add a little chapter on instrumentation

README.rst

@@ -137,6 +137,14 @@ servers as the nameservers for zone delegation, and the other nodes
 are free to have dynamic membership.
 
 
+Instrumentation
++++++++++++++++
+
+The ``redirectord`` daemon exports statistics on served queries (along
+with data on its own memory usage), in JSON format at the
+``/debug/vars`` URL.
+
+
 
 .. _etcd: https://github.com/coreos/etcd
-.. _autoca: https://git.autistici.org/public/projects/ai/autoca
+.. _autoca: https://git.autistici.org/ai/autoca