Robustify attachment tracking in CinderFixtureNewAttachFlow

Cinder allows more than one attachment record on a non-multiattach
volume as long as only one attachment is "connected" (has a host
connector).

When you create an empty (no connector) attachment for an in-use
volume, the volume status changes to "attaching". If you try to
update the empty attachment before deleting the previous attachment,
Cinder will return a 400 like:

  Invalid volume: Volume b2aba195-6570-40c4-82bb-46d3557fceeb status
  must be available or downloading to reserve, but the current status
  is attaching.

This change refactors the attachment tracking in the
CinderFixtureNewAttachFlow fixture to be able to track the connector
per attachment and if code tries to update an attachment on an
already connected volume it will fail.

Change-Id: I369f82245465e96fc15d4fc71a79a8a71f6f2c6d

Author: mriedem

nova/tests/fixtures.py

@@ -1841,16 +1841,21 @@ def __init__(self, test):
         self.swap_volume_instance_uuid = None
         self.swap_volume_instance_error_uuid = None
         self.attachment_error_id = None
-        # A map of volumes to a list of (attachment_id, instance_uuid).
+        # A dict, keyed by volume id, to a dict, keyed by attachment id,
+        # with keys:
+        # - id: the attachment id
+        # - instance_uuid: uuid of the instance attached to the volume
+        # - connector: host connector dict; None if not connected
         # Note that a volume can have multiple attachments even without
         # multi-attach, as some flows create a blank 'reservation' attachment
-        # before deleting another attachment.
-        self.volume_to_attachment = collections.defaultdict(list)
+        # before deleting another attachment. However, a non-multiattach volume
+        # can only have at most one attachment with a host connector at a time.
+        self.volume_to_attachment = collections.defaultdict(dict)
 
     def volume_ids_for_instance(self, instance_uuid):
         for volume_id, attachments in self.volume_to_attachment.items():
-            for _, _instance_uuid in attachments:
-                if _instance_uuid == instance_uuid:
+            for attachment in attachments.values():
+                if attachment['instance_uuid'] == instance_uuid:
                     # we might have multiple volumes attached to this instance
                     # so yield rather than return
                     yield volume_id
@@ -1882,14 +1887,14 @@ def fake_get(self_api, context, volume_id, microversion=None):
                         else self.swap_volume_instance_error_uuid)
 
                     if attachments:
-                        attachment_id, instance_uuid = attachments[0]
+                        attachment = list(attachments.values())[0]
 
                         volume.update({
                             'status': 'in-use',
                             'attachments': {
                                 instance_uuid: {
                                     'mountpoint': '/dev/vdb',
-                                    'attachment_id': attachment_id
+                                    'attachment_id': attachment['id']
                                 }
                             },
                             'attach_status': 'attached'
@@ -1899,7 +1904,7 @@ def fake_get(self_api, context, volume_id, microversion=None):
             # Check to see if the volume is attached.
             if attachments:
                 # The volume is attached.
-                attachment_id, instance_uuid = attachments[0]
+                attachment = list(attachments.values())[0]
                 volume = {
                     'status': 'in-use',
                     'display_name': volume_id,
@@ -1908,8 +1913,8 @@ def fake_get(self_api, context, volume_id, microversion=None):
                     'multiattach': volume_id == self.MULTIATTACH_VOL,
                     'size': 1,
                     'attachments': {
-                        instance_uuid: {
-                            'attachment_id': attachment_id,
+                        attachment['instance_uuid']: {
+                            'attachment_id': attachment['id'],
                             'mountpoint': '/dev/vdb'
                         }
                     }
@@ -1953,14 +1958,13 @@ def _find_attachment(attachment_id):
             """Find attachment corresponding to ``attachment_id``.
 
             Returns:
-                A tuple of the volume ID, an attachment-instance mapping tuple
-                for the given attachment ID, and a list of attachment-instance
-                mapping tuples for the volume.
+                A tuple of the volume ID, an attachment dict
+                for the given attachment ID, and a dict (keyed by attachment
+                id) of attachment dicts for the volume.
             """
             for volume_id, attachments in self.volume_to_attachment.items():
-                for attachment in attachments:
-                    _attachment_id, instance_uuid = attachment
-                    if attachment_id == _attachment_id:
+                for attachment in attachments.values():
+                    if attachment_id == attachment['id']:
                         return volume_id, attachment, attachments
             raise exception.VolumeAttachmentNotFound(
                 attachment_id=attachment_id)
@@ -1971,8 +1975,10 @@ def fake_attachment_create(_self, context, volume_id, instance_uuid,
             if self.attachment_error_id is not None:
                 attachment_id = self.attachment_error_id
             attachment = {'id': attachment_id, 'connection_info': {'data': {}}}
-            self.volume_to_attachment[volume_id].append(
-                (attachment_id, instance_uuid))
+            self.volume_to_attachment[volume_id][attachment_id] = {
+                'id': attachment_id,
+                'instance_uuid': instance_uuid,
+                'connector': connector}
             LOG.info('Created attachment %s for volume %s. Total '
                      'attachments for volume: %d', attachment_id, volume_id,
                      len(self.volume_to_attachment[volume_id]))
@@ -1983,15 +1989,26 @@ def fake_attachment_delete(_self, context, attachment_id):
             # 'attachment' is a tuple defining a attachment-instance mapping
             volume_id, attachment, attachments = (
                 _find_attachment(attachment_id))
-            attachments.remove(attachment)
+            del attachments[attachment_id]
             LOG.info('Deleted attachment %s for volume %s. Total attachments '
                      'for volume: %d', attachment_id, volume_id,
                      len(attachments))
 
         def fake_attachment_update(_self, context, attachment_id, connector,
                                    mountpoint=None):
             # Ensure the attachment exists
-            _find_attachment(attachment_id)
+            volume_id, attachment, attachments = (
+                _find_attachment(attachment_id))
+            # Cinder will only allow one "connected" attachment per
+            # non-multiattach volume at a time.
+            if volume_id != self.MULTIATTACH_VOL:
+                for _attachment in attachments.values():
+                    if _attachment['connector'] is not None:
+                        raise exception.InvalidInput(
+                            'Volume %s is already connected with attachment '
+                            '%s on host %s' % (volume_id, _attachment['id'],
+                            _attachment['connector'].get('host')))
+            attachment['connector'] = connector
             LOG.info('Updating volume attachment: %s', attachment_id)
             attachment_ref = {'driver_volume_type': 'fake_type',
                               'id': attachment_id,