在使用 Pyramid 框架和 Jinja2 模板引擎与新的 Python 2.7 运行时（线程安全模式）和 GAE 1.6.0 预发布 SDK 一起运行时出现了一个问题。我们按照官方文档对应用程序进行了修改，包括在 app.yaml 中设置 runtime: python27、threadsafe: true，并删除了 main() 函数。当自生成响应时，应用程序运行正常。但是，当我们尝试使用 Jinja2 时，出现了以下异常：
ERROR 2011-11-07 00:10:34,356 wsgi.py:170]
Traceback (most recent call last):
File "/gae/google/appengine/runtime/wsgi.py", line 168, in Handle
[...]
File "/myapp/source/myapp-tip/main.py", line 29, in <module>
config.include('pyramid_jinja2')
File "/myapp/source/myapp-tip/lib/dist/pyramid/config/__init__.py", line 616, in include
c(configurator)
File "lib/dist/pyramid_jinja2/__init__.py", line 390, in includeme
_get_or_build_default_environment(config.registry)
File "/lib/dist/pyramid_jinja2/__init__.py", line 217, in _get_or_build_default_environment
_setup_environment(registry)
File "/lib/dist/pyramid_jinja2/__init__.py", line 253, in _setup_environment
package = _caller_package(('pyramid_jinja2', 'jinja2', 'pyramid.config'))
File "/lib/dist/pyramid_jinja2/__init__.py", line 136, in caller_package
for t in self.inspect.stack():
File "/usr/lib/python2.7/inspect.py", line 1056, in stack
return getouterframes(sys._getframe(1), context)
File "/usr/lib/python2.7/inspect.py", line 1034, in getouterframes
framelist.append((frame,) + getframeinfo(frame, context))
File "/usr/lib/python2.7/inspect.py", line 1009, in getframeinfo
lines, lnum = findsource(frame)
File "/usr/lib/python2.7/inspect.py", line 534, in findsource
module = getmodule(object, file)
File "/usr/lib/python2.7/inspect.py", line 506, in getmodule
main = sys.modules['__main__']
KeyError: '__main__'
我们尝试通过修改 pyramid_jinja2 代码来解决这个问题，但又遇到了另一个异常：
ERROR 2011-11-04 12:06:38,720 wsgi.py:170]
Traceback (most recent call last):
File "/gae/google/appengine/runtime/wsgi.py", line 168, in Handle
handler = _config_handle.add_wsgi_middleware(self._LoadHandler())
[...]
File "/myapp/source/myapp-tip/main.py", line 29, in <module>
config.add_jinja2_search_path("templates")
File "/myapp/source/myapp-tip/lib/dist/pyramid/config/util.py", line 28, in wrapper
result = wrapped(self, *arg, **kw)
File "/lib/dist/pyramid_jinja2/__init__.py", line 311, in add_jinja2_search_path
env.loader.searchpath.append(abspath_from_resource_spec(d))
File "/myapp/source/myapp-tip/lib/dist/pyramid/asset.py", line 38, in abspath_from_asset_spec
return pkg_resources.resource_filename(pname, filename)
File "/myapp/source/myapp-tip/pkg_resources.py", line 840, in resource_filename
return get_provider(package_or_requirement).get_resource_filename(
File "/myapp/source/myapp-tip/pkg_resources.py", line 160, in get_provider
__import__(moduleOrReq)
File "/gae/google/appengine/tools/dev_appserver_import_hook.py", line 640, in Decorate
return func(self, *args, **kwargs)
File "/gae/google/appengine/tools/dev_appserver_import_hook.py", line 1756, in load_module
return self.FindAndLoadModule(submodule, fullname, search_path)
File "/gae/google/appengine/tools/dev_appserver_import_hook.py", line 640, in Decorate
return func(self, *args, **kwargs)
File "/gae/google/appengine/tools/dev_appserver_import_hook.py", line 1628, in FindAndLoadModule
description)
File "/gae/google/appengine/tools/dev_appserver_import_hook.py", line 640, in Decorate
return func(self, *args, **kwargs)
File "/gae/google/appengine/tools/dev_appserver_import_hook.py", line 1571, in LoadModuleRestricted
description)
ImportError: Cannot re-init internal module __main__
我们在排查问题时发现 Pyramid 框架试图在幕后做一些事情。从第二个异常的堆栈跟踪中，我们可以看到它似乎正在尝试解析一个资源，但我们不确定为什么它要重新加载 main 模块。我们甚至不确定我们的问题是由 Pyramid 框架还是 GAE 引起的。
解决方案
幸运的是，我们能够找到一种解决方法，使用 Pyramid 1.3 的 AssetResolver 成功解决了这个问题。代码修改如下：
from pyramid.config import Configurator
from pyramid.renderers import render_to_response
def main(request):
"""
Main request handler.
"""
# Initialize the Pyramid configuration.
config = Configurator()
# Configure Jinja2 templating.
config.include('pyramid_jinja2')
# Allow static asset access.
resolver = AssetResolver()
resolver.add_static('myapp', 'myapp:static')
config.add_jinja2_search_path("templates")
# Define a route for the main page.
config.add_route('home', '/')
# Define the view for the main page.
@config.route_view('home', renderer='index.html')
def home(request):
"""
Main page view.
"""
return {'project': 'MyProject'}
# Create the Pyramid application.
app = config.make_wsgi_app()
# Process the request and return the response.
return app(request)
解决了 main 重新加载的问题后，我们又遇到了另一个问题：AssetResolver 的生命周期和作用域是什么？我们仍在探索这个问题，但我们相信我们会找到解决方案。
