Patchs proposal

[Andreas Ericsson]

nap wrote:
> On Sat, May 16, 2009 at 11:50 AM, Andreas Ericsson <ae at op5.se> wrote:
>> nap wrote:
>>> This is for the circular host check. I use bit 1->5 of
>>> host->is_being_freshened. I'm doing now the hostgroup's service patch.
>>>
>> Thanks a lot! I've mangled the implementation a bit, using macros for
>> the most part and accessing host->circular_path_checked instead of
>> the higher order bits of is_being_freshened. Since it's now using
>> macros, we could re-use this for host- and service dependencies too,
>> as those also have the circular_path_checked variable.
> Yes, the same algorithm can be use. :)
> 
>> Timing values from a config with 151109 hosts:
>> Patched
>> 6.28user 0.19system 0:06.58elapsed 98%CPU (0avgtext+0avgdata 0maxresident)k
>> 0inputs+0outputs (0major+65723minor)pagefaults 0swaps
>>
>> Unpatched
>> Ctrl-C before it was finished, providing these numbers:
>> 3221.77user 0.31system 53:56.51elapsed 99%CPU (0text+0data 0max)k
>> 0inputs+0outputs (0major+67480minor)pagefaults 0swaps
>>
>> So far, your patch provides a speedup of *at least* 51302%. Very nice
>> indeed.
> Thanks,
> 
>> With a more modest configuration (15000 hosts), Nagios patched with your
>> DFS code completes in 0.72 seconds, while vanilla Nagios needs 3m 33s to
>> verify it. In short; Your patch cuts configuration verification down to
>> 0.3% of what it originally required. I suspect we can get rid of the
>> pre-cache thing entirely now. The speedups it provides are really no
>> longer enough to warrant the complexities it entails.
>>
>> I've also verified with some very strange configurations that it doesn't
>> ever miss a circular path chain, and it also prints all elements of a
>> circular path even if that chain in itself contains a circular chain.
>>
>> Consider this:
>> host1 parents: host2
>> host2 parents: host1,host3
>> host3 parents: host1
>>
>> With your patch, all three hosts are printed (as they should). With
>> vanilla Nagios, only host1 and host2 are printed. I simplified this
>> example a bit, since I just added random circular paths to a customer's
>> config when I was testing it out, but it seems your patch is more
>> correct while at the same time scaling linearly with the number of
>> hosts. Thanks indeed.
>>
> Maybe we can take part of my very first email for this patch for the
> documentation. I wrote how the patch is working (with the differents
> state, etc).
> 

There's no need to document this patch really, apart from its effects
which will have to go in a release-note.

> Is the patch ok for the next Nagios version?
> 

Both yes and no. I modified it quite extensively, but I've committed
it to Nagios CVS. The effects of it will be in the next nagios release,
but the exact code you wrote is not there. Check out latest CVS and
have a look in base/config.c and you'll see how it turned out.

-- 
Andreas Ericsson                   andreas.ericsson at op5.se
OP5 AB                             www.op5.se
Tel: +46 8-230225                  Fax: +46 8-230231

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