From 6c4e78ec0c2de8528bf47ac587436f27512a931e Mon Sep 17 00:00:00 2001
From: Jake Moshenko <jake.moshenko@coreos.com>
Date: Wed, 25 Feb 2015 17:49:46 -0500
Subject: [PATCH] Fix the deadlock in tags.

---
 data/model/legacy.py | 38 ++++++++++++++++----------------------
 1 file changed, 16 insertions(+), 22 deletions(-)

diff --git a/data/model/legacy.py b/data/model/legacy.py
index 85b533053..5188a9710 100644
--- a/data/model/legacy.py
+++ b/data/model/legacy.py
@@ -1580,25 +1580,16 @@ def list_repository_tags(namespace_name, repository_name, include_hidden=False):
 
 
 def _garbage_collect_tags(namespace_name, repository_name):
-    inner = (RepositoryTag
-             .select(RepositoryTag.id,
-                     RepositoryTag.lifetime_end_ts,
-                     RepositoryTag.repository)
-             .alias('rt'))
-    to_delete = (RepositoryTag
-                 .select(inner.c.id)
-                 .from_(inner)
-                 .join(Repository, on=(inner.c.repository_id == Repository.id))
-                 .join(Namespace, on=(Repository.namespace_user == Namespace.id))
-                 .where(Repository.name == repository_name, Namespace.username == namespace_name,
-                        ~(inner.c.lifetime_end_ts >> None),
-                        (inner.c.lifetime_end_ts + Namespace.removed_tag_expiration_s) <=
-                         int(time.time())))
+  # We do this without using a join to prevent holding read locks on the repository table
+  repo = _get_repository(namespace_name, repository_name)
+  now = int(time.time())
 
-    (RepositoryTag
-     .delete()
-     .where(RepositoryTag.id << to_delete)
-     .execute())
+  (RepositoryTag
+   .delete()
+   .where(RepositoryTag.repository == repo,
+          ~(RepositoryTag.lifetime_end_ts >> None),
+          (RepositoryTag.lifetime_end_ts + repo.namespace_user.removed_tag_expiration_s) <= now)
+   .execute())
 
 
 def garbage_collect_repository(namespace_name, repository_name):
@@ -1798,20 +1789,23 @@ def create_or_update_tag(namespace_name, repository_name, tag_name,
 
     now_ts = int(time.time())
 
+    created = RepositoryTag.create(repository=repo, image=image, name=tag_name,
+                                   lifetime_start_ts=now_ts)
+
     try:
       # When we move a tag, we really end the timeline of the old one and create a new one
       query = _tag_alive(RepositoryTag
                          .select()
-                         .where(RepositoryTag.repository == repo, RepositoryTag.name == tag_name))
-      tag = db_for_update(query).get()
+                         .where(RepositoryTag.repository == repo, RepositoryTag.name == tag_name,
+                                RepositoryTag.id != created.id))
+      tag = query.get()
       tag.lifetime_end_ts = now_ts
       tag.save()
     except RepositoryTag.DoesNotExist:
       # No tag that needs to be ended
       pass
 
-    return RepositoryTag.create(repository=repo, image=image, name=tag_name,
-                                lifetime_start_ts=now_ts)
+    return created
 
 
 def delete_tag(namespace_name, repository_name, tag_name):