Mailing List Archive: Varnishncsa Random Log Sampling ?

Varnishncsa Random Log Sampling ?

Mar 2, 2020, 3:13 AM

Post #1 of 3 (647 views)

Hello,

I am sending my Varnish log to to remote SAAS solution I and want to
improve logs costs by implementing a server side sampling solution .

First I splitted Varnishnncsa into two service one for error logs and the
other for acces logs :

CGroup: /system.slice/varnishncsa-error.service
??18458 /usr/bin/varnishncsa -c -b -a -w
/var/log/varnish/varnishncsa-error.log -D -P
/run/varnishncsa/varnishncsa-error.pid -f
/etc/varnish/varnishncsa_logmatic.format -q *Status > 399

CGroup: /system.slice/varnishncsa.service
??18347 /usr/bin/varnishncsa -c -b -a -w
/var/log/varnish/varnishncsa-access.log -D -P
/run/varnishncsa/varnishncsa-access.pid -f
/etc/varnish/varnishncsa_logmatic.format -q *Status < 400

Is there Any way to go further with varnishncsa and perform and random
sampling of my access logs ? for example write only 10 % of access logs

If it's not possible with varnishncsa any Suggestion ? I tried rsyslog
random sampling but I am facing memory leaks while stress testing server
with high load

Thanks,

Yassine

Re: Varnishncsa Random Log Sampling ? [ In reply to ]

dridi at varni

Mar 2, 2020, 3:43 AM

Post #2 of 3 (647 views)

Permalink

On Mon, Mar 2, 2020 at 11:15 AM Yassine Aouadi
<yassine.aouadi90@gmail.com> wrote:
>
>
> Hello,
>
> I am sending my Varnish log to to remote SAAS solution I and want to improve logs costs by implementing a server side sampling solution .
>
> First I splitted Varnishnncsa into two service one for error logs and the other for acces logs :
>
> CGroup: /system.slice/varnishncsa-error.service
> ??18458 /usr/bin/varnishncsa -c -b -a -w /var/log/varnish/varnishncsa-error.log -D -P /run/varnishncsa/varnishncsa-error.pid -f /etc/varnish/varnishncsa_logmatic.format -q *Status > 399
>
> CGroup: /system.slice/varnishncsa.service
> ??18347 /usr/bin/varnishncsa -c -b -a -w /var/log/varnish/varnishncsa-access.log -D -P /run/varnishncsa/varnishncsa-access.pid -f /etc/varnish/varnishncsa_logmatic.format -q *Status < 400
>
>
> Is there Any way to go further with varnishncsa and perform and random sampling of my access logs ? for example write only 10 % of access logs
>
> If it's not possible with varnishncsa any Suggestion ? I tried rsyslog random sampling but I am facing memory leaks while stress testing server with high load

Hi,

I think the closest to what you want is rate limiting, see the
documentation for the varnishstat -R option. Otherwise you can always
do the sampling one step downstream and instead of sending
varnishncsa-<something>.log whenever logrotate triggers a rotation you
run script that sends 1 line every 10 lines. But I think rate limiting
with -R is simpler and instead of a percentage that depends highly on
your traffic you can actually get a limit according to a budget since
you wish to reduce costs.

Dridi
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Re: Varnishncsa Random Log Sampling ? [ In reply to ]

geoff at uplex

Mar 2, 2020, 4:18 AM

Post #3 of 3 (646 views)

Permalink

On 3/2/20 12:13, Yassine Aouadi wrote:
>
> Is there Any way to go further with varnishncsa and perform and random
> sampling of my access logs ? for example write only 10 % of access logs

I've done that with log queries in the varnishncsa or varnishlog command
line. For example, this query filters out all logs for which the
X-Varnish header does not end in 0:

-q 'RespHeader:X-Varnish !~ "0$"'

https://varnish-cache.org/docs/trunk/reference/vsl-query.html

The queries can use regular expressions, as this one does, so you can do
things like filter for the range [0-4], [02468] for the even numbers, or
whatever your imagination comes up with.

If you know that your site always produces a certain kind of content,
say a cookie whose value is hex digits, you can base your filter on
that, say something like [89a-f].

If you use that X-Varnish example, bear in mind that it only applies to
client logs. X-Varnish appears in backend request headers, so it would
have to be BereqHeader:X-Varnish.

HTH,
Geoff
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