[Libevent-users] [PATCH] Add autoconf/make functionality for --disable-dns, --disable-http, and --disable-bevents

[Nick Mathewson]

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.

  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().

Of course, stuff may have changed since then; these problems may be
solved.

(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,
-- 
Nick Mathewson
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