Enable caching of blobs in V2 registry protocol, to avoid DB connections after the cache has been loaded

This should help for bursty pull traffic, as it will avoid DB connections on a huge % of requests

app.py

@@ -23,6 +23,7 @@ from data import model
 from data.archivedlogs import LogArchive
 from data.billing import Billing
 from data.buildlogs import BuildLogs
+from data.cache import InMemoryDataModelCache
 from data.model.user import LoginWrappedDBUser
 from data.queue import WorkQueue, BuildMetricQueueReporter
 from data.userevent import UserEventsBuilderModule
@@ -160,16 +161,7 @@ def _request_end(resp):
   if request.user_agent is not None:
     extra["user-agent"] = request.user_agent.string
 
-  user = get_authenticated_user()
-
-  if user:
-    extra['user'] = {'email': user.email,
-                     'uuid': user.uuid,
-                     'org': user.organization,
-                     'robot': user.robot}
-
   logger.info("request-end", extra=extra)
-
   logger.debug('Ending request: %s', request.path)
   return resp
 
@@ -188,6 +180,8 @@ Principal(app, use_sessions=False)
 
 tf = app.config['DB_TRANSACTION_FACTORY']
 
+# TODO(jschorr): make this configurable
+model_cache = InMemoryDataModelCache()
 
 avatar = Avatar(app)
 login_manager = LoginManager(app)