Asio supports programs that utilise the fork()
system call. Provided the program calls
io_context.notify_fork()
at the appropriate times, Asio will recreate any internal file descriptors
(such as the "self-pipe trick" descriptor used for waking up
a reactor). The notification is usually performed as follows:
io_context_.notify_fork(asio::io_context::fork_prepare); if (fork() == 0) { io_context_.notify_fork(asio::io_context::fork_child); ... } else { io_context_.notify_fork(asio::io_context::fork_parent); ... }
User-defined services can also be made fork-aware by overriding the io_context::service::notify_fork()
virtual function.
Note that any file descriptors accessible via Asio's public API (e.g. the
descriptors underlying basic_socket<>
, posix::stream_descriptor
,
etc.) are not altered during a fork. It is the program's responsibility
to manage these as required.
io_context::notify_fork(), io_context::fork_event, io_context::service::notify_fork(), Fork examples.