<html><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class="">Good day everyone, <div class=""><br class=""></div><div class="">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.</div><div class=""><br class=""></div><div class="">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.</div><div class=""><br class=""></div><div class="">—> FetchError c backend write error: 0 (Success) <—</div><div class=""><br class=""></div><div class="">Also, none of the relevant counters in varnishstat are showing any increase (i.e. backend_unhealthy, backend_busy, backend_fail, fetch_failed..)</div><div class=""><br class=""></div><div class="">For that same request, looking at ReqEnd, it doesn’t look to me like any timeout was reached (like connect_timeout, <span style="line-height: 16.8px; white-space: pre; widows: 1; background-color: rgb(255, 255, 255);" class="">first_byte_timeout</span>, <span style="line-height: 16.8px; white-space: pre; widows: 1; background-color: rgb(255, 255, 255);" class="">between_bytes_timeout, ..</span>)</div><div class=""><br class=""></div><div class="">—> ReqEnd c 221990096 1444847550.110866785 1444847550.116131306 0.000048876 0.000905752 0.004358768 <—</div><div class=""><br class=""></div><div class=""><br class=""></div><div class=""><b class="">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.</b></div><div class=""><br class=""></div><div class="">Also, in this FetcError scenario, <b class="">is it expected to see retries from Varnish?</b> If so, why would Varnish only retry some of the backends in a director and not all of them (or the .retries value)?</div><div class=""><br class=""></div><div class=""><div class=""> 44 VCL_return c hash</div><div class=""> 44 VCL_call c pass pass</div><div class=""> 44 Backend c 20 drpau_ssl_director drpau34ssl</div><div class=""> 44 FetchError c backend write error: 0 (Success)</div><div class=""> 44 Backend c 51 drpau_ssl_director drpau31ssl</div><div class=""> 44 FetchError c backend write error: 0 (Success)</div><div class=""> 44 VCL_call c error deliver</div><div class=""> 44 VCL_call c deliver deliver</div><div class=""> 44 TxProtocol c HTTP/1.1</div><div class=""> 44 TxStatus c 503</div><div class=""> 44 TxResponse c Service Unavailable</div></div><div class=""><br class=""></div><div class="">Should these be reflected in varnishstat’s “backend_retry”?</div><div class=""><br class=""></div><div class="">Thank you guys!</div><div class="">Vlad Rusu</div></body></html>