Add warning when CAS paths are skipped and ensure we are under a transaction

data/database.py

@@ -7,6 +7,7 @@ import sys
 import time
 import uuid
 
+from contextlib import contextmanager
 from collections import defaultdict
 from datetime import datetime
 from random import SystemRandom
@@ -230,6 +231,7 @@ db_match_func = CallableProxy()
 db_for_update = CallableProxy()
 db_transaction = CallableProxy()
 db_concat_func = CallableProxy()
+ensure_under_transaction = CallableProxy()
 
 
 def validate_database_url(url, db_kwargs, connect_timeout=5):
@@ -286,7 +288,16 @@ def configure(config_object):
   def _db_transaction():
     return config_object['DB_TRANSACTION_FACTORY'](db)
 
+  @contextmanager
+  def _ensure_under_transaction():
+    if not config_object['TESTING']:
+      if db.transaction_depth() == 0:
+        raise Exception('Expected to be under a transaction')
+
+    yield
+
   db_transaction.initialize(_db_transaction)
+  ensure_under_transaction.initialize(_ensure_under_transaction)
 
 def random_string_generator(length=16):
   def random_string():

data/model/storage.py

@@ -8,7 +8,8 @@ from data.model import (config, db_transaction, InvalidImageException, TorrentIn
                         DataModelException, _basequery)
 from data.database import (ImageStorage, Image, ImageStoragePlacement, ImageStorageLocation,
                            ImageStorageTransformation, ImageStorageSignature,
-                           ImageStorageSignatureKind, Repository, Namespace, TorrentInfo)
+                           ImageStorageSignatureKind, Repository, Namespace, TorrentInfo,
+                           ensure_under_transaction)
 
 
 logger = logging.getLogger(__name__)
@@ -83,6 +84,7 @@ def garbage_collect_storage(storage_id_whitelist):
     """ Returns the list of paths to remove from storage, filtered from the given placements
         query by removing any CAS paths that are still referenced by storage(s) in the database.
     """
+    with ensure_under_transaction():
       if not placements_list:
         return set()
 
@@ -97,6 +99,10 @@ def garbage_collect_storage(storage_id_whitelist):
                  .select(ImageStorage.content_checksum)
                  .where(ImageStorage.content_checksum << list(content_checksums)))
         referenced_checksums = set([image_storage.content_checksum for image_storage in query])
+        if referenced_checksums:
+          logger.warning('GC attempted to remove CAS checksums %s, which are still referenced',
+                         referenced_checksums)
+
         unreferenced_checksums = content_checksums - referenced_checksums
 
       # Return all placements for all image storages found not at a CAS path or with a content