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</o:shapelayout></xml><![endif]--></head><body lang=EN-GB link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span style='color:#1F497D'>I found the issue myself, perhaps it will help others.<o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'>The backend servers were using keep-alive with varnish, and whenever varnish got a timeout from the backend, it would retry the request exactly once (hardcoded) because the initial backend was marked as “recycled”. <o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'>Disabling keep-alive on the backend servers resolved my issue.<o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='color:#1F497D'>Good luck,<o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'>Traian<o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p><div><div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0cm 0cm 0cm'><p class=MsoNormal><b><span lang=EN-US style='font-size:10.0pt;font-family:"Tahoma","sans-serif";mso-fareast-language:EN-GB'>From:</span></b><span lang=EN-US style='font-size:10.0pt;font-family:"Tahoma","sans-serif";mso-fareast-language:EN-GB'> varnish-misc-bounces@varnish-cache.org [mailto:varnish-misc-bounces@varnish-cache.org] <b>On Behalf Of </b>Traian Bratucu<br><b>Sent:</b> Tuesday, December 07, 2010 11:37 AM<br><b>To:</b> 'varnish-misc@varnish-cache.org'<br><b>Subject:</b> varnish default retries on backend timeout?<o:p></o:p></span></p></div></div><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><span lang=EN-US>Hello,<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US>We have been using Varnish for a while and encountered a specific problem I don’t seem to be able to figure out. Apparently on a POST request to the backend, for which the backend times out, the request is automatically retried by varnish a second time.<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US>Obviously that is a big problem since POST data gets submitted twice. I do not have any restart statements in the VCL so I guess this is some default Varnish behavior, hopefully controlled by some global parameter.<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US>Here is what I get logged:<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US>-------------<o:p></o:p></span></p><p class=MsoNormal><span lang=DE style='mso-fareast-language:EN-GB'> 32 Backend c 5 xxx_authenticated black_instance_1<o:p></o:p></span></p><p class=MsoNormal><span lang=DE style='mso-fareast-language:EN-GB'> 32 FetchError c http first read error: -1 11 (Resource temporarily unavailable)<o:p></o:p></span></p><p class=MsoNormal><span lang=DE style='mso-fareast-language:EN-GB'> 32 Backend c 87 xxx_authenticated gray_instance_2<o:p></o:p></span></p><p class=MsoNormal><span lang=DE style='mso-fareast-language:EN-GB'> 32 FetchError c http first read error: -1 11 (Resource temporarily unavailable)<o:p></o:p></span></p><p class=MsoNormal><span lang=DE style='mso-fareast-language:EN-GB'> 32 VCL_call c error deliver<o:p></o:p></span></p><p class=MsoNormal><span lang=DE style='mso-fareast-language:EN-GB'> 32 VCL_call c deliver deliver<o:p></o:p></span></p><p class=MsoNormal><span lang=DE style='mso-fareast-language:EN-GB'> 32 TxProtocol c HTTP/1.1<o:p></o:p></span></p><p class=MsoNormal><span lang=DE style='mso-fareast-language:EN-GB'> 32 TxStatus c 503<o:p></o:p></span></p><p class=MsoNormal><span lang=DE style='mso-fareast-language:EN-GB'>-------------<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US>Is there a way to avoid this double post?<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US>Thank you,<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US>Traian<o:p></o:p></span></p></div></body></html>