Good day everyone,
I am trying to get to the bottom of the 503s sporadically logged by our Varnish
servers. During monitoring, it all comes down to monitoring the state of my
backends ++ varnishlog.
Most of the 503s come with a FetchError “backend write error: 0 (Success)” —
and I can’t seem to find anything on the internet to describe what this might
mean.
—> FetchError c backend write error: 0 (Success) <—
Also, none of the relevant counters in varnishstat are showing any increase
(i.e. backend_unhealthy, backend_busy, backend_fail, fetch_failed..)
For that same request, looking at ReqEnd, it doesn’t look to me like any
timeout was reached (like connect_timeout, first_byte_timeout,
between_bytes_timeout, ..)
—> ReqEnd c 221990096 1444847550.110866785 1444847550.116131306
0.000048876 0.000905752 0.004358768 <—
Any chance we could get a list of possible FetchError messages and what they
might mean — at least something to put us on a right track? Would surely help
knowing where to start looking, especially when everything seems fine.
Also, in this FetcError scenario, is it expected to see retries from Varnish?
If so, why would Varnish only retry some of the backends in a director and not
all of them (or the .retries value)?
44 VCL_return c hash
44 VCL_call c pass pass
44 Backend c 20 drpau_ssl_director drpau34ssl
44 FetchError c backend write error: 0 (Success)
44 Backend c 51 drpau_ssl_director drpau31ssl
44 FetchError c backend write error: 0 (Success)
44 VCL_call c error deliver
44 VCL_call c deliver deliver
44 TxProtocol c HTTP/1.1
44 TxStatus c 503
44 TxResponse c Service Unavailable
Should these be reflected in varnishstat’s “backend_retry”?
Thank you guys!
Vlad Rusu
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