Intermittent http first read error: EOF

[L Cruzero]

Hi, I'm occasionally seeing this error " http first read error: EOF" in
varnishlog for content that exist, and not exceeding "first_byte_timeout"
TTL
I was considering issuing a restart < 4 on 503's with a URL condition match
since this is happening pretty rarely, I'm seeing the error just 2-3 times
while also getting a 200 for the same html asset 3,000+ times within a
couple of mins of logging.


varnish-4.0.3


# varnishadm "param.show first_byte_timeout"

first_byte_timeout

        Value is: 60.000 [seconds] (default)

        Default is: 60.000

        Minimum is: 0.000

# varnishadm "param.show thread_pool_timeout"

thread_pool_timeout

        Value is: 120.000 [seconds]

        Default is: 300.000

        Minimum is: 10.000


VCL code used to define and use backend where 503 errors are being
generated..

backend wwwdot {

        .host = "web-prod-ssf.domain.ly";

        .port = "80";

        }


if (req.http.host ~ "^(origin-www|www)") {

        set req.backend_hint = wwwdot;

        return(pass);

}

<< BeReq    >> 575646365

-   Begin          bereq 575646364 pass

-   Timestamp      Start: 1453229310.040839 0.000000 0.000000

-   BereqMethod    GET

-   BereqURL       /toprail-domain.html

-   BereqProtocol  HTTP/1.1

-   BereqHeader    DNT: 1

-   BereqHeader    Cookie: bknx_fa=1453197478872; bknx_ss=1453229297581;
CPN_crispkey=;
CPN_geo=eyJpcF9hZGRyZXNzIjoiNzAuMTk2LjEzMi4yMyIsImlwX3R5cGUiOiJNYXBwZWQiLCJOZXR3b3JrIjp7ImNvbm5lY3Rpb25fdHlwZSI6Im1vYmlsZSB3aXJlbGVzcyIsImxpbmVfc3BlZWQiOiJsb3ciLCJpcF9yb3V0aW5nX3R5cGUiO

-   BereqHeader    Accept: */*

-   BereqHeader    User-Agent: Mozilla/5.0 (iPhone; CPU iPhone OS 9_2 like
Mac OS X) AppleWebKit/601.1.46 (KHTML, like Gecko) Version/9.0 Mobile/13C75
Safari/601.1

-   BereqHeader    Accept-Language: en-us

-   BereqHeader    Referer:
http://www.domain.com/outdoors/index.ssf/2014/02/wild_boar_attacks_slidell_man.html

-   BereqHeader    X-Client-Dest-Addr: 69.164.6.110

-   BereqHeader    True-Client-IP: 70.196.132.44

-   BereqHeader    X-Via: 1.1 sw.cds943.dal.llnw.net:8000 (EdgePrism/4.3.1.0),
1.1 cds1158.dal.llnw.net:80 (EdgePrism/4.3.1.0), 1.1 cds1079.lga.llnw.net:80
(EdgePrism/4.3.1.0)

-   BereqHeader    Host: www.domain.com

-   BereqHeader    Accept-Encoding: identity

-   BereqHeader    X-Forwarded-For: 70.196.132.44, 69.164.7.89,
69.164.43.169, 69.164.48.181, 10.51.13.254

-   BereqHeader    X-Varnish: 575646365

-   VCL_call       BACKEND_FETCH

-   VCL_return     fetch

-   BackendOpen    86 wwwdot(69.4.99.100,,80) 10.51.13.97 56085

-   Backend        86 wwwdot wwwdot(69.2.99.10,,80)

-   Timestamp      Bereq: 1453229310.041475 0.000635 0.000635

-   FetchError     http first read error: EOF

-   BackendClose   86 wwwdot(69.4.99.100,,80)

-   Timestamp      Beresp: 1453229310.041717 0.000877 0.000242

-   Timestamp      Error: 1453229310.041720 0.000881 0.000003

-   BerespProtocol HTTP/1.1

-   BerespStatus   503

-   BerespReason   Service Unavailable

-   BerespReason   Backend fetch failed

-   BerespHeader   Date: Tue, 19 Jan 2016 18:48:30 GMT

-   BerespHeader   Server: Varnish

-   VCL_call       BACKEND_ERROR

-   BerespHeader   Content-Type: text/html; charset=utf-8

-   BerespHeader   Retry-After: 5

-   VCL_return     deliver

-   Storage        malloc Transient

-   ObjProtocol    HTTP/1.1

-   ObjStatus      503

-   ObjReason      Backend fetch failed

-   ObjHeader      Date: Tue, 19 Jan 2016 18:48:30 GMT

-   ObjHeader      Server: Varnish

-   ObjHeader      Content-Type: text/html; charset=utf-8

-   ObjHeader      Retry-After: 5

-   Length         286

-   BereqAcct      5960 0 5960 0 0 0

-   End


any suggestions and or ideas on solving this issue would be much
appreciated.

Thanks

-LC
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