Broadening the scope of the negative connection cache

[Sam Liddicott]

I think the timeout should relate to the amount of time that will be wasted to timeout again and the exponential decay of how much time has (recently) been wasted.

Iptables connrate match has a good formula.

Sam



-----Original Message-----
From: Gerald (Jerry) Carter <jerry at samba.org>
Sent: 14 May 2008 18:46
To: Marc VanHeyningen <marc.vanheyningen at isilon.com>
Cc: samba-technical at lists.samba.org
Subject: Re: Broadening the scope of the negative connection cache

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Marc VanHeyningen wrote:
> Gerald (Jerry) Carter sed:
>>> The obvious solution would be to migrate the negative 
>>> connection cache to be stored in a different way, probably
>>> as a TDB file.  This would allow every child process to share
>>> the failure information.
>> I believe the easiest way to achieve this is simply to
>> use the gencache API and set a 60 second TTL on entries.
> 
> Sounds good, but a 60 second TTL seems too short to me.  Attempting 
> to find a host and having it fail to respond can take a significant 
> fraction of 60 seconds in some (admittedly unusual) cases.
> 
> Probably the best system is an adaptive one, which increases the 
> TTL of the negative entry the longer the target remains inaccessible,
> but that's more complexity than this situation really warrants.

Anything to reduce timeouts is fine.  Let's just make one
change at a time.  Moving to gencache here is the first step.



jerry

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