Best practice for caching scenario with different backend servers but same content

[Hamidreza Hosseini]

Hi,
I want to use varnish in my scenario as cache service, I have about 10 http servers that serve Hls fragments as the backend servers and about 5 varnish servers for caching purpose, the problem comes in when I use round-robin director for backend servers in varnish,
if a varnish for specific file requests to one backend server and for the same file but to another backend server it would cache that file again because of different Host headers ! so my solution is using fallback director instead of round-robin as follow:

```
In varnish-1:
    new hls_cluster = directors.fallback();
    hls_cluster.add_backend(b1());
    hls_cluster.add_backend(b2());
    hls_cluster.add_backend(b3());
    hls_cluster.add_backend(b4());
    hls_cluster.add_backend(b5());
    hls_cluster.add_backend(b6());
    hls_cluster.add_backend(b7());
    hls_cluster.add_backend(b8());
    hls_cluster.add_backend(b9());
    hls_cluster.add_backend(b10());



In varnish-2:
    new hls_cluster = directors.fallback();
    hls_cluster.add_backend(b10());
    hls_cluster.add_backend(b1());
    hls_cluster.add_backend(b2());
    hls_cluster.add_backend(b3());
    hls_cluster.add_backend(b4());
    hls_cluster.add_backend(b5());
    hls_cluster.add_backend(b6());
    hls_cluster.add_backend(b7());
    hls_cluster.add_backend(b8());
    hls_cluster.add_backend(b9());


In varnish-3:
    new hls_cluster = directors.fallback();
    hls_cluster.add_backend(b9());
    hls_cluster.add_backend(b1());
    hls_cluster.add_backend(b2());
    hls_cluster.add_backend(b3());
    hls_cluster.add_backend(b4());
    hls_cluster.add_backend(b5());
    hls_cluster.add_backend(b6());
    hls_cluster.add_backend(b7());
    hls_cluster.add_backend(b8());
    hls_cluster.add_backend(b10());

```
But I think this is not the best solution, because there is no load balancing despite, I used different backend for the first argument of fallback directive,
What is varnish recommendation for this scenario?



-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://www.varnish-cache.org/lists/pipermail/varnish-misc/attachments/20210801/f4199264/attachment-0001.html>