The "miss" portion of a request in Varnish

varnish-miss-path-simple

sub vcl_recv {
    
    # Set the backend for the request if it should miss the cache.

    set req.backend = backend;
    
    # Send the request along to the cache lookup.

    return(lookup);
}

sub vcl_miss {

    # You can have conditional logic here, but for now, let's just fetch from the backend.

    return(fetch);
}

sub vcl_fetch {

    # Fetching an object from the backend will also place it in the cache, usually.
    # Set a 1 hour cache lifetime on this object that we're fetching from the backend.

    set beresp.ttl = 1h;
        
    # Set this backend request as cacheable. 

    set beresp.http.X-Cacheable = "YES";
    
    # Turn off the Vary header.
    # Some backends (*cough* Django *cough*) will set a header based on the User-Agent 
    # of the request. Varnish will cache a different version of the page for every 
    # single variation of User-Agent that visits your site. This is very bad. So we  
    # strip the Vary header off before delivering the request to the cache.

    unset beresp.http.Vary;
    
    # Deliver the object to the cache.

    return(deliver);
}

sub vcl_deliver {

    # Now, deliver the result to the browser.

    return(deliver);
}