add winery backend

Related to: #3432

Test Plan

tox

---

Migrated from D6006 (view on Phabricator)

swh/objstorage/backends/winery/__init__.py

+# Copyright (C) 2021  The Software Heritage developers
+# See the AUTHORS file at the top-level directory of this distribution
+# License: GNU General Public License version 3, or any later version
+# See top-level LICENSE file for more information
+
+import abc
+
+from swh.objstorage.exc import Error, ObjNotFoundError
+from swh.objstorage.objstorage import ObjStorage, compute_hash
+
+
+class WineryObjStorageDriver(object):
+    pass
+
+
+class WineryObjStorage(ObjStorage, metaclass=abc.ABCMeta):
+    """ObjStorage that connect to a winery object storage
+
+    https://wiki.softwareheritage.org/wiki/A_practical_approach_to_efficiently_store_100_billions_small_objects_in_Ceph
+
+    Args:
+      kwargs: extra arguments are passed through to the winery
+    """
+
+    def __init__(
+        self, **kwargs,
+    ):
+        super().__init__(**kwargs)
+        self.driver = WineryObjStorageDriver()
+
+    def check_config(self, *, check_write):
+        return True
+
+    def __contains__(self, obj_id, *args, **kwargs):
+        return obj_id in self.driver
+
+    def add(self, content, obj_id=None, check_presence=True, *args, **kwargs):
+        if check_presence is True:
+            if obj_id in self.driver:
+                return obj_id
+        if obj_id is None:
+            obj_id = compute_hash(content)
+        self.driver[obj_id] = content
+        return obj_id
+
+    def get(self, obj_id, *args, **kwargs):
+        if obj_id not in self.driver:
+            raise ObjNotFoundError(obj_id)
+        return self.driver[obj_id]
+
+    def check(self, obj_id, *args, **kwargs):
+        if obj_id not in self.driver:
+            raise ObjNotFoundError(obj_id)
+        if obj_id != compute_hash(self.driver[obj_id]):
+            raise Error(obj_id)
+
+    def delete(self, obj_id, *args, **kwargs):
+        super().delete(obj_id)  # Check delete permission
+        if obj_id not in self.driver:
+            raise ObjNotFoundError(obj_id)
+        del self.driver[obj_id]
+        return True
+
+    def __iter__(self):
+        for k in sorted(self.driver.keys()):
+            yield k

[vlorentz]

that's implicit in py3 ;)

[Loïc Dachary]

True. It shows in other places therefore I figured it's tolerated :-)