<div dir="ltr"><p style="margin:0px 0px 1em;padding:0px;border:0px;font-size:15px;clear:both;color:rgb(36,39,41);font-family:arial,"helvetica neue",helvetica,sans-serif">I see sporadic fetch errors (<span style="font-family:consolas,menlo,monaco,"lucida console","liberation mono","dejavu sans mono","bitstream vera sans mono","courier new",monospace,sans-serif;white-space:inherit;background-color:rgb(239,240,241);font-size:13px">http first read error: EOF)</span> from backend but backend is normally healthy. It seems that timeout is not the root issue in this case. What could be the reason?</p><pre style="white-space:pre-wrap;margin-top:0px;margin-bottom:1em;padding:5px;border:0px;font-size:13px;width:auto;max-height:600px;overflow:auto;font-family:consolas,menlo,monaco,"lucida console","liberation mono","dejavu sans mono","bitstream vera sans mono","courier new",monospace,sans-serif;background-color:rgb(239,240,241);word-wrap:normal;color:rgb(36,39,41)"><code style="margin:0px;padding:0px;border:0px;font-family:consolas,menlo,monaco,"lucida console","liberation mono","dejavu sans mono","bitstream vera sans mono","courier new",monospace,sans-serif;white-space:inherit">*   << BeReq    >> 98808229  
-   Begin          bereq 98808228 fetch
-   Timestamp      Start: 1490683823.763272 0.000000 0.000000
-   BereqMethod    GET
-   BereqURL       XXXX
-   BereqProtocol  HTTP/1.1
-   BereqHeader    Pragma: no-cache
-   BereqHeader    Accept: */*
-   BereqHeader    From: bingbot(at)<a href="http://microsoft.com/" target="_blank">microsoft.com</a>
-   BereqHeader    Host: XXXX
-   BereqHeader    User-Agent: Mozilla/5.0 (compatible; bingbot/2.0; +<a href="http://www.bing.com/bingbot.htm" target="_blank">http://www.bing.com/bingbot.<wbr>htm</a>)
-   BereqHeader    Accept-Encoding: gzip
-   BereqHeader    X-Varnish: 98808229
-   VCL_call       BACKEND_FETCH
-   VCL_return     fetch
-   BackendOpen    38 reload_2017-03-20T11:32:44.st2 10.35.78.11 80 172.17.0.2 48388
-   BackendStart   10.35.78.11 80
-   Timestamp      Bereq: 1490683823.763758 0.000487 0.000487
-   <b>FetchError</b>     <b>http first read error: EOF</b>
-   BackendClose   38 reload_2017-03-20T11:32:44.st2
-   Timestamp      Beresp: 1490683823.764271 0.000999 0.000513
-   Timestamp      Error: 1490683823.764277 0.001005 0.000005
-   BerespProtocol HTTP/1.1
-   BerespStatus   503
-   BerespReason   Service Unavailable
-   BerespReason   Backend fetch failed
-   BerespHeader   Date: Tue, 28 Mar 2017 06:50:23 GMT
-   BerespHeader   Server: Varnish
-   VCL_call       BACKEND_ERROR
-   BereqHeader    X-Varnish-Backend-5xx: 1
-   VCL_return     retry
-   Timestamp      Retry: 1490683823.764294 0.001022 0.000017
-   Link           bereq 97940444 retry
-   End  </code></pre></div>