world!
Like others commented, you might let the service run out of work. You must prevent that or reset() it.
asio::io_context ioc(1);
post(ioc, [] { std::cout << "Hello, world!" << std::endl; });
ioc.poll();
post(ioc, [] { std::cout << "Hello, world!" << std::endl; });
ioc.poll(); // doesn't print anything
However, e.g.:
auto work = make_work_guard(ioc);
post(ioc, [] { std::cout << "Hello, world!" << std::endl; });
ioc.poll();
post(ioc, [] { std::cout << "Hello, world!" << std::endl; });
ioc.poll(); // prints!