[asio] sync operations with timeout
Hello. I write network library which offers blocking socket operations (connect, read, write, ...) with timeouts, using boost::asio asynchronous operations as implementation. It is actually some sort of wrapper around boost::asio. Implementation does something like this (read, for example): do_read() { timer.async_wait(&handle_timer) socket.async_read(..., handle_read); wait_for_all_handlers(); deal_with_ec(); } handle_timer() { socket.cancel(); } handle_read() { timer.cancel(); } I have one io_service for all the sockets/timers with one thread doing io_service::run(). Code is multithreaded, so many threads run that functions like do_read() simultaneously (for different sockets, of course). I have two questions: 1. How to wait for completion of all handlers? Currently I use shared_ptr with mutex+condvar (for each library call), it works fine, but seems to be too heavy-weight. 2. There is a chance (with small timeouts), that timer expires before async_read() is started, so sock.cancel() is no-op in handle_timer(), and timer will be disabled. Currently, I just ignore this. I can use another mutex (or strand) to protect from this, but it is also heavy-weight.
I write network library which offers blocking socket operations (connect, read, write, ...) with timeouts, using boost::asio asynchronous operations as implementation. It is actually some sort of wrapper around boost::asio. Implementation does something like this (read, for example):
do_read() { timer.async_wait(&handle_timer) socket.async_read(..., handle_read); wait_for_all_handlers(); deal_with_ec(); }
handle_timer() { socket.cancel(); } handle_read() { timer.cancel(); }
I have one io_service for all the sockets/timers with one thread doing io_service::run(). Code is multithreaded, so many threads run that functions like do_read() simultaneously (for different sockets, of course).
I have two questions:
1. How to wait for completion of all handlers? Currently I use shared_ptr with mutex+condvar (for each library call), it works fine, but seems to be too heavy-weight.
2. There is a chance (with small timeouts), that timer expires before async_read() is started, so sock.cancel() is no-op in handle_timer(), and timer will be disabled. Currently, I just ignore this. I can use another mutex (or strand) to protect from this, but it is also heavy-weight.
It probably isn't an answer to your questions, but perhaps you'll find the following approach useful: http://lists.boost.org/Archives/boost/2007/04/120339.php
On Tue, Aug 30, 2011 at 05:03:43PM +0300, Igor R wrote:
I write network library which offers blocking socket operations (connect, read, write, ...) with timeouts, using boost::asio asynchronous operations as implementation. It is actually some sort of wrapper around boost::asio. Implementation does something like this (read, for example):
do_read() { timer.async_wait(&handle_timer) socket.async_read(..., handle_read); wait_for_all_handlers(); deal_with_ec(); }
handle_timer() { socket.cancel(); } handle_read() { timer.cancel(); }
I have one io_service for all the sockets/timers with one thread doing io_service::run(). Code is multithreaded, so many threads run that functions like do_read() simultaneously (for different sockets, of course).
I have two questions:
1. How to wait for completion of all handlers? Currently I use shared_ptr with mutex+condvar (for each library call), it works fine, but seems to be too heavy-weight.
2. There is a chance (with small timeouts), that timer expires before async_read() is started, so sock.cancel() is no-op in handle_timer(), and timer will be disabled. Currently, I just ignore this. I can use another mutex (or strand) to protect from this, but it is also heavy-weight.
It probably isn't an answer to your questions, but perhaps you'll find the following approach useful: http://lists.boost.org/Archives/boost/2007/04/120339.php
I saw that message, but in order to work with multiple threads, that approach requires separate io_service for each socket. Currently, I see no easy (lightweight) way to use boost::asio in synchronous mode with timeouts.
participants (2)
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Gennady Proskurin -
Igor R