[6.0] 6f14d2ed4 shard director: explain how the ring is constructed with weights

[Reza Naghibi]

commit 6f14d2ed4236096be8eefa411c145f085d92f4f2
Author: Nils Goroll <nils.goroll at uplex.de>
Date:   Mon Jul 6 18:07:09 2020 +0200

    shard director: explain how the ring is constructed with weights
    
     Conflicts:
            lib/libvmod_directors/vmod.vcc

diff --git a/lib/libvmod_directors/vmod.vcc b/lib/libvmod_directors/vmod.vcc
index de467ee27..f79424e93 100644
--- a/lib/libvmod_directors/vmod.vcc
+++ b/lib/libvmod_directors/vmod.vcc
@@ -307,7 +307,9 @@ structure gets built from the last 32 bits of SHA256 hash values of
 `<ident>`\ `<n>` (default `ident` being the backend name) for each
 backend and for a running number `n` from 1 to `replicas`. Hashing
 creates the seemingly random order for placement of backends on the
-consistent hashing ring.
+consistent hashing ring.  When ``.add_backend()`` is called with a
+weight argument, replicas is scaled by that weight to add
+proportionally more copies of the that backend on the ring.
 
 When ``.backend()`` is called, a load balancing key gets generated
 unless provided. The smallest hash value in the circle is looked up