[Dnsmasq-discuss] Eviction statistics is always zero

Leonardo da Mata leonardo.mata at samsara.com
Wed Apr 14 09:52:14 UTC 2021


Yes, you are right, but I have also found another explanation for it,
the SMALLDNAME constant that is preventing larger names to be cached. I was
able to compile a version with a bigger value for this constant and could
see the eviction metric changing.

Thanks for the answers :)

On Mon, Apr 12, 2021 at 6:03 PM Simon Kelley <simon at thekelleys.org.uk>
wrote:

> It's not absolute, since they may have been caught at the end of cache
> lifetime upstream, but the Time To Live values of one second and five
> seconds in those records suggests it's going to be pretty hard for them
> to hang around in the dnsmasq cache long enough to be evicted.
>
>
> Simon.
>
>
> On 12/04/2021 15:03, Leonardo da Mata wrote:
> > Hello, thanks for the answer.
> >
> > The queries I sent are for AWS rds resolution names, I repeated the
> > experiments with a sample of simple urls and cache size of 2 and could
> > see the eviction metric.
> >
> > I think there might be something on the AWS rds that might prevent it
> > from being cached (Some data is redacted)
> >
> >   dig prod-authdb.cluster-ro-h2dic5akfled.us-west-2.rds.amazonaws.com
> > <
> https://urldefense.com/v3/__http://prod-authdb.cluster-ro-h2dic5akfled.us-west-2.rds.amazonaws.com__;!!Nn3RWQ1l!fBXF8tRpYFkLuTtl4PrzPu-P9_zJwPTWfjzqm2nNlu71uPwfT7OoctFKbAlQT0DMnP8$
> >
> > @172.0.0.1 <
> https://urldefense.com/v3/__http://172.0.0.1__;!!Nn3RWQ1l!fBXF8tRpYFkLuTtl4PrzPu-P9_zJwPTWfjzqm2nNlu71uPwfT7OoctFKbAlQbdcrODk$
> >
> >
> > ; <<>> DiG 9.11.4-P2-RedHat-9.11.4-26.P2.amzn2.4 <<>>
> > prod-authdb.cluster-ro-h2dic5akfled.us-west-2.rds.amazonaws.com
> > <
> https://urldefense.com/v3/__http://prod-authdb.cluster-ro-h2dic5akfled.us-west-2.rds.amazonaws.com__;!!Nn3RWQ1l!fBXF8tRpYFkLuTtl4PrzPu-P9_zJwPTWfjzqm2nNlu71uPwfT7OoctFKbAlQT0DMnP8$
> >
> > @172.0.0.1 <
> https://urldefense.com/v3/__http://172.0.0.1__;!!Nn3RWQ1l!fBXF8tRpYFkLuTtl4PrzPu-P9_zJwPTWfjzqm2nNlu71uPwfT7OoctFKbAlQbdcrODk$
> >
> > ;; global options: +cmd
> > ;; Got answer:
> > ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 60600
> > ;; flags: qr rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 0, ADDITIONAL: 1
> >
> > ;; OPT PSEUDOSECTION:
> > ; EDNS: version: 0, flags:; udp: 4096
> > ;; QUESTION SECTION:
> > ;prod-authdb.cluster-ro-h2dic5akfled.us-west-2.rds.amazonaws.com
> > <
> https://urldefense.com/v3/__http://prod-authdb.cluster-ro-h2dic5akfled.us-west-2.rds.amazonaws.com__;!!Nn3RWQ1l!fBXF8tRpYFkLuTtl4PrzPu-P9_zJwPTWfjzqm2nNlu71uPwfT7OoctFKbAlQT0DMnP8$
> >. IN
> >    A
> >
> > ;; ANSWER SECTION:
> > prod-authdb.cluster-ro-h2dic5akfled.us-west-2.rds.amazonaws.com
> > <
> https://urldefense.com/v3/__http://prod-authdb.cluster-ro-h2dic5akfled.us-west-2.rds.amazonaws.com__;!!Nn3RWQ1l!fBXF8tRpYFkLuTtl4PrzPu-P9_zJwPTWfjzqm2nNlu71uPwfT7OoctFKbAlQT0DMnP8$
> >. 1
> > IN CNAME     prod-authdb-1.h2dic5akfled.us-west-2.rds.amazonaws.com
