Implement stack event list --follow

This adds a --follow option which is similar to the --wait logging
behaviour in changes like I72421c1adf9220e3440179fec672f49803a6cde2
except that --follow doesn't exit until the user does ctrl-c.

This change also includes:
- always sort events ascending for all formatters - the newest events
  should always be at the bottom of the screen as they are generally the
  most interesting
- get_event marker handling tolerates the marker not being in the event
  list. --follow was triggering this, but ignoring the marker in this
  case has not lead to events being printed more than once

Change-Id: Ie0964918fc1d05e7e18aa39ceea6d4777deeb87e
Blueprint: heat-support-python-openstackclient

heatclient/common/event_utils.py

@@ -75,8 +75,11 @@ def get_events(hc, stack_id, event_args, nested_depth=0,
 
         # Slice the list if marker is specified
         if marker:
-            marker_index = [e.id for e in events].index(marker)
-            events = events[marker_index:]
+            try:
+                marker_index = [e.id for e in events].index(marker)
+                events = events[marker_index:]
+            except ValueError:
+                pass
 
         # Slice the list if limit is specified
         if limit:

heatclient/osc/v1/event.py

@@ -13,6 +13,7 @@
 #   Copyright 2015 IBM Corp.
 
 import logging
+import time
 
 from cliff import lister
 from cliff import show
@@ -134,6 +135,11 @@ class ListEvent(lister.Lister):
                    '(default: asc). Specify multiple times to sort on '
                    'multiple keys')
         )
+        parser.add_argument(
+            '--follow',
+            action='store_true',
+            help=_('Print events until process is halted')
+        )
         return parser
 
     def take_action(self, parsed_args):
@@ -149,6 +155,7 @@ class ListEvent(lister.Lister):
             'limit': parsed_args.limit,
             'marker': parsed_args.marker,
             'filters': heat_utils.format_parameters(parsed_args.filter),
+            'sort_dir': 'asc'
         }
 
         if parsed_args.resource and parsed_args.nested_depth:
@@ -165,6 +172,31 @@ class ListEvent(lister.Lister):
         else:
             nested_depth = 0
 
+        if parsed_args.follow:
+            if parsed_args.formatter != 'value':
+                msg = _('--follow can only be specified with --format value')
+                raise exc.CommandError(msg)
+
+            marker = parsed_args.marker
+            try:
+                while True:
+                    kwargs['marker'] = marker
+                    events = event_utils.get_events(
+                        client,
+                        stack_id=parsed_args.stack,
+                        event_args=kwargs,
+                        nested_depth=nested_depth,
+                        marker=marker)
+                    if events:
+                        marker = getattr(events[-1], 'id', None)
+                        events_log = heat_utils.event_log_formatter(events)
+                        self.app.stdout.write(events_log)
+                        self.app.stdout.write('\n')
+                    time.sleep(5)
+                    # this loop never exits
+            except (KeyboardInterrupt, EOFError):  # ctrl-c, ctrl-d
+                return [], []
+
         events = event_utils.get_events(
             client, stack_id=parsed_args.stack, event_args=kwargs,
             nested_depth=nested_depth, marker=parsed_args.marker,
@@ -175,7 +207,6 @@ class ListEvent(lister.Lister):
 
         if parsed_args.formatter == 'value':
             events = heat_utils.event_log_formatter(events).split('\n')
-            events.reverse()
             return [], [e.split(' ') for e in events]
 
         if len(events):

heatclient/tests/unit/osc/v1/test_event.py

@@ -111,6 +111,7 @@ class TestEventList(TestEvent):
         'limit': None,
         'marker': None,
         'filters': {},
+        'sort_dir': 'asc'
     }
 
     fields = ['resource_name', 'id', 'resource_status',
@@ -199,6 +200,31 @@ class TestEventList(TestEvent):
         self.event_client.list.assert_called_with(**self.defaults)
         self.assertEqual(self.fields, columns)
 
+    @mock.patch('time.sleep')
+    def test_event_list_follow(self, sleep):
+        sleep.side_effect = [None, KeyboardInterrupt()]
+        arglist = ['--follow', 'my_stack']
+        expected = (
+            '2015-11-13 10:02:17 [resource1]: '
+            'CREATE_COMPLETE  state changed\n'
+            '2015-11-13 10:02:17 [resource1]: '
+            'CREATE_COMPLETE  state changed\n'
+        )
+        parsed_args = self.check_parser(self.cmd, arglist, [])
+
+        columns, data = self.cmd.take_action(parsed_args)
+
+        defaults_with_marker = dict(self.defaults)
+        defaults_with_marker['marker'] = '1234'
+
+        self.event_client.list.assert_has_calls([
+            mock.call(**self.defaults),
+            mock.call(**defaults_with_marker)
+        ])
+        self.assertEqual([], columns)
+        self.assertEqual([], data)
+        self.assertEqual(expected, self.fake_stdout.make_string())
+
     def test_event_list_value_format(self):
         arglist = ['my_stack']
         expected = ('2015-11-13 10:02:17 [resource1]: CREATE_COMPLETE  '