Merge pull request #772 from docker/710_lockout_db_setup

Lock out setup_database method

Author: dmp42

docker_registry/lib/index/db.py

@@ -4,6 +4,7 @@
 """
 
 from ... import storage
+from ... import toolkit
 from .. import config
 from . import Index
 import sqlalchemy
@@ -61,6 +62,7 @@ def __init__(self, database=None):
         self._setup_database()
         super(SQLAlchemyIndex, self).__init__()
 
+    @toolkit.exclusive_lock
     def _setup_database(self):
         session = self._session()
         if self._engine.has_table(table_name=Version.__tablename__):

docker_registry/toolkit.py

@@ -4,6 +4,7 @@
 import distutils.version
 import functools
 import logging
+import os
 import random
 import re
 import string
@@ -278,6 +279,22 @@ def wrapper(repository, *args, **kwargs):
     return wrapper
 
 
+def exclusive_lock(f):
+    @functools.wraps(f)
+    def wrapper(*args, **kwargs):
+        lock_path = os.path.join(
+            '/var/lock', 'registry.{0}.lock'.format(f.func_name)
+        )
+        if os.path.exists(lock_path):
+            return
+        lock_file = open(lock_path, 'w')
+        lock_file.close()
+        result = f(*args, **kwargs)
+        os.remove(lock_path)
+        return result
+    return wrapper
+
+
 def get_repository():
     auth = flask.request.headers.get('authorization', '')
     if not auth: