fastmm::net::Reactor Class Reference

#include <fastmm/net/reactor.hpp>

Public Types
using	TimerCallback = InplaceCallback
	Stored inline (no heap): captures up to InplaceCallback::kCapacity bytes.
using	Task = std::function< void()>
using	EventHook = void(*)(void *ctx)
	Called on the reactor thread after the handler of each I/O event, between one socket's event and the next of the same wait: work that must not wait for the whole batch to be handled (the engine's orders behind a burst of market data, live/venue_slot.cpp) goes here.

Public Member Functions
	Reactor ()
	Reactor (ReactorBackend backend)
	Throws std::runtime_error if the backend (epoll_create1 / io_uring_setup) or the eventfd cannot be created.
	~Reactor ()
	Reactor (const Reactor &)=delete
Reactor &	operator= (const Reactor &)=delete
ReactorBackend	backend () const noexcept
bool	add (int fd, IoHandler &handler, IoEvent events) noexcept
	fd registration (reactor thread only).
bool	modify (int fd, IoHandler &handler, IoEvent events) noexcept
bool	remove (int fd) noexcept
bool	is_registered (int fd) const noexcept
TimerId	add_timer (std::int64_t deadline_ns, TimerCallback cb)
	Timers (reactor thread only).
TimerId	add_timer_after (std::int64_t delay_ns, TimerCallback cb)
bool	cancel_timer (TimerId id) noexcept
std::size_t	active_timers () const noexcept
void	post (Task task)
	Thread-safe: queue a task for the reactor thread and wake it.
void	wake () noexcept
	Thread-safe: interrupt a blocking wait in run_once().
int	wake_fd () const noexcept
	The eventfd wake() writes.
int	run_once (int max_wait_ms)
	One iteration: wait for I/O at most min(next timer, max_wait_ms), dispatch I/O, posted tasks, expired timers.
void	run (const std::atomic< bool > &stop)
	Loop until stop becomes true (checked once per iteration; call wake() after setting it).
void	set_busy_poll (bool enabled) noexcept
	Busy polling: never block, pause instruction between empty polls.
bool	busy_poll () const noexcept
void	set_after_event (EventHook fn, void *ctx) noexcept
bool	event_hangup () const noexcept
	True while a handler runs for an event that also reported a hang-up or an error (RDHUP/HUP/ERR).
int	epoll_fd () const noexcept
	The epoll descriptor, or -1 with the io_uring backend.

Static Public Member Functions
static bool	io_uring_supported () noexcept
	True when this kernel lets the process create an io_uring with everything the backend uses (multishot poll, poll update, EXT_ARG timeouts).
static ReactorBackend	resolve_backend (ReactorBackend requested) noexcept
	requested, or Epoll when io_uring was requested but is not supported.
static std::int64_t	now_ns () noexcept
	CLOCK_MONOTONIC.

Member Typedef Documentation

TimerCallback

using fastmm::net::Reactor::TimerCallback = InplaceCallback

Stored inline (no heap): captures up to InplaceCallback::kCapacity bytes.

Task

using fastmm::net::Reactor::Task = std::function<void()>

EventHook

using fastmm::net::Reactor::EventHook = void (*)(void* ctx)

Called on the reactor thread after the handler of each I/O event, between one socket's event and the next of the same wait: work that must not wait for the whole batch to be handled (the engine's orders behind a burst of market data, live/venue_slot.cpp) goes here.

Null: none.

Constructor & Destructor Documentation

Reactor() [1/3]

fastmm::net::Reactor::Reactor ( )

inline

Reactor() [2/3]

fastmm::net::Reactor::Reactor ( ReactorBackend  backend )

explicit

Throws std::runtime_error if the backend (epoll_create1 / io_uring_setup) or the eventfd cannot be created.

Check io_uring_supported() before asking for IoUring.

~Reactor()

fastmm::net::Reactor::~Reactor

(

)

Reactor() [3/3]

fastmm::net::Reactor::Reactor ( const Reactor &  )

delete

Member Function Documentation

operator=()

Reactor & fastmm::net::Reactor::operator= ( const Reactor &  )

delete

backend()

ReactorBackend fastmm::net::Reactor::backend ( ) const

inlinenoexcept

io_uring_supported()

static bool fastmm::net::Reactor::io_uring_supported ( )

staticnoexcept

True when this kernel lets the process create an io_uring with everything the backend uses (multishot poll, poll update, EXT_ARG timeouts).

