[16863] in Kerberos_V5_Development
Re: Asynchronous operation and krb5 dependencies
daemon@ATHENA.MIT.EDU (Simo Sorce)
Tue Jun 7 16:20:51 2011
From: Simo Sorce <simo@redhat.com>
To: Sam Hartman <hartmans@mit.edu>
In-Reply-To: <tslaadt5xbe.fsf@mit.edu>
Date: Tue, 07 Jun 2011 16:20:43 -0400
Message-ID: <1307478043.2613.191.camel@willson.li.ssimo.org>
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Cc: Nico Williams <nico@cryptonector.com>, "krbdev@mit.edu" <krbdev@mit.edu>
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On Tue, 2011-06-07 at 14:08 -0400, Sam Hartman wrote:
> >>>>> "Greg" == Greg Hudson <ghudson@MIT.EDU> writes:
>
> Greg> On Mon, 2011-06-06 at 06:46 -0400, Nico Williams wrote:
> >> (Well, but then, how do you deal with APIs like the GSS-API where
> >> there's no obvious way to reference any particular context due to
> >> the lack of a krb5_context-like argument?)
>
> Greg> For the purposes of libkrb5, we're taking the view that an
> Greg> application will only need one main loop implementation. (It
> Greg> may need multiple instances of the main loop, but we're not
> Greg> trying to support an application which uses libevent in one
> Greg> thread and g_main_* in another.) So, when the application
> Greg> provides its vtable to libverto, that will get stored in
> Greg> global process state and used for all async operations--no
> Greg> need for a context.
>
> I'm kind of uncomfortable with the idea that an application will only
> need one main loop implementation.
> krb5 tends to get called from things like nss plugins, sasl interfaces
> to other applications, etc.
>
> If the main application is asynchronous then it mostly will have one
> event loop.
> The only exception is if you can get some sub-component with its own
> event loop to tell you what file descriptors and timeouts it cares
> about, then you can backend one event loop into another.
>
> However if there are parts or threads of the application that are
> synchronous, those parts can easily have their own event loops for
> semi-asynchronous operation. For example, krb5 could do such a thing to
> speed up the interactions between DNS resolution and KDC contacting
> within the synchronous APIs.
>
> For this reason, I do not think the one-event-loop-per-application
> assumption is sound.
Absolutely right.
Simo.
--
Simo Sorce * Red Hat, Inc * New York
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