Hello. I searched the archives but it doesn't look like anyone reported this yet. While trying to view the changelog for the latest Debian stretch kernel (http://ftp-master.metadata.debian.org/changelogs//main/l/linux/linux_4.9.82-1+deb9u3_changelog) I received this error from Varnish:
<snip> Error 503 All backends failed or unhealthy All backends failed or unhealthy Guru Mediation: Details: cache-mdw17332-MDW 1520426908 2317177243 Varnish cache server <snip> Derrick
