Merge "tests: confirm that _output_hosts_file does not log too often" into stable/juno

neutron/agent/linux/dhcp.py

@@ -518,13 +518,13 @@ class Dnsmasq(DhcpLocalProcess):
         filename = self.get_conf_file_name('host')
 
         LOG.debug(_('Building host file: %s'), filename)
+        # NOTE(ihrachyshka): the loop should not log anything inside it, to
+        # avoid potential performance drop when lots of hosts are dumped
         for (port, alloc, hostname, name) in self._iter_hosts():
             if not alloc:
                 if getattr(port, 'extra_dhcp_opts', False):
                     buf.write('%s,%s%s\n' %
                               (port.mac_address, 'set:', port.id))
-                LOG.debug('Adding %(mac)s : set:%(tag)s',
-                          {"mac": port.mac_address, "tag": port.id})
                 continue
 
             # (dzyu) Check if it is legal ipv6 address, if so, need wrap
@@ -538,16 +538,9 @@ class Dnsmasq(DhcpLocalProcess):
                 buf.write('%s,%s,%s,%s%s\n' %
                           (port.mac_address, name, ip_address,
                            'set:', port.id))
-                LOG.debug('Adding %(mac)s : %(name)s : %(ip)s : '
-                          'set:%(tag)s',
-                          {"mac": port.mac_address, "name": name,
-                           "ip": ip_address, "tag": port.id})
             else:
                 buf.write('%s,%s,%s\n' %
                           (port.mac_address, name, ip_address))
-                LOG.debug('Adding %(mac)s : %(name)s : %(ip)s',
-                          {"mac": port.mac_address, "name": name,
-                           "ip": ip_address})
 
         utils.replace_file(filename, buf.getvalue())
         LOG.debug('Done building host file %s with contents:\n%s', filename,

neutron/tests/unit/test_linux_dhcp.py

@@ -1427,6 +1427,17 @@ tag:tag0,option:router""".lstrip()
                                 float(2.66))
             self.assertTrue(warning.called)
 
+    def test__output_hosts_file_log_only_twice(self):
+        dm = dhcp.Dnsmasq(self.conf, FakeDualStackNetworkSingleDHCP(),
+                          version=dhcp.Dnsmasq.MINIMUM_VERSION)
+        with mock.patch.object(dhcp.LOG, 'process') as process:
+            process.return_value = ('fake_message', {})
+            dm._output_hosts_file()
+        # The method logs twice, at the start of and the end. There should be
+        # no other logs, no matter how many hosts there are to dump in the
+        # file.
+        self.assertEqual(2, process.call_count)
+
     def test_only_populates_dhcp_enabled_subnets(self):
         exp_host_name = '/dhcp/eeeeeeee-eeee-eeee-eeee-eeeeeeeeeeee/host'
         exp_host_data = ('00:00:80:aa:bb:cc,host-192-168-0-2.openstacklocal,'