Hi,
Thanks to you and all varnish team for such answers that helped me alot,
I read the default varnish cache configuration again:
https://github.com/varnishcache/varnish-cache/blob/6.0/bin/varnishd/builtin.vcl
and find out vcl_hash as follow:
```
sub vcl_hash {
hash_data(req.url);
if (req.http.host) {
hash_data(req.http.host);
} else {
hash_data(server.ip);
}
return (lookup);
}
```
So, if I change vcl_hash like following , would it be enough for my purpose?(I
mean caching the same object from different backends just once with roundrobin
directive !:)
```
sub vcl_hash {
hash_data(req.url);
return (lookup);
}
```
By this config I told varnish just cache the content based on the 'req.url' not
'req.http.host' therefore with the same content but different backend varnish
would cache once(If I want to use round robin directive instead of shard
directive ), Is this true? what bad consequences may it cause in the future by
this configuration?
________________________________
From: varnish-misc
<[email protected]> on behalf of
Hamidreza Hosseini <[email protected]>
Sent: Sunday, August 1, 2021 4:17 AM
To: [email protected] <[email protected]>
Subject: Best practice for caching scenario with different backend servers but
same content
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?
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