Initializing a longer resource id in DB2 nosql backend

Longer resource id is reqpured by compute node's resource as their
id is '<hostname>_<nodename>'. DB2 creates a VARCHAR(70) for
resource id when its length < 70. But DB2 can create a VARCHAR(n)
for the resource id which has n(n>70) characters. This patch adds
an option 'db2nosql_resource_id_maxlen'(default is 512) to allow
user to adjust the value for their ENV.

@DocImpact

Change-Id: Ib58cfffb238d3b818831f0ccfe4659cfcf9c3c8a
Closes-Bug: #1387532

ceilometer/storage/__init__.py

@@ -63,6 +63,11 @@ OPTS = [
                help='The name of the replica set which is used to connect to '
                     'MongoDB database. If it is set, MongoReplicaSetClient '
                     'will be used instead of MongoClient.'),
+    cfg.IntOpt('db2nosql_resource_id_maxlen',
+               default=512,
+               help="The max length of resources id in DB2 nosql, "
+                    "the value should be larger than len(hostname) * 2 "
+                    "as compute node's resource id is <hostname>_<nodename>."),
 ]
 
 cfg.CONF.register_opts(OPTS, group='database')

ceilometer/storage/impl_db2.py

@@ -28,6 +28,7 @@ import sys
 
 import bson.code
 import bson.objectid
+from oslo.config import cfg
 from oslo.utils import timeutils
 import pymongo
 import six
@@ -159,7 +160,14 @@ class Connection(pymongo_base.Connection):
         # queries, so the database won't take advantage of an index
         # including both.
         if self.db.resource.index_information() == {}:
-            resource_id = str(bson.objectid.ObjectId())
+            # Initializing a longer resource id to workaround DB2 nosql issue.
+            # Longer resource id is required by compute node's resource as
+            # their id is '<hostname>_<nodename>'. DB2 creates a VARCHAR(70)
+            # for resource id when its length < 70. But DB2 can create a
+            # VARCHAR(n) for the resource id which has n(n>70) characters.
+            # Users can adjust 'db2nosql_resource_id_maxlen'(default is 512)
+            # for their ENV.
+            resource_id = 'x' * cfg.CONF.database.db2nosql_resource_id_maxlen
             self.db.resource.insert({'_id': resource_id,
                                      'no_key': resource_id})
             meter_id = str(bson.objectid.ObjectId())

ceilometer/tests/storage/test_impl_db2.py

@@ -26,8 +26,12 @@
 from ceilometer.alarm.storage import impl_db2 as impl_db2_alarm
 from ceilometer.event.storage import impl_db2 as impl_db2_event
 from ceilometer.storage import impl_db2
+from ceilometer.storage.mongo import utils as pymongo_utils
 from ceilometer.tests import base as test_base
 
+import mock
+from oslo.config import cfg
+
 
 class CapabilitiesTest(test_base.BaseTestCase):
     # Check the returned capabilities list, which is specific to each DB
@@ -92,3 +96,20 @@ class CapabilitiesTest(test_base.BaseTestCase):
         }
         actual_capabilities = impl_db2.Connection.get_storage_capabilities()
         self.assertEqual(expected_capabilities, actual_capabilities)
+
+
+class ConnectionTest(test_base.BaseTestCase):
+    @mock.patch.object(pymongo_utils.ConnectionPool, 'connect')
+    def test_upgrade(self, mongo_connect):
+        conn_mock = mock.MagicMock()
+        conn_mock.server_info.return_value = {}
+        conn_mock.ceilodb2.resource.index_information.return_value = {}
+        mongo_connect.return_value = conn_mock
+        cfg.CONF.set_override('db2nosql_resource_id_maxlen',
+                              256,
+                              group='database')
+        impl_db2.Connection('db2://user:pwd@localhost:27017/ceilodb2')
+        resource_id = 'x' * 256
+        conn_mock.ceilodb2.resource.insert.assert_called_with(
+            {'_id': resource_id,
+             'no_key': resource_id})