wsgi server: fix default address and restore address family

Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>

Author: martinetd

prometheus_client/exposition.py

@@ -149,11 +149,13 @@ def _get_best_family(address, port):
     return family, sockaddr[0]
 
 
-def start_wsgi_server(port, addr='', registry=REGISTRY):
+def start_wsgi_server(port, addr='0.0.0.0', registry=REGISTRY):
     """Starts a WSGI server for prometheus metrics as a daemon thread."""
     app = make_wsgi_app(registry)
+    old_family = ThreadingWSGIServer.address_family
     ThreadingWSGIServer.address_family, addr = _get_best_family(addr, port)
     httpd = make_server(addr, port, app, ThreadingWSGIServer, handler_class=_SilentHandler)
+    ThreadingWSGIServer.address_family = old_family
     t = threading.Thread(target=httpd.serve_forever)
     t.daemon = True
     t.start()