> > <
> https://urldefense.com/v3/__http://prod-authdb-1.h2dic5akfled.us-west-2.rds.amazonaws.com__;!!Nn3RWQ1l!fBXF8tRpYFkLuTtl4PrzPu-P9_zJwPTWfjzqm2nNlu71uPwfT7OoctFKbAlQrgNuWU8$
> >.
> > prod-authdb-1.h2dic5akfled.us-west-2.rds.amazonaws.com
> > <
> https://urldefense.com/v3/__http://prod-authdb-1.h2dic5akfled.us-west-2.rds.amazonaws.com__;!!Nn3RWQ1l!fBXF8tRpYFkLuTtl4PrzPu-P9_zJwPTWfjzqm2nNlu71uPwfT7OoctFKbAlQrgNuWU8$
> >. 5 IN A
> > 10.0.4.23
> >
> > ;; Query time: 49 msec
> > ;; SERVER: 172.0.0.1#53(172.0.0.1)
> > ;; WHEN: Mon Apr 12 12:55:08 UTC 2021
> > ;; MSG SIZE  rcvd: 157
> >
> >
> > Is CNAME not cached?
> >
> > On Fri, Apr 9, 2021 at 10:46 PM Geert Stappers <stappers at stappers.nl
> > <mailto:stappers at stappers.nl>> wrote:
> >
> >     On Fri, Apr 09, 2021 at 10:39:41AM +0100, Leonardo da Mata wrote:
> >     > On Thu, Apr 8, 2021 at 10:50 PM Simon Kelley wrote:
> >     > > On 08/04/2021 10:37, Leonardo da Mata wrote:
> >     > > > Hello, recently I've done some experiments with dnsmasq
> >     reaching 4k qps
> >     > > > and, even with a very small cache size of 100 entries, I can't
> >     see the
> >     > > > evictions stats to increase. It always stays at zero.
> >     > > >
> >     > > > I'm wondering if anyone can see this data on their side and if
> >     there
> >     > > > might be any problem with the statistics count or something
> >     that might
> >     > > > interfere with this data.
> >     > > >
> >     > >
> >     > > Thu Apr  8 21:33:08 2021 daemon.info <
> https://urldefense.com/v3/__http://daemon.info__;!!Nn3RWQ1l!fBXF8tRpYFkLuTtl4PrzPu-P9_zJwPTWfjzqm2nNlu71uPwfT7OoctFKbAlQOMriH8A$
> >
> >     dnsmasq[23124]: cache size 600,
> >     > > 58/15779 cache insertions re-used unexpired cache entries.
> >     > >
> >     > >
> >     > > What are you using as your test query set?
> >     > >
> >     > >
> >     >
> >     > I'm using a sample of queries from my services, but I'm
> introducing an
> >     > artificial qps with flame using this sample.
> >     >
> >
> >     FWIW "this sample" did not reach my end of the Internet.
> >
> >
> >     Please recieve
> >     > > What are you using as your test query set?
> >     as
> >     } } Send your test query set, so we can reproduce the observation.
> >
> >
> >
> >     Groeten
> >     Geert Stappers
> >     --
> >     Silence is hard to parse
> >
> >
> >
> > --
> > Leonardo da Mata
> > <
> https://urldefense.com/v3/__http://goog_881972804/__;!!Nn3RWQ1l!fBXF8tRpYFkLuTtl4PrzPu-P9_zJwPTWfjzqm2nNlu71uPwfT7OoctFKbAlQwhtzT8k$
> >
> > leonardo.mata at samsara.com <mailto:leonardo.mata at samsara.com>
> >
> > _______________________________________________
> > Dnsmasq-discuss mailing list
> > Dnsmasq-discuss at lists.thekelleys.org.uk
> >
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> >
>
>
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>


-- 
Leonardo da Mata
<http://goog_881972804/>
leonardo.mata at samsara.com
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