use TTLs with member listing to keep a current list of cluster members

governor.py

@@ -68,4 +68,6 @@ while True:
             if member != postgresql.name:
                 postgresql.query("DO LANGUAGE plpgsql $$DECLARE somevar VARCHAR; BEGIN SELECT slot_name INTO somevar FROM pg_replication_slots WHERE slot_name = '%(slot)s' LIMIT 1; IF NOT FOUND THEN PERFORM pg_create_physical_replication_slot('%(slot)s'); END IF; END$$;" % {"slot": member})
 
+    etcd.touch_member(postgresql.name, postgresql.connection_string)
+
     time.sleep(config["loop_wait"])

helpers/etcd.py

@@ -66,7 +66,7 @@ class Etcd:
             raise helpers.errors.CurrentLeaderError("Etcd is not responding properly")
 
     def touch_member(self, member, connection_string):
-        self.put_client_path("/members/%s" % member, {"value": connection_string})
+        self.put_client_path("/members/%s" % member, {"value": connection_string, "ttl": self.ttl})
 
     def take_leader(self, value):
         return self.put_client_path("/leader", {"value": value, "ttl": self.ttl}) == None