Add a --limit parameter to list operations

In v2, we use the link header during paginations to know when there are
more images available in the server that could be returned in the same
request. This way, it's possible to iterate over the generator returned
by list and consume the images in the server.

However, it's currently not possible to tell glanceclient the exact
number of images we want, which basically means that it'll *always* go
through the whole list of images in the server unless the limit is
implemented by the consumer.

DocImpact
Change-Id: I9f65a40d4eafda6320e5c7d94d03fcd1bbc93e33
Closes-bug: #1415035

glanceclient/v2/images.py

@@ -46,7 +46,19 @@ class Controller(object):
         ori_validate_fun = self.model.validate
         empty_fun = lambda *args, **kwargs: None
 
-        def paginate(url):
+        limit = kwargs.get('limit')
+        # NOTE(flaper87): Don't use `get('page_size', DEFAULT_SIZE)` otherwise,
+        # it could be possible to send invalid data to the server by passing
+        # page_size=None.
+        page_size = kwargs.get('page_size') or DEFAULT_PAGE_SIZE
+
+        def paginate(url, page_size, limit=None):
+
+            if limit and page_size > limit:
+                # NOTE(flaper87): Avoid requesting 2000 images when limit is 1
+                url = url.replace("limit=%s" % page_size,
+                                  "limit=%s" % limit)
+
             resp, body = self.http_client.get(url)
             for image in body['images']:
                 # NOTE(bcwaldon): remove 'self' for now until we have
@@ -60,6 +72,11 @@ class Controller(object):
                 # image entry for each page.
                 self.model.validate = empty_fun
 
+                if limit:
+                    limit -= 1
+                    if limit <= 0:
+                        raise StopIteration
+
             # NOTE(zhiyan); Reset validation function.
             self.model.validate = ori_validate_fun
 
@@ -68,15 +85,13 @@ class Controller(object):
             except KeyError:
                 return
             else:
-                for image in paginate(next_url):
+                for image in paginate(next_url, page_size, limit):
                     yield image
 
         filters = kwargs.get('filters', {})
-
+        # NOTE(flaper87): We paginate in the client, hence we use
-        if not kwargs.get('page_size'):
+        # the page_size as Glance's limit.
-            filters['limit'] = DEFAULT_PAGE_SIZE
+        filters['limit'] = page_size
-        else:
-            filters['limit'] = kwargs['page_size']
 
         tags = filters.pop('tag', [])
         tags_url_params = []
@@ -94,7 +109,7 @@ class Controller(object):
         for param in tags_url_params:
             url = '%s&%s' % (url, parse.urlencode(param))
 
-        for image in paginate(url):
+        for image in paginate(url, page_size, limit):
             yield image
 
     def get(self, image_id):

glanceclient/v2/shell.py

@@ -107,6 +107,8 @@ def do_image_update(gc, args):
     utils.print_image(image)
 
 
+@utils.arg('--limit', metavar='<LIMIT>', default=None, type=int,
+           help='Maximum number of images to get.')
 @utils.arg('--page-size', metavar='<SIZE>', default=None, type=int,
            help='Number of images to request in each paginated request.')
 @utils.arg('--visibility', metavar='<VISIBILITY>',
@@ -135,6 +137,8 @@ def do_image_list(gc, args):
     filters = dict([item for item in filter_items if item[1] is not None])
 
     kwargs = {'filters': filters}
+    if args.limit is not None:
+        kwargs['limit'] = args.page_size
     if args.page_size is not None:
         kwargs['page_size'] = args.page_size
 

tests/v2/test_images.py

@@ -78,6 +78,25 @@ data_fixtures = {
             ]},
         ),
     },
+    '/v2/images?limit=2': {
+        'GET': (
+            {},
+            {
+                'images': [
+                    {
+                        'id': '3a4560a1-e585-443e-9b39-553b46ec92d1',
+                        'name': 'image-1',
+                    },
+                    {
+                        'id': '6f99bf80-2ee6-47cf-acfe-1f1fabb7e810',
+                        'name': 'image-2',
+                    },
+                ],
+                'next': ('/v2/images?limit=2&'
+                         'marker=6f99bf80-2ee6-47cf-acfe-1f1fabb7e810'),
+            },
+        ),
+    },
     '/v2/images?limit=1': {
         'GET': (
             {},
@@ -104,6 +123,17 @@ data_fixtures = {
             ]},
         ),
     },
+    ('/v2/images?limit=1&marker=6f99bf80-2ee6-47cf-acfe-1f1fabb7e810'): {
+        'GET': (
+            {},
+            {'images': [
+                {
+                    'id': '3f99bf80-2ee6-47cf-acfe-1f1fabb7e811',
+                    'name': 'image-3',
+                },
+            ]},
+        ),
+    },
     '/v2/images/3a4560a1-e585-443e-9b39-553b46ec92d1': {
         'GET': (
             {},
@@ -420,6 +450,17 @@ class TestController(testtools.TestCase):
         self.assertEqual('6f99bf80-2ee6-47cf-acfe-1f1fabb7e810', images[1].id)
         self.assertEqual('image-2', images[1].name)
 
+    def test_list_images_paginated_with_limit(self):
+        # NOTE(bcwaldon):cast to list since the controller returns a generator
+        images = list(self.controller.list(limit=3, page_size=2))
+        self.assertEqual('3a4560a1-e585-443e-9b39-553b46ec92d1', images[0].id)
+        self.assertEqual('image-1', images[0].name)
+        self.assertEqual('6f99bf80-2ee6-47cf-acfe-1f1fabb7e810', images[1].id)
+        self.assertEqual('image-2', images[1].name)
+        self.assertEqual('3f99bf80-2ee6-47cf-acfe-1f1fabb7e811', images[2].id)
+        self.assertEqual('image-3', images[2].name)
+        self.assertEqual(3, len(images))
+
     def test_list_images_visibility_public(self):
         filters = {'filters': {'visibility': 'public'}}
         images = list(self.controller.list(**filters))

tests/v2/test_shell_v2.py

@@ -61,6 +61,7 @@ class ShellV2Test(testtools.TestCase):
 
     def test_do_image_list(self):
         input = {
+            'limit': None,
             'page_size': 18,
             'visibility': True,
             'member_status': 'Fake',
@@ -88,6 +89,7 @@ class ShellV2Test(testtools.TestCase):
 
     def test_do_image_list_with_property_filter(self):
         input = {
+            'limit': None,
             'page_size': 1,
             'visibility': True,
             'member_status': 'Fake',