Varnish:
Configuring Varnish Server i.e. a Cache Server
https://varnish-cache.org/docs/5.1/reference/varnishd.html#http-resp-hdr-len
/opt/bitnami/varnish/varnishd
varnishd [-a address[:port][,PROTO]] [-b host[:port]] [-C] [-d] [-F] [-f config] [-h type[,options]] [-I clifile] [-i identity] [-j jail[,jailoptions]] [-l vsl[,vsm]] [-M address:port] [-n name] [-P file] [-p param=value] [-r param[,param...]] [-S secret-file] [-s [name=]kind[,options]] [-T address[:port]] [-t TTL] [-V] [-W waiter] [-x parameter|vsl|cli|builtin] [-?]
---
How to fix 503: Backend Fetch error
Give it a try; no guarantee. Purge Varnish cache as well. magento cache clearing also causes varnish cache Purge
https://community.magento.com/t5/Magento-2-x-Programming/how-to-fix-Error-503-Backend-fetch-failed/td-p/84061
----
Configure And Use Varnish (TM)
See if your version and platform is right before applying
https://docs.bitnami.com/bch/apps/wordpress/administration/configure-use-varnish/
Deploy content
setup:static-content:deploy [-f|--force] [-s|--strategy [STRATEGY]] [-a|--area [AREA]] [--exclude-area [EXCLUDE-A
REA]] [-t|--theme [THEME]] [--exclude-theme [EXCLUDE-THEME]] [-l|--language [LANGUAGE]] [--exclude-language [EXCL
UDE-LANGUAGE]] [-j|--jobs [JOBS]] [--max-execution-time [MAX-EXECUTION-TIME]] [--symlink-locale] [--content-versi
on CONTENT-VERSION] [--refresh-content-version-only] [--no-javascript] [--no-css] [--no-less] [--no-images] [--no
-fonts] [--no-html] [--no-misc] [--no-html-minify] [--] [<languages>...]
By
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