Disable reverse dns lookup

The BaseHTTPServer will do a reverse dns lookup when log message, which
will cause 10 seconds latency in some network environment. This will
significantly slow down the api request when wsgiref.simple_server is
used.

This patch creates a class, which inherits from
simple_server.WSGIRequestHandler but overrides address_string method,
and passes it to handler_class param of simple_server.make_server.

Change-Id: Ia38c7719ed700ab5867dcc4bcf3700bff282a907
Closes-Bug: #1291229

ceilometer/api/__init__.py

@@ -30,6 +30,12 @@ API_SERVICE_OPTS = [
                default='0.0.0.0',
                help='The listen IP for the ceilometer API server.',
                ),
+    cfg.BoolOpt('enable_reverse_dns_lookup',
+                default=False,
+                help=('Set it to False if your environment does not need '
+                      'or have dns server, otherwise it will delay the '
+                      'response from api.')
+                ),
 ]
 
 CONF = cfg.CONF

ceilometer/api/app.py

@@ -121,6 +121,21 @@ def get_server_cls(host):
     return server_cls
 
 
+def get_handler_cls():
+    cls = simple_server.WSGIRequestHandler
+
+    # old-style class doesn't support super
+    class CeilometerHandler(cls, object):
+        def address_string(self):
+            if cfg.CONF.api.enable_reverse_dns_lookup:
+                return super(CeilometerHandler, self).address_string()
+            else:
+                # disable reverse dns lookup, directly return ip adress
+                return self.client_address[0]
+
+    return CeilometerHandler
+
+
 def build_server():
     # Build the WSGI app
     root = VersionSelectorApplication()
@@ -128,7 +143,8 @@ def build_server():
     # Create the WSGI server and start it
     host, port = cfg.CONF.api.host, cfg.CONF.api.port
     server_cls = get_server_cls(host)
-    srv = simple_server.make_server(host, port, root, server_cls)
+    srv = simple_server.make_server(host, port, root,
+                                    server_cls, get_handler_cls())
 
     LOG.info(_('Starting server in PID %s') % os.getpid())
     LOG.info(_("Configuration:"))