Varnish with multiple hosts/subdomains

cachevarnish

I'm new to Varnish, and I'm hoping it already does this "out of the box", but I'd like to clarify before I consider using it in production:

Here's my setup:

  1. I have multiple sites running off of the same machine that vary by subdomain (i.e. user1.example.com, user2.example.com, etc.)
  2. Each "site" has a profile picture that has the same name (i.e. user1.example.com/profile.png, user2.example.com/profile.png)

Will Varnish recognize these as separate resources and cache them accordingly? Or will I need to change something in the VCL to tell it include the full host url when looking up cache hits?

Best Answer

They will be cached separately out of the box.

The default code for vcl_hash is what controls this:

sub vcl_hash {
    set req.hash += req.url;
    if (req.http.host) {
        set req.hash += req.http.host;
    } else {
        set req.hash += server.ip;
    }
    return (hash);
}

As you can see, the hostname is included in the hash if it exists, and if it doesn't, the IP of the server is included.

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