Probed once, then cached. False on ENOSYS, EPERM (kernel.io_uring_disabled, seccomp), ENOMEM and kernels older than 5.13.

resolve_backend()

static ReactorBackend fastmm::net::Reactor::resolve_backend ( ReactorBackend  requested )

staticnoexcept

requested, or Epoll when io_uring was requested but is not supported.

add()

bool fastmm::net::Reactor::add ( int  fd, IoHandler &  handler, IoEvent  events  )

noexcept

fd registration (reactor thread only).

Registrations always include RDHUP so half-closes surface as on_readable() (read returns EOF). add() fails for an fd that is already registered, a closed fd and (like epoll) regular files and directories.

modify()

bool fastmm::net::Reactor::modify ( int  fd, IoHandler &  handler, IoEvent  events  )

noexcept

remove()

bool fastmm::net::Reactor::remove ( int  fd )

noexcept

is_registered()

bool fastmm::net::Reactor::is_registered ( int  fd ) const

noexcept

add_timer()

TimerId fastmm::net::Reactor::add_timer	(	std::int64_t	deadline_ns,
		TimerCallback	cb
	)

Timers (reactor thread only).

Deadlines are on the now_ns() clock. Arming a timer allocates only when more timers are live than ever before (slot and heap growth).

add_timer_after()

TimerId fastmm::net::Reactor::add_timer_after ( std::int64_t  delay_ns, TimerCallback  cb  )

inline

cancel_timer()

bool fastmm::net::Reactor::cancel_timer ( TimerId  id )

noexcept

active_timers()

std::size_t fastmm::net::Reactor::active_timers ( ) const

inlinenoexcept

post()

void fastmm::net::Reactor::post

(

Task

task

)

Thread-safe: queue a task for the reactor thread and wake it.

wake()

void fastmm::net::Reactor::wake ( )

noexcept

Thread-safe: interrupt a blocking wait in run_once().

wake_fd()

int fastmm::net::Reactor::wake_fd ( ) const

inlinenoexcept

The eventfd wake() writes.

Another process that holds a duplicate (the gateway passes it to the strategy with SCM_RIGHTS) wakes this reactor by writing 1 to it.

run_once()

int fastmm::net::Reactor::run_once

(

int

max_wait_ms

)

One iteration: wait for I/O at most min(next timer, max_wait_ms), dispatch I/O, posted tasks, expired timers.

max_wait_ms < 0 blocks until something happens. Returns the number of I/O events (epoll) or completions (io_uring) dispatched, or -1 on a wait error other than EINTR. epoll rounds the timer bound up to whole milliseconds; io_uring waits in nanoseconds.

run()

void fastmm::net::Reactor::run

(

const std::atomic< bool > &

stop

)

Loop until stop becomes true (checked once per iteration; call wake() after setting it).

set_busy_poll()

void fastmm::net::Reactor::set_busy_poll ( bool  enabled )

inlinenoexcept

Busy polling: never block, pause instruction between empty polls.

epoll calls epoll_wait with a zero timeout; io_uring reads the completion ring without a system call unless the kernel flags pending work.

busy_poll()

bool fastmm::net::Reactor::busy_poll ( ) const

inlinenoexcept

set_after_event()

void fastmm::net::Reactor::set_after_event ( EventHook  fn, void *  ctx  )

inlinenoexcept

event_hangup()

bool fastmm::net::Reactor::event_hangup ( ) const

inlinenoexcept

True while a handler runs for an event that also reported a hang-up or an error (RDHUP/HUP/ERR).

Only when it is false may a handler take a short read as "socket drained" and skip the read that would return EAGAIN: edge-triggered readiness reports data that arrives later with a new event, but an end of stream already reported has no second event.

now_ns()

static std::int64_t fastmm::net::Reactor::now_ns ( )

staticnoexcept

CLOCK_MONOTONIC.

epoll_fd()

int fastmm::net::Reactor::epoll_fd ( ) const

inlinenoexcept

The epoll descriptor, or -1 with the io_uring backend.