cleaning-interval question

[Barry Margolin]

In article <cjthjq$11lh$1 at sf1.isc.org>,
 "Walkenhorst, Benjamin" <Benjamin.Walkenhorst at telekom.de> wrote:

> Hello everyone,
> 
> In what respect is BIND's behaviour affected by the value of 
> 'cleaning-interval'?
> BIND will look through its cache every <cleaning-interval> minutes (default: 
> 60) for expired entries and, if it finds any, removes them, that much I could 
> find out in the manual.
> 
> But what happens when an already expired entry is requested again, before 
> being removed from cache? Will the server remove it just then (and probably 
> re-query the RR)? This seems like the only sane behaviour I could come up 
> with for this situation, so ... could someone confirm to me BIND does behave 
> like this? (The alternative looks like passing expired RRs to resolvers which 
> just seems silly).

Yes, that's what it does.  In fact, in early versions of BIND this was 
the *only* way that expired entries would be cleaned up.

> In what respect will modifying this value change the behaviour of the system? 
> Will it just make BIND free up (de facto unused) memory faster (or slower, 
> depending on how I change the value) or are there other effects to be 
> expected?

That's all it does.

> If I am not entirely mistaken, the machines BIND runs on have... sufficient 
> memory at least, so just _saving_ some won't be a big deal. On the other 
> hand, we have to use BIND 9.1.1 right now which apparently doesn't implement 
> a 'max-cache-size' option. So with that unavailable, could I use the 
> 'cleaning-interval' for controlling - or at least influencing - the memory 
> usage of BIND?
> Would setting this value too low (say, 1) adversely influence BIND's 
> performance? (Like if it has a big cache, it might have to go all over it 
> again and again...)

Yes.  You'll be wasting lots of time, since the cache won't have grown 
very much, and few entries will have expired since the last cleanup.

-- 
Barry Margolin, barmar at alum.mit.edu
Arlington, MA
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