Improve the garbage collection tests.

data/model/repository.py

@@ -44,6 +44,12 @@ def get_repository(namespace_name, repository_name):
 
 
 def purge_repository(namespace_name, repository_name):
+  """ Completely delete all traces of the repository. Will return True upon
+      complete success, and False upon partial or total failure. Garbage
+      collection is incremental and repeatable, so this return value does
+      not need to be checked or responded to.
+      """
+
   repo = _basequery.get_existing_repository(namespace_name, repository_name)
 
   # Delete all tags to allow gc to reclaim storage
@@ -57,12 +63,18 @@ def purge_repository(namespace_name, repository_name):
   unreferenced_candidates = set(img[0] for img in unreferenced_image_q.tuples())
 
   # Gc to remove the images and storage
-  garbage_collect_repo(repo, previously_referenced | unreferenced_candidates)
+  all_repo_images = previously_referenced | unreferenced_candidates
+  successful_gc = garbage_collect_repo(repo, all_repo_images)
+
+  if not successful_gc:
+    return False
 
   # Delete the rest of the repository metadata
   fetched = _basequery.get_existing_repository(namespace_name, repository_name)
   fetched.delete_instance(recursive=True, delete_nullable=False)
 
+  return True
+
 
 @ttl_cache(maxsize=1, ttl=600)
 def _get_gc_expiration_policies():
@@ -112,6 +124,13 @@ def find_repository_with_garbage(limit_to_gc_policy_s):
 
 
 def garbage_collect_repo(repo, extra_candidate_set=None):
+  """ Garbage collect the specified repository object. This will remove all
+      images, derived images, and other associated metadata, for images which
+      are no longer referenced by a tag or another image which is itself
+      tagged. Returns True if garbage collection was completed without error
+      and False otherwise. Retries are safe and work incrementally, so this
+      return value does not need to be checked or handled.
+      """
   logger.debug('Garbage collecting repository %s', repo.id)
 
   storage_id_whitelist = set()
@@ -122,7 +141,7 @@ def garbage_collect_repo(repo, extra_candidate_set=None):
 
   if not len(candidate_orphan_image_set):
     logger.debug('No candidate images for GC for repo: %s', repo.id)
-    return
+    return True
 
   candidates_orphans = list(candidate_orphan_image_set)
 
@@ -190,18 +209,20 @@ def garbage_collect_repo(repo, extra_candidate_set=None):
            .execute())
         except IntegrityError:
           logger.info('Could not GC derived images %s; will try again soon', to_remove)
-          return
+          return False
 
       try:
         Image.delete().where(Image.id << to_remove).execute()
       except IntegrityError:
         logger.info('Could not GC images %s; will try again soon', to_remove)
-        return
+        return False
 
   if len(to_remove) > 0:
     logger.info('Garbage collecting storage for images: %s', to_remove)
     storage.garbage_collect_storage(storage_id_whitelist)
 
+  return True
+
 
 def star_repository(user, repository):
   """ Stars a repository. """