Nick Mathewson wrote:
> On Tue, Oct 02, 2007 at 09:35:48AM +0200, Robert Iakobashvili wrote:
> [...]
>> libcurl has developed a good API for its integration with libevent.
>> libcurl project also maintains and develops a very good asynchronous DNS
>> client library, called c-ares (a clone of ares).
>>
>> Could it be a better path to concentrate the community efforts on
>> integration of c-ares and libcurl with libevent and to assist better
>> to applications?
>
> I would love somebody to get c-ares working right with libevent. I
> don't think this is a matter of "concentrating the community efforts",
> however: I think it's a matter of somebody stepping up to contribute
> the right patch to c-ares.
>
> The last time I checked, the main problems preventing c-ares from
> working optimally with libevent were:
> o C-ares had functions to fetch a list of sockets that needed
> to be read and written, but no way to make a callback happen when
> that list changes. This is fine for select() and poll(), but
> Libevent, on the other hand, wants to be told about _changes_ in
> socket state via event_add and event_del.
>
> Fixing this is probably a matter of adding a callback facility to
> c-ares.
It already exists:
struct ares_options options;
...
options.sock_state_cb = foo;
...
... = ares_init_options(..., &options, ...|ARES_OPT_SOCK_STATE_CB);
> o The only way to tell c-ares about readable/writable sockets was
> via a function, ares_process(), that took an fd_set. This is
> suboptimal because 1) Libevent wants to alert applications about
> one socket at a time, and 2) Libevent is designed for situations
> where there are thousands of sockets, and making an fd_set with
> thousands of elements gives awful performance.
>
> Fixing this is probably a matter of adding an alternate way to
> invoke functionality of ares_process().
Also exists:
void ares_process_fd(ares_channel channel, ares_socket_t read_fd,
ares_socket_t write_fd);
>
> Of course, stuff may have changed since then; these problems may be
> solved.
Yup.
>
> (I, _personally_, don't think I could use c-ares for my needs, since I
> need DNS server support as well as client support, and I'm under the
> impression that c-ares only provides the latter. But the more
> libraries that support libevent, the better.)
>
> yrs,
>
>
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