When varnish logs a Hit entry (SLT_Hit), it means the
vcl_recv() function has given a go for serving the request
from cache and the object is available.
This however doesn't guarantee that our request was served
from the cache. The default vcl_hit() code (man vcl)
checks that the object has to be cacheable too, at least
on varnish 2.1.
if (!obj.cacheable) {
return(pass)
}
vcl_hit() could still return pass, in which case
the request is definitely a miss.