Log slow backend requests. VSL-query?

[Danila Vershinin]

Thank you very much, Geoff.

> On 21 Mar 2017, at 21:28, Geoff Simmons <geoff at uplex.de> wrote:
> 
> On 03/21/2017 07:11 PM, Danila Vershinin wrote:
>> 
>> Trying to log only the slow backend requests:
>> 
>> varnishncsa -b -q 'Timestamp:Process[2] > 0.1’
> 
> Timestamp:Process only appears in the client-side logs, but with -b
> you're filtering for the backend logs.
> 
> The "Backend fetch timestamps" section at the bottom of vsl(7) tells
> you the names of the timestamps for backends:
> 
> http://www.varnish-cache.org/docs/5.1/reference/vsl.html#backend-fetch-timestamps
> 
> The one you're probably looking for is Timestamp:Beresp[3]. Beresp is
> the timestamp set after receiving backend response headers (the first
> timestamp recorded after the backend starts sending a response). Field
> 3 is the time elapsed since the most recent timestamp, which would be
> Bereq (backend request sent), so this is the best measurement of how
> fast or slow a backend responds after receiving a request.
> 
> One thing to watch out for: if there is a fetch error such as a
> timeout that results in no backend response being received at all,
> then Timestamp:Beresp isn't recorded in the log. Instead of that you
> get Timestamp:Error, so you might want to query for Timestamp:Error[3]
> as well.
> 
> 
> HTH,
> Geoff
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