RE: hub compliance - dropping ports

[Kevin Hawkins]

Hi again Kieran,

Just re-read your message and you state your application is a HUB in
Perl !! Should have read it more carefully.

I have to say that a hub is such a vital component to the operation
of all the other xAPp's that I feel it should be able to send a dependable
and consistent heartbeat itself.

Plus given the 2 heartbeat timeouts for each of possibly many
connected devices, will those not be handled by forks - or by just by a big
loop, decrementing a timeout counter for each ?

Of course as you're writing a hub you are never going to fall foul
of a timeout yourself at all - and other hubs make no use of your hub
heartbeat - only when you get to writing a xAP that utilises a hub might
you
suffer being timed out. But a network monitor (if there was one) might
flag a failure of your hub which is a significant network failing that has
a
knock on effect to all connected xAP's.

Unless I'm on the wrong track - again :-)

K


> -----Original Message-----
> From: Broadfoot, Kieran J [mailto:<a
href="/group/xAP_developer/post?postID=wvreo8bpG983D_ahKNV8G437IYXp5yPb9WlZryuT3gzkuyKP417ylkXzZ8OY2-24qXLXKMgP7b5uzdIhBarUxQ">kieran.broadfoot@g...</a>]
> Sent: 27 August 2003 08:01
> To: <a
href="/group/xAP_developer/post?postID=EALmTNn59f-ZPgpYGvIichZn5Sy8PcM1kGwA5zNiKz1TL34wo2nYuOm87VL253aHOqY-O4YaUEJU5LtbhChBo1wXTyhj">'xAP_developer@xxxxxxx</a>'
> Subject: [xAP_developer] hub compliance - dropping ports
>
>
> Guys,
>
> A quick question regarding the hub protocol in the spec. It states:
>
> "If no heartbeat is received from a given xAPp for two heartbeat
> intervals,
> then the hub-port is removed from the list."
>
> Ive been writing a hub in perl (well you get hub functionality for
free
> when
> you use the perl xAP module) but as Im lazy and Id like to avoid
> forking (or
> ropey old perl threads) my heartbeats are sent as and when the module
> can.
> This means the hub can never guarantee that two messages should have
> arrived
> in a particular timeframe and conclude that its safe to drop a port.
>
> I guess my question is simple, is it essential for a hub to drop ports
> after
> a given period of time when the cost of continuing to publish to a
> specific
> port is inconsequential in real terms.
>
> Please be nice and help me avoid forking ;-)
>
> thanks
> kieran
>
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