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From Costin Manolache <cos...@gmail.com>
Subject Re: APR/native and per socket timeouts.
Date Mon, 21 May 2012 17:30:54 GMT
On Mon, May 21, 2012 at 9:29 AM, Mark Thomas <markt@apache.org> wrote:

> On 21/05/2012 15:26, Costin Manolache wrote:
> > My understanding is that the timeout is implemented in poll.c maintain()
> -
> > by scanning the socket list in C.
> >
> > Why not doing the same thing in java - i.e. don't touch native code, have
> > all sockets 'long', and close whenever you need from java ?
>
> The timeout is also used in poll so it wouldn't be a completely clean
> solution.


How is it used in poll ? The poll can be arbitrary - there is no need to
guarantee that sockets timeout at the exact moment, it can happen later.
If poll time is 1/2 hour - than if no event happens you'll check every 1/2
hour which sockets are expired.

The benefit of doing it in java is that you have more control - and may use
more advanced structures ( C is just a loop over the list of sockets,
wouldn't scale very well to 100K+ sockets - which are probably normal case
for websocket ).



Costin



> It would probably work but there might be some odd edge cases.
> It think it is probably better - for now - to keep this in native.
>




>
> Mark
>
>
> >
> > Costin
> >
> > On Mon, May 21, 2012 at 5:55 AM, Mark Thomas <markt@apache.org> wrote:
> >
> >> On 20/05/2012 21:47, Mladen Turk wrote:
> >>> On 05/20/2012 08:37 PM, Mark Thomas wrote:
> >>>> Therefore, I intend modifying the APR/native code to support per
> socket
> >>>> time outs. I would be grateful if those of you with more C knowledge
> >>>> than I (which is most people on this list) could:
> >>>> a) tell me now if this is a crazy idea (and why)
> >>>> b) keep an extra close eye on any commit of mine that touches the C
> >> code.
> >>>>
> >>>
> >>> This should be easy to implement.
> >>> Inside native we track socket_ttl for each socket.
> >>> Currently when  socket is added it's set to apr_time_now()
> >>> and later compared with max_ttl (usually keepAliveTimeout).
> >>>
> >>> We can add new API that would add socket with timeout relative
> >>> to max_ttl. A bit awkward but wouldn't create backward incompatibility.
> >>>
> >>> Take a look at poll.c add function.
> >>> The new addt would have additional timeout parameter and
> >>> you would set:
> >>> ...
> >>> if (p->max_ttl > 0)
> >>>         p->socket_ttl[p->nelts] = apr_time_now() + J2T(timeout);
> >>> ...
> >>>
> >>> Now that new timeout param would actually be called as
> >>> Poll.add(pollset, socket, events, perSocketPollTimeout -
> >> keepAliveTimeout);
> >>> given that keepAliveTimeout was used for Poll.setTtl(keepAliveTimeout);
> >>>
> >>> So effectively socket_ttl would become 'now() - ttlOffset'
> >>
> >> Thanks for confirming I am heading in the right direction with this. I'm
> >> hesitant to follow exactly the path above. While it is a minimal change
> >> from the current code, I think it could be difficult for folks new to
> >> the code to figure out what is going on.
> >>
> >> I'd like to see if I can come up with a change that will be more obvious
> >> on first reading. I expect it will be a little more invasive than the
> >> change you suggested. Depending on my level of confidence, I'll either
> >> post a patch or commit the change when I have something concrete.
> >>
> >> Cheers,
> >>
> >> Mark
> >>
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> >>
> >>
> >
>
>
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>

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