Add unique_key table constant and document it in the API

To facilitate database snap-shotting, we should standardize the way
unique_key is stored by the drivers.. This patch adds the expectation
to our DB API of how unique_key data can be accessed, extracted, and
restored.

Change-Id: I15c3c8d7b1b6aa257eebd8f11f9dbdd6eaa6bef5

dragonflow/cli/df_db.py

@@ -19,11 +19,12 @@ from dragonflow.cli import utils as cli_utils
 from dragonflow.common import exceptions as df_exceptions
 from dragonflow.common import utils as df_utils
 from dragonflow import conf as cfg
+from dragonflow.db import db_common
 from dragonflow.db import model_framework
 from dragonflow.db import models
 from dragonflow.db.models import all  # noqa
 
-db_tables = list(model_framework.iter_tables()) + ['unique_key']
+db_tables = list(model_framework.iter_tables()) + [db_common.UNIQUE_KEY_TABLE]
 
 
 def print_tables():

dragonflow/db/db_api.py

@@ -149,6 +149,10 @@ class DbApi(object):
     def allocate_unique_key(self, table):
         """Allocate a unique id in the controller
 
+        The allocation information should be managed in the 'unique_key'
+        table and stored by table name, s.t. the state can be extracted and
+        restored by get_key/set_ket calls.
+
         :table:       The name of resource table
         :returns:     Unique id
         """

dragonflow/db/db_common.py

@@ -16,6 +16,7 @@ from oslo_utils import timeutils
 
 SEND_ALL_TOPIC = 'D'
 DB_SYNC_MINIMUM_INTERVAL = 180
+UNIQUE_KEY_TABLE = 'unique_key'
 
 
 class DbUpdate(object):

dragonflow/db/drivers/cassandra_db_driver.py

@@ -18,12 +18,13 @@ from oslo_log import log
 from dragonflow.common import exceptions as df_exceptions
 from dragonflow import conf as cfg
 from dragonflow.db import db_api
+from dragonflow.db import db_common
 
 LOG = log.getLogger(__name__)
 
 ROOT_KS = 'openstack'
 
-CAS_TABLE = 'unique_key'
+CAS_TABLE = db_common.UNIQUE_KEY_TABLE
 
 # NOTE(nick-ma-z): http://datastax.github.io/python-driver/
 # api/cassandra.html

dragonflow/db/drivers/etcd_db_driver.py

@@ -21,6 +21,7 @@ from urllib3 import exceptions
 
 from dragonflow.common import exceptions as df_exceptions
 from dragonflow.db import db_api
+from dragonflow.db import db_common
 
 LOG = log.getLogger(__name__)
 
@@ -148,10 +149,10 @@ class EtcdDbDriver(db_api.DbApi):
         return res
 
     def _allocate_unique_key(self, table):
-        key = '/unique_key/%s' % table
+        key = self._make_key(db_common.UNIQUE_KEY_TABLE, table)
         prev_value = 0
         try:
-            prev_value = int(self.get_key('unique_key', table))
+            prev_value = int(self.get_key(db_common.UNIQUE_KEY_TABLE, table))
         except df_exceptions.DBKeyNotFound:
             if prev_value == 0:
                 # Create new key

dragonflow/db/drivers/ramcloud_db_driver.py

@@ -13,6 +13,7 @@
 import ramcloud
 
 from dragonflow.db import db_api
+from dragonflow.db import db_common
 
 
 class RamCloudDbDriver(db_api.DbApi):
@@ -77,7 +78,7 @@ class RamCloudDbDriver(db_api.DbApi):
         return res
 
     def _allocate_unique_key(self, table):
-        table_id = self.client.get_table_id('unique_key')
+        table_id = self.client.get_table_id(db_common.UNIQUE_KEY_TABLE)
         key = table
         while True:
             try:

dragonflow/db/drivers/redis_db_driver.py

@@ -18,6 +18,7 @@ from redis import exceptions
 
 from dragonflow.common import exceptions as df_exceptions
 from dragonflow.db import db_api
+from dragonflow.db import db_common
 from dragonflow.db.drivers import redis_mgt
 
 LOG = log.getLogger(__name__)
@@ -303,7 +304,7 @@ class RedisDbDriver(db_api.DbApi):
         return m.group(1)
 
     def _allocate_unique_key(self, table):
-        local_key = self._uuid_to_key('unique_key', table, None)
+        local_key = self._uuid_to_key(db_common.UNIQUE_KEY_TABLE, table, None)
         ip_port = None
         try:
             client = self._update_client(local_key)

dragonflow/db/drivers/rethink_db_driver.py

@@ -18,6 +18,7 @@ import rethinkdb as rdb
 from dragonflow.common import exceptions
 from dragonflow import conf as cfg
 from dragonflow.db import db_api
+from dragonflow.db import db_common
 
 _DF_DATABASE = 'dragonflow'
 
@@ -116,9 +117,10 @@ class RethinkDbDriver(db_api.DbApi):
             return [entry['id'] for entry in cursor]
 
     def allocate_unique_key(self, table_name):
-        self._ensure_table_exists('unique_key')
+        unique_key_table = db_common.UNIQUE_KEY_TABLE
+        self._ensure_table_exists(unique_key_table)
         with self._get_conn() as conn:
-            res = rdb.table('unique_key').get(table_name).replace(
+            res = rdb.table(unique_key_table).get(table_name).replace(
                 lambda post: {'id': table_name,
                               'key': post['key'].default(0).add(1)},
                 return_changes=True,

dragonflow/db/drivers/zookeeper_db_driver.py

@@ -19,6 +19,7 @@ import six
 from dragonflow.common import exceptions as df_exceptions
 from dragonflow.common import utils
 from dragonflow.db import db_api
+from dragonflow.db import db_common
 
 ROOT_NS = '/openstack'
 
@@ -163,7 +164,7 @@ class ZookeeperDbDriver(db_api.DbApi):
             raise df_exceptions.DBKeyNotFound(key=table)
 
     def _allocate_unique_key(self, table):
-        path = self._generate_path('unique_key', table)
+        path = self._generate_path(db_common.UNIQUE_KEY_TABLE, table)
 
         prev_value = 0
         while True: