scylla/reactor.cc

/*
 * reactor.cc
 *
 *  Created on: Aug 1, 2014
 *      Author: avi
 */

#include "reactor.hh"
#include <cassert>
#include <unistd.h>
#include <fcntl.h>
#include <sys/eventfd.h>

reactor::reactor()
    : _epollfd(epoll_create1(EPOLL_CLOEXEC))
    , _io_eventfd(eventfd(0, EFD_CLOEXEC | EFD_NONBLOCK))
    , _io_eventfd_state(_io_eventfd)
    , _io_context_available(max_aio) {
    assert(_epollfd != -1);
    assert(_io_eventfd != -1);
    auto r = ::io_setup(max_aio, &_io_context);
    assert(r >= 0);
    readable(_io_eventfd_state).then([this] {
        process_io();
    });
}

reactor::~reactor() {
    ::close(_epollfd);
}

future<> reactor::get_epoll_future(pollable_fd_state& pfd,
        promise<> pollable_fd_state::*pr, int event) {
    if (pfd.events_known & event) {
        pfd.events_known &= ~event;
        return make_ready_future();
    }
    pfd.events_requested |= event;
    if (!(pfd.events_epoll & event)) {
        auto ctl = pfd.events_epoll ? EPOLL_CTL_MOD : EPOLL_CTL_ADD;
        pfd.events_epoll |= event;
        ::epoll_event eevt;
        eevt.events = pfd.events_epoll;
        eevt.data.ptr = &pfd;
        int r = ::epoll_ctl(_epollfd, ctl, pfd.fd, &eevt);
        assert(r == 0);
    }
    pfd.*pr = promise<>();
    return (pfd.*pr).get_future();
}

future<> reactor::readable(pollable_fd_state& fd) {
    return get_epoll_future(fd, &pollable_fd_state::pollin, EPOLLIN);
}

future<> reactor::writeable(pollable_fd_state& fd) {
    return get_epoll_future(fd, &pollable_fd_state::pollout, EPOLLOUT);
}

void reactor::forget(pollable_fd_state& fd) {
    if (fd.events_epoll) {
        ::epoll_ctl(_epollfd, EPOLL_CTL_DEL, fd.fd, nullptr);
    }
}

pollable_fd
reactor::listen(socket_address sa, listen_options opts) {
    int fd = ::socket(sa.u.sa.sa_family, SOCK_STREAM | SOCK_NONBLOCK | SOCK_CLOEXEC, 0);
    assert(fd != -1);
    if (opts.reuse_address) {
        int opt = 1;
        ::setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt));
    }
    int r = ::bind(fd, &sa.u.sa, sizeof(sa.u.sas));
    assert(r != -1);
    ::listen(fd, 100);
    return pollable_fd(fd);
}

void reactor::complete_epoll_event(pollable_fd_state& pfd, promise<> pollable_fd_state::*pr,
        int events, int event) {
    if (pfd.events_requested & events & event) {
        pfd.events_requested &= ~EPOLLIN;
        pfd.events_known &= ~EPOLLIN;
        (pfd.*pr).set_value();
        pfd.*pr = promise<>();
    }
}

template <typename Func>
future<io_event>
reactor::submit_io(Func prepare_io) {
    auto pr = new promise<io_event>;
    auto fut = pr->get_future();
    _io_context_available.wait(1).then([this, pr, prepare_io = std::move(prepare_io)] () mutable {
        iocb io;
        prepare_io(io);
        io.data = pr;
        io_set_eventfd(&io, _io_eventfd);
        iocb* p = &io;
        auto r = ::io_submit(_io_context, 1, &p);
        assert(r == 1);
    });
    return fut;
}

void reactor::process_io()
{
    uint64_t count;
    auto r = ::read(_io_eventfd, &count, sizeof(count));
    assert(r == 8);
    assert(count);
    io_event ev[max_aio];
    auto n = ::io_getevents(_io_context, count, count, ev, NULL);
    assert(n >= 0 && size_t(n) == count);
    for (size_t i = 0; i < size_t(n); ++i) {
        auto pr = reinterpret_cast<promise<io_event>*>(ev[i].data);
        pr->set_value(ev[i]);
        delete pr;
    }
    _io_context_available.signal(n);
    readable(_io_eventfd_state).then([this] {
        process_io();
    });
}

void reactor::run() {
    std::vector<std::unique_ptr<task>> current_tasks;
    while (true) {
        while (!_pending_tasks.empty()) {
            std::swap(_pending_tasks, current_tasks);
            for (auto&& tsk : current_tasks) {
                tsk->run();
                tsk.reset();
            }
            current_tasks.clear();
        }
        std::array<epoll_event, 128> eevt;
        int nr = ::epoll_wait(_epollfd, eevt.data(), eevt.size(), -1);
        assert(nr != -1);
        for (int i = 0; i < nr; ++i) {
            auto& evt = eevt[i];
            auto pfd = reinterpret_cast<pollable_fd_state*>(evt.data.ptr);
            auto events = evt.events & (EPOLLIN | EPOLLOUT);
            std::unique_ptr<task> t_in, t_out;
            pfd->events_known |= events;
            auto events_to_remove = events & ~pfd->events_requested;
            complete_epoll_event(*pfd, &pollable_fd_state::pollin, events, EPOLLIN);
            complete_epoll_event(*pfd, &pollable_fd_state::pollout, events, EPOLLOUT);
            if (events_to_remove) {
                pfd->events_epoll &= ~events_to_remove;
                evt.events = pfd->events_epoll;
                auto op = evt.events ? EPOLL_CTL_MOD : EPOLL_CTL_DEL;
                ::epoll_ctl(_epollfd, op, pfd->fd, &evt);
            }
        }
    }
}

socket_address make_ipv4_address(ipv4_addr addr) {
    socket_address sa;
    sa.u.in.sin_family = AF_INET;
    sa.u.in.sin_port = htons(addr.port);
    std::memcpy(&sa.u.in.sin_addr, addr.host, 4);
    return sa;
}

reactor the_reactor;