[Gross] false positives

Jesse Thompson jesse.thompson at doit.wisc.edu
Wed Dec 17 19:10:33 EET 2008


Imri Zvik wrote:
> On Wednesday 17 December 2008 14:22:51 Eino Tuominen wrote:
>> Jesse Thompson wrote:
>>> You probably need to raise filter_bits setting; especially since you are
>>> using such a large rotate_interval.
>>>
>>> Or, if you use the block_threshold functionality, most messages will be
>>> blocked and not added to the filters, which reduces the chance of false
>>> positives.
>> Indeed, that's seems to be the best way.
>>
>> Just for the record, we are now talking false matches, or collisions in
>> the bloom filter, not false positives.
> 
> I forgot to CC the list on my reply to Jesse:
> 
> If I raise the filter bit, grossd crashes with segmentation fault.
> 
> Linux greylist2 2.6.9-55.ELsmp #1 SMP Fri Apr 20 16:36:54 EDT 2007 x86_64 
> x86_64 x86_64 GNU/Linux

During the initial filter replication?  We saw a similar problem, but it 
was triggered by Solaris 10 patching.  We were never able to figure out 
the root cause.  Lowering the filter_bits allowed the filters to sync 
before it crashed.

Since you can't raise the filter_bits, can you lower the 
rotate_interval?  That should lower the chance of false matches.

Jesse
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