Re: [Boost-users] Timeout on read/write using Boost.Asio

Subject: Re: [Boost-users] Timeout on read/write using Boost.Asio
From: Igor R (boost.lists_at_[hidden])
Date: 2012-04-19 04:48:31

> What if I cancel all the async operation, is there any partial data which has been read from or write to socket after the cancelation?
> If partial data has been read from or write to socket, how can I issue both async read/write again?

Right, some data might have been sent/received, and you have to
re-synchronise somehow your client and server. Even if it's possible,
it would be pretty complicated. Besides, cancellation is not quite
portable:
http://www.boost.org/doc/libs/1_49_0/doc/html/boost_asio/reference/basic_stream_socket/cancel/overload1.html
That's why it's usually a bad idea to cancel operations on a socket.
Instead, you can just close the socket and then re-establish
connection from scratch.

> I cancel the read/write on a tcp connection because the current node I connected to may be too busy to response, so I can try another node. I do not want cancel all async request because the other pending operations may finish successfully, the workload on peer node is very heavy instead of failure.

Well, I don't know what you application does, but I'm afraid it's not
the right way to go. First of all, why can't you connect all the
"nodes" you need? Anyway, you should decide for every particular
connection whether it's ok or "faulty" (returned error, takes too much
time, no ping, no heartbeat, etc...): if it's ok - wait for response,
if it's faulty - just close it.