Boost::Asio : io_service.run() vs poll() or how do I integrate boost::asio in mainloop

Question

I am currently trying to use boost::asio for some simple tcp networking for the first time, and I allready came across something I am not really sure how to deal with. As fa

Answer 1

A drawback is that you'll make a busy loop.

while(true) {
    myIoService.poll()
}

will use 100% cpu. myIoService.run() will use 0% cpu.

myIoService.run_one() might do what you want but it will block if there is nothing for it to do.

Answer 2

A loop like this lets you poll, doesn't busy-wait, and resets as needed. (I'm using the more recent io_context that replaced io_service.)

while (!exitCondition) {
    if (ioContext.stopped()) {
        ioContext.restart();
    }
    if (!ioContext.poll()) {
        if (stuffToDo) {
            doYourStuff();
        } else {
            std::this_thread::sleep_for(std::chrono::milliseconds(3));
        }
    }
}

Answer 3

Using io_service::poll instead of io_service::run is perfectly acceptable. The difference is explained in the documentation

The poll() function may also be used to dispatch ready handlers, but without blocking.

Note that io_service::run will block if there's any work left in the queue

The work class is used to inform the io_service when work starts and finishes. This ensures that the io_service object's run() function will not exit while work is underway, and that it does exit when there is no unfinished work remaining.

whereas io_service::poll does not exhibit this behavior, it just invokes ready handlers. Also note that you will need to invoke io_service::reset on any subsequent invocation to io_service:run or io_service::poll.