I am using apache2, python26, pretty much latest version of beaker, mod_wsgi

Here's my code, I acquired this from http://beaker.groovie.org/sessions.html#using

from beaker.middleware import SessionMiddleware

def simple_app(environ, start_response):
    # Get the session object from the environ
    session = environ['beaker.session']

    # Check to see if a value is in the session
    if 'logged_in' in session:
        user = True
    else:
        user = False

    # Set some other session variable
    session['user_id'] = 10

    start_response('200 OK', [('Content-type', 'text/plain')])
    return ['User is logged in: %s' % user]

# Configure the SessionMiddleware
session_opts = {
    'session.type': 'file',
    'session.cookie_expires': True,
}
wsgi_app = SessionMiddleware(simple_app, session_opts)

This works fine after i visit localhost/beaker2.wsgi. After I try two changes the website fails:

1. add

session.save()

or

2. change

'session.type': 'cookie',

So why do I recieve errors after i add session.save() or change session.type to cookie?

full trackback: sorry for that dates and everything, made it happen with tail -f

To the session.save() error:

[Sun May 01 04:35:55 2011] [error] [client 127.0.0.1] mod_wsgi (pid=25311): Exception occurred processing WSGI script '/home/yizi/apache2/www/beaker2.wsgi'.
[Sun May 01 04:35:55 2011] [error] [client 127.0.0.1] Traceback (most recent call last):
[Sun May 01 04:35:55 2011] [error] [client 127.0.0.1]   File "/usr/local/lib/python2.6/dist-packages/Beaker-1.5.4-py2.6.egg/beaker/middleware.py", line 152, in __call__
[Sun May 01 04:35:55 2011] [error] [client 127.0.0.1]     return self.wrap_app(environ, session_start_response)
[Sun May 01 04:35:55 2011] [error] [client 127.0.0.1]   File "/home/yizi/apache2/www/beaker2.wsgi", line 21, in simple_app
[Sun May 01 04:35:55 2011] [error] [client 127.0.0.1]     start_response('200 OK', [('Content-type', 'text/html')])
[Sun May 01 04:35:55 2011] [error] [client 127.0.0.1]   File "/usr/local/lib/python2.6/dist-packages/Beaker-1.5.4-py2.6.egg/beaker/middleware.py", line 146, in session_start_response
[Sun May 01 04:35:55 2011] [error] [client 127.0.0.1]     session.persist()
[Sun May 01 04:35:55 2011] [error] [client 127.0.0.1]   File "/usr/local/lib/python2.6/dist-packages/Beaker-1.5.4-py2.6.egg/beaker/session.py", line 609, in persist
[Sun May 01 04:35:55 2011] [error] [client 127.0.0.1]     self._session().save()
[Sun May 01 04:35:55 2011] [error] [client 127.0.0.1]   File "/usr/local/lib/python2.6/dist-packages/Beaker-1.5.4-py2.6.egg/beaker/session.py", line 275, in save
[Sun May 01 04:35:55 2011] [error] [client 127.0.0.1]     **self.namespace_args)
[Sun May 01 04:35:55 2011] [error] [client 127.0.0.1]   File "/usr/local/lib/python2.6/dist-packages/Beaker-1.5.4-py2.6.egg/beaker/container.py", line 518, in __init__
[Sun May 01 04:35:55 2011] [error] [client 127.0.0.1]     raise MissingCacheParameter("data_dir or file_dir is required")
[Sun May 01 04:35:55 2011] [error] [client 127.0.0.1] MissingCacheParameter: data_dir or file_dir is required

This is actually the cookie error:

[Sun May 01 04:53:18 2011] [error] [client 127.0.0.1] mod_wsgi (pid=25312): Exception occurred processing WSGI script '/home/yizi/apache2/www/beaker2.wsgi'.
[Sun May 01 04:53:18 2011] [error] [client 127.0.0.1] Traceback (most recent call last):
[Sun May 01 04:53:18 2011] [error] [client 127.0.0.1]   File "/usr/local/lib/python2.6/dist-packages/Beaker-1.5.4-py2.6.egg/beaker/middleware.py", line 152, in __call__
[Sun May 01 04:53:18 2011] [error] [client 127.0.0.1]     return self.wrap_app(environ, session_start_response)
[Sun May 01 04:53:18 2011] [error] [client 127.0.0.1]   File "/home/yizi/apache2/www/beaker2.wsgi", line 10, in simple_app
[Sun May 01 04:53:18 2011] [error] [client 127.0.0.1]     if 'logged_in' in session:
[Sun May 01 04:53:18 2011] [error] [client 127.0.0.1]   File "/usr/local/lib/python2.6/dist-packages/Beaker-1.5.4-py2.6.egg/beaker/session.py", line 579, in __contains__
[Sun May 01 04:53:18 2011] [error] [client 127.0.0.1]     return self._session().has_key(key)
[Sun May 01 04:53:18 2011] [error] [client 127.0.0.1]   File "/usr/local/lib/python2.6/dist-packages/Beaker-1.5.4-py2.6.egg/beaker/session.py", line 547, in _session
[Sun May 01 04:53:18 2011] [error] [client 127.0.0.1]     self.__dict__['_sess'] = CookieSession(req, **params)
[Sun May 01 04:53:18 2011] [error] [client 127.0.0.1]   File "/usr/local/lib/python2.6/dist-packages/Beaker-1.5.4-py2.6.egg/beaker/session.py", line 373, in __init__
[Sun May 01 04:53:18 2011] [error] [client 127.0.0.1]     raise BeakerException("No validate_