feat(api): GET and HEAD methods on queue

To allow

    GET/HEAD /queues/a-queue

gives users an intuitive approach to test whether the queue exits,
while the URI above is returned as the Location header by a queue's
PUT method.

Implements: blueprint queue-get-and-head
Fixes: bug #1207075

Change-Id: Iefd3236a739b1a5d959efb489fc2b966ee893599

marconi/storage/base.py

@@ -113,7 +113,7 @@ class QueueBase(ControllerBase):
 
     @abc.abstractmethod
     def create(self, name, project=None):
-        """Base method for queue creation
+        """Base method for queue creation.
 
         :param name: The queue name
         :param project: Project id
@@ -122,6 +122,17 @@ class QueueBase(ControllerBase):
         """
         raise NotImplementedError
 
+    @abc.abstractmethod
+    def exists(self, name, project=None):
+        """Base method for testing queue existence.
+
+        :param name: The queue name
+        :param project: Project id
+        :returns: True if a queue exists and False
+            if it does not.
+        """
+        raise NotImplementedError
+
     @abc.abstractmethod
     def set_metadata(self, name, metadata, project=None):
         """Base method for updating a queue metadata.

marconi/storage/mongodb/queues.py

@@ -122,6 +122,10 @@ class QueueController(storage.QueueBase):
         else:
             return True
 
+    @utils.raises_conn_error
+    def exists(self, name, project=None):
+        return self._col.find_one({'p': project, 'n': name}) is not None
+
     @utils.raises_conn_error
     def set_metadata(self, name, metadata, project=None):
         rst = self._col.update({'p': project, 'n': name},

marconi/storage/sqlite/queues.py

@@ -95,6 +95,15 @@ class QueueController(base.QueueBase):
 
         return self.driver.affected
 
+    def exists(self, name, project):
+        if project is None:
+            project = ''
+
+        return self.driver.run('''
+            select id from Queues
+             where project = ? and name = ?
+        ''', project, name).fetchone() is not None
+
     def set_metadata(self, name, metadata, project):
         if project is None:
             project = ''

marconi/tests/storage/base.py

@@ -75,6 +75,9 @@ class QueueControllerTest(ControllerBaseTest):
         created = self.controller.create('test', project=self.project)
         self.assertTrue(created)
 
+        # Test Queue Existence
+        self.assertTrue(self.controller.exists('test', project=self.project))
+
         # Test Queue retrieval
         metadata = self.controller.get_metadata('test', project=self.project)
         self.assertEqual(metadata, {})
@@ -103,6 +106,9 @@ class QueueControllerTest(ControllerBaseTest):
         # Test Queue Deletion
         self.controller.delete('test', project=self.project)
 
+        # Test Queue Existence
+        self.assertFalse(self.controller.exists('test', project=self.project))
+
         # Test DoesNotExist Exception
         with testing.expect(storage.exceptions.DoesNotExist):
             self.controller.get_metadata('test', project=self.project)

marconi/tests/transport/wsgi/test_queue_lifecycle.py

@@ -48,9 +48,9 @@ class QueueLifecycleBaseTest(base.TestBase):
             location = ('Location', '/v1/queues/gumshoe')
             self.assertIn(location, self.srmock.headers)
 
-            # Get on queues shouldn't work any more
-            self.simulate_get(path, project_id)
-            self.assertEquals(self.srmock.status, falcon.HTTP_405)
+            # Ensure queue existence
+            self.simulate_head(path, project_id)
+            self.assertEquals(self.srmock.status, falcon.HTTP_204)
 
             # Add metadata
             doc = '{"messages": {"ttl": 600}}'
@@ -67,6 +67,10 @@ class QueueLifecycleBaseTest(base.TestBase):
             self.simulate_delete(path, project_id)
             self.assertEquals(self.srmock.status, falcon.HTTP_204)
 
+            # Get non-existent queue
+            self.simulate_get(path, project_id)
+            self.assertEquals(self.srmock.status, falcon.HTTP_404)
+
             # Get non-existent stats
             self.simulate_get(path + '/stats', project_id)
             self.assertEquals(self.srmock.status, falcon.HTTP_404)

marconi/tests/util/faulty_storage.py

@@ -44,6 +44,9 @@ class QueueController(storage.QueueBase):
     def create(self, name, project=None):
         raise NotImplementedError()
 
+    def exists(self, name, project=None):
+        raise NotImplementedError()
+
     def set_metadata(self, name, metadata, project=None):
         raise NotImplementedError()
 

marconi/transport/wsgi/queues.py

@@ -49,6 +49,21 @@ class ItemResource(object):
         resp.status = falcon.HTTP_201 if created else falcon.HTTP_204
         resp.location = req.path
 
+    def on_head(self, req, resp, project_id, queue_name):
+        LOG.debug(_("Queue item exists - queue: %(queue)s, "
+                    "project: %(project)s") %
+                  {"queue": queue_name, "project": project_id})
+
+        if self.queue_controller.exists(queue_name,
+                                        project=project_id):
+            resp.status = falcon.HTTP_204
+        else:
+            resp.status = falcon.HTTP_404
+
+        resp.content_location = req.path
+
+    on_get = on_head
+
     def on_delete(self, req, resp, project_id, queue_name):
         LOG.debug(_("Queue item DELETE - queue: %(queue)s, "
                     "project: %(project)s") %