I am Getting a lot of varnish 503 error un uncached pages , all these error have one thing in common , checking varnish logs it stats "FetchError overflow". Also error is not consistent , sometimes its error and other times page open Perfectly. My guess its some kind of memory buffer overflow, can any one ever witnessed same error , or can point me to some Place. Version of Varnish is 5.2
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6Did you try to increase in `/etc/default/varnish` parameter `workspace_backend` i.e. to `131072`? try adding there i.e. following `-p http_resp_hdr_len=65536 -p http_resp_size=98304 -p workspace_backend=131072`. Restart of Varnish-service is needed after those changes. – Elvin Risti Apr 30 '18 at 12:17
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i can confirm @ElvinRisti 's solution, although i had to set even higher buffer sizes. – scones Jun 19 '18 at 15:44
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@scones How do you determine the proper buffer sizes etc to set these to? – DOfficial May 27 '21 at 21:01
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@DOfficial best guess + trial and error. there is no big secret :) – scones May 28 '21 at 07:55
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There are several varnish parameters you can try to add/increase in /etc/default/varnish
to fix these issues. Adjust the sizes and see what works in your situation.
E.g.:
-p http_resp_hdr_len=32M -p http_resp_size=32M -p http_req_hdr_len=32M -p http_req_size=32M -p workspace_backend=32M -p workspace_client=32M
Make sure to reload Varnish after changing configs.

Gerard de Visser
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