storage: define interface for backends and check they implement it

neo/lib/interfaces.py

+#
+# Copyright (C) 2015  Nexedi SA
+#
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License
+# as published by the Free Software Foundation; either version 2
+# of the License, or (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+import inspect
+from functools import wraps
+
+def implements(obj, ignore=()):
+    tobj = type(obj)
+    ignore = set(ignore)
+    not_implemented = []
+    for name in dir(obj):
+        method = getattr(obj if issubclass(tobj, type) or name in obj.__dict__
+                             else tobj, name)
+        if inspect.ismethod(method):
+            try:
+                method.__abstract__
+                ignore.remove(name)
+            except KeyError:
+                not_implemented.append(name)
+            except AttributeError:
+                not_implemented.extend(func.__name__
+                    for func in getattr(method, "__requires__", ())
+                    if not hasattr(obj, func.__name__))
+    assert not ignore, ignore
+    assert not not_implemented, not_implemented
+    return obj
+
+def _set_code(func):
+    args, varargs, varkw, _ = inspect.getargspec(func)
+    if varargs:
+        args.append("*" + varargs)
+    if varkw:
+        args.append("**" + varkw)
+    exec "def %s(%s): raise NotImplementedError\nf = %s" % (
+        func.__name__, ",".join(args), func.__name__)
+    func.func_code = f.func_code
+
+def abstract(func):
+    _set_code(func)
+    func.__abstract__ = 1
+    return func
+
+def requires(*args):
+    for func in args:
+        _set_code(func)
+    def decorator(func):
+        func.__requires__ = args
+        return func
+    return decorator

neo/storage/database/__init__.py

@@ -17,7 +17,6 @@
 LOG_QUERIES = False
 
 from neo.lib.exception import DatabaseFailure
-from .manager import DatabaseManager
 
 DATABASE_MANAGER_DICT = {
     'Importer': 'importer.ImporterDatabaseManager',

neo/storage/database/importer.py

@@ -23,10 +23,13 @@ from ConfigParser import SafeConfigParser
 from ZODB.config import storageFromString
 from ZODB.POSException import POSKeyError
 
-from . import buildDatabaseManager, DatabaseManager
+from . import buildDatabaseManager
+from .manager import DatabaseManager
 from neo.lib import logging, patch, util
 from neo.lib.exception import DatabaseFailure
-from neo.lib.protocol import CellStates, ZERO_OID, ZERO_TID, ZERO_HASH, MAX_TID
+from neo.lib.interfaces import implements
+from neo.lib.protocol import BackendNotImplemented, CellStates, \
+    MAX_TID, ZERO_HASH, ZERO_OID, ZERO_TID
 
 patch.speedupFileStorageTxnLookup()
 
@@ -280,6 +283,9 @@ class ImporterDatabaseManager(DatabaseManager):
     def __init__(self, *args, **kw):
         super(ImporterDatabaseManager, self).__init__(*args, **kw)
         self.db._connect()
+        implements(self, """_getNextTID checkSerialRange checkTIDRange
+            deleteObject deleteTransaction dropPartitions getLastTID
+            getReplicationObjectList getTIDList nonempty""".split())
 
     _uncommitted_data = property(
         lambda self: self.db._uncommitted_data,
@@ -549,3 +555,8 @@ class ImporterDatabaseManager(DatabaseManager):
                                                    length, partition)
         return r
 
+    def getObjectHistory(self, *args, **kw):
+        raise BackendNotImplemented(self.getObjectHistory)
+
+    def pack(self, *args, **kw):
+        raise BackendNotImplemented(self.pack)

neo/storage/database/mysqldb.py

@@ -28,10 +28,11 @@ import string
 import struct
 import time
 
-from . import DatabaseManager, LOG_QUERIES
-from .manager import CreationUndone, splitOIDField
+from . import LOG_QUERIES
+from .manager import CreationUndone, DatabaseManager, splitOIDField
 from neo.lib import logging, util
 from neo.lib.exception import DatabaseFailure
+from neo.lib.interfaces import implements
 from neo.lib.protocol import CellStates, ZERO_OID, ZERO_TID, ZERO_HASH
 
 
@@ -40,6 +41,7 @@ def getPrintableQuery(query, max=70):
         else '\\x%02x' % ord(c) for c in query)
 
 
+@implements
 class MySQLDatabaseManager(DatabaseManager):
     """This class manages a database on MySQL."""
 

neo/storage/database/sqlite.py

@@ -20,10 +20,11 @@ from hashlib import sha1
 import string
 import traceback
 
-from . import DatabaseManager, LOG_QUERIES
-from .manager import CreationUndone, splitOIDField
+from . import LOG_QUERIES
+from .manager import CreationUndone, DatabaseManager, splitOIDField
 from neo.lib import logging, util
 from neo.lib.exception import DatabaseFailure
+from neo.lib.interfaces import implements
 from neo.lib.protocol import CellStates, ZERO_OID, ZERO_TID, ZERO_HASH
 
 def unique_constraint_message(table, *columns):
@@ -57,6 +58,7 @@ def retry_if_locked(f, *args):
                     raise
 
 
+@implements
 class SQLiteDatabaseManager(DatabaseManager):
     """This class manages a database on SQLite.