From 75aa412d1dadda6c955e094e91380c7ae70695fb Mon Sep 17 00:00:00 2001 From: Chris McDonough Date: Tue, 7 Sep 2010 20:48:54 +0000 Subject: - Prevent a race condition which could result in a ``RuntimeError`` when rendering a Chameleon template that has not already been rendered once. This would usually occur directly after a restart, when more than one person or thread is trying to execute the same view at the same time: https://bugs.launchpad.net/karl3/+bug/621364 --- CHANGES.txt | 6 ++++++ repoze/bfg/renderers.py | 21 ++++++++++++++++++--- 2 files changed, 24 insertions(+), 3 deletions(-) diff --git a/CHANGES.txt b/CHANGES.txt index ccc766637..4e2e54dcf 100644 --- a/CHANGES.txt +++ b/CHANGES.txt @@ -12,6 +12,12 @@ Bug Fixes - Fix another bug in ``repoze.bfg.static_url`` URL generation: too many slashes in generated URL. +- Prevent a race condition which could result in a ``RuntimeError`` + when rendering a Chameleon template that has not already been + rendered once. This would usually occur directly after a restart, + when more than one person or thread is trying to execute the same + view at the same time: https://bugs.launchpad.net/karl3/+bug/621364 + Internal -------- diff --git a/repoze/bfg/renderers.py b/repoze/bfg/renderers.py index 13e578d36..e4e19013c 100644 --- a/repoze/bfg/renderers.py +++ b/repoze/bfg/renderers.py @@ -1,5 +1,6 @@ import os import pkg_resources +import threading from webob import Response @@ -150,7 +151,12 @@ def string_renderer_factory(name): # utility functions, not API -def template_renderer_factory(spec, impl): +# Lock to prevent simultaneous registry writes; used in +# template_renderer_factory. template_renderer_factory may be called +# at runtime, from more than a single thread. +registry_lock = threading.Lock() + +def template_renderer_factory(spec, impl, lock=registry_lock): reg = get_current_registry() if os.path.isabs(spec): # 'spec' is an absolute filename @@ -159,7 +165,12 @@ def template_renderer_factory(spec, impl): renderer = reg.queryUtility(ITemplateRenderer, name=spec) if renderer is None: renderer = impl(spec) - reg.registerUtility(renderer, ITemplateRenderer, name=spec) + # cache the template + try: + lock.acquire() + reg.registerUtility(renderer, ITemplateRenderer, name=spec) + finally: + lock.release() else: # spec is a package:relpath resource spec renderer = reg.queryUtility(ITemplateRenderer, name=spec) @@ -178,7 +189,11 @@ def template_renderer_factory(spec, impl): renderer = impl(abspath) if not _reload_resources(): # cache the template - reg.registerUtility(renderer, ITemplateRenderer, name=spec) + try: + lock.acquire() + reg.registerUtility(renderer, ITemplateRenderer, name=spec) + finally: + lock.release() return renderer -- cgit v1.2.3