In a real deployment scenario, playback should be as robust as possible in the face of server-side problems. As our architecture stands today, playback can suffer from two problems regardless of the amount of backend redundancy that is deployed. Those problems are liveness, where a packager advertises a stale view of live, and dropout, where a packager has gaps in its fragment list.
HDS/HLS fail-over is the server side solution to solve the live-ness and dropout problems in HDS/HLS respectively.
This article describes a basic failover setup with redundant packagers and Varnish as a reverse proxy. The article further provides users a step-by-step guide to writing a basic varnish configuration script to configure Varnish for the failover solution.