On Sat, Aug 14, 2021 at 10:54 AM Hamidreza Hosseini <[email protected]> wrote: > > 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?
In this case req.http.host usually refers to the the domain end users resolve to find your varnish server (or other hops in front of it). It is usually the same for every client, let's take www.myapp.com as an example. If your varnish server is in front of multiple services, you should be handling the different host headers explicitly. For exampe if you have exactly two domains you should normalize them to some canonical form. Using the same example domain that could be www.myapp.com and static.myapp.com for instance. In that case hashing the URL only would prevent you from adding new domains through your Varnish server. It won't hurt if you know you will only ever have one domain to deal with, but hashing the host will also not hurt as long as you normalize it to a unique value. You are correct that by default hashing the request appropriately will help the shard director do the right thing out of the box. I remember however that you only wanted to hash a subset of the URL for video segments, so hashing the URL as-is won't provide the behavior you are looking for. Dridi _______________________________________________ varnish-misc mailing list [email protected] https://www.varnish-cache.org/lists/mailman/listinfo/varnish-misc
