Adds missing functions to ring.py, and more thorough tests.

Situation:
The function get_part_nodes is being called by Openstack-Swift's proxy/controllers/base.py:
        https://github.com/openstack/swift/blob/1.7.4/swift/proxy/controllers/base.py#L410
        https://github.com/openstack/swift/blob/1.7.6/swift/proxy/controllers/base.py#L447
As this was not implemented in the current GlusterFS version of ring.py, it was calling swift's
original get_part_nodes, which would often return the incorrect node, resulting in the incorrect
drive being associated with a request.
There is another function that the original ring.py implements -- get_other_nodes, which has to
do with replication.  Since GlusterFS is handling replication, this function should never be
called.  However, in the interest of completeness, that function is also being replaced.

Code changes:
The two functions, get_part_nodes, and get_other_nodes have been implemented to override the
default functions, and get_nodes has been updated to store information in self vars, about the
account being operated on, as the two new functions are not called with that info, and get_nodes
appears to always be called first.
The code has be refactored to all call _get_part_nodes, much like swift has refactored their code.

Reason for implementation this way:
I didn't see a better way to do it, but am open to suggestions.

Test cases:
A mock ring is created with two different devices, test and iops

test_first_device: Ensure that the first device, test, is returned for both get_nodes, and
        get_part_node, and get_more_nodes returns volume_not_in_ring.
test_invalid_device: Ensure that a request for a non-existant device returns volume_not_in_ring.
test_second_device: Same as test_first_device, but for the second device, iops instead of test.
test_second_device_with_reseller_prefix: Test that calling with the reseller prefix, AUTH_ will
        still return the correct data.

Change-Id: I2f3d526934a47b01e9c065d0edf0fbf06f300369
BUG: 924792
Signed-off-by: Alex Wheeler <wheelear@gmail.com>
Reviewed-on: http://review.gluster.org/4748
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Kaleb KEITHLEY <kkeithle@redhat.com>
Reviewed-by: Jeff Darcy <jdarcy@redhat.com>
Reviewed-by: Anand Avati <avati@redhat.com>

ufo/gluster/swift/common/ring.py

@@ -37,6 +37,29 @@ if not reseller_prefix.endswith('_'):
     reseller_prefix = reseller_prefix + '_'
 
 class Ring(ring.Ring):
+    def _get_part_nodes(self, part):
+        seen_ids = set()
+        nodes = [dev for dev in self._devs \
+                     if dev['device'] == self.acc_name \
+                     and not (dev['id'] in seen_ids \
+                                  or seen_ids.add(dev['id']))]
+        if not nodes:
+            nodes = [self.false_node]
+        return nodes
+
+    def get_part_nodes(self, part):
+        """
+        Get the nodes that are responsible for the partition. If one
+        node is responsible for more than one replica of the same
+        partition, it will only appear in the output once.
+
+        :param part: partition to get nodes for
+        :returns: list of node dicts
+
+        See :func:`get_nodes` for a description of the node dicts.
+        """
+        return self._get_part_nodes(part)
+
     def get_nodes(self, account, container=None, obj=None):
         """
         Get the partition and nodes for an account/container/object.
@@ -63,20 +86,26 @@ class Ring(ring.Ring):
                 hardware description
         ======  ===============================================================
         """
-        false_node = [{'zone': 1, 'weight': 100.0, 'ip': '127.0.0.1', 'id': 0, \
+        self.false_node = {'zone': 1, 'weight': 100.0, 'ip': '127.0.0.1', 'id': 0, \
                            'meta': '', 'device': 'volume_not_in_ring', \
-                           'port': 6012}]
+                           'port': 6012}
         if account.startswith(reseller_prefix):
-            acc_name = account.replace(reseller_prefix, '', 1)
+            self.acc_name = account.replace(reseller_prefix, '', 1)
         else:
-            acc_name = account
+            self.acc_name = account
 
         part = 0
-        seen_ids = set()
-        nodes = [dev for dev in self._devs \
-                     if dev['device'] == acc_name \
-                     and not (dev['id'] in seen_ids \
-                                  or seen_ids.add(dev['id']))]
-        if not nodes:
-            nodes = false_node
-        return part, nodes
+        return part, self._get_part_nodes(part)
+
+
+    def get_more_nodes(self, part):
+        """
+        Generator to get extra nodes for a partition for hinted handoff.
+
+        :param part: partition to get handoff nodes for
+        :returns: generator of node dicts
+
+        See :func:`get_nodes` for a description of the node dicts.
+        Should never be called in the swift UFO environment, so yield nothing
+        """
+        yield self.false_node

ufo/test/unit/common/test_ring.py

@@ -30,14 +30,52 @@ class TestRing(unittest.TestCase):
     def setUp(self):
         self.ring = Ring(SWIFT_DIR, ring_name='object')
 
-    def test_get_notes(self):
+    def test_first_device(self):
         try:
             __devs = self.ring._devs
             self.ring._devs = _mock_ring_data()
+
             part, node = self.ring.get_nodes('test')
             assert node[0]['device'] == 'test'
+            node = self.ring.get_part_nodes(0)
+            assert node[0]['device'] == 'test'
+            for node in self.ring.get_more_nodes(0):
+                assert node['device'] == 'volume_not_in_ring'
+        finally:
+            self.ring._devs = __devs
+
+    def test_invalid_device(self):
+        try:
+            __devs = self.ring._devs
+            self.ring._devs = _mock_ring_data()
+
             part, node = self.ring.get_nodes('test2')
-            assert node
+            assert node[0]['device'] == 'volume_not_in_ring'
+            node = self.ring.get_part_nodes(0)
             assert node[0]['device'] == 'volume_not_in_ring'
         finally:
             self.ring._devs = __devs
+
+    def test_second_device(self):
+        try:
+            __devs = self.ring._devs
+            self.ring._devs = _mock_ring_data()
+
+            part, node = self.ring.get_nodes('iops')
+            assert node[0]['device'] == 'iops'
+            node = self.ring.get_part_nodes(0)
+            assert node[0]['device'] == 'iops'
+            for node in self.ring.get_more_nodes(0):
+                assert node['device'] == 'volume_not_in_ring'
+        finally:
+            self.ring._devs = __devs
+
+    def test_second_device_with_reseller_prefix(self):
+        try:
+            __devs = self.ring._devs
+            self.ring._devs = _mock_ring_data()
+
+            part, node = self.ring.get_nodes('AUTH_iops')
+            assert node[0]['device'] == 'iops'
+        finally:
+            self.ring._devs = __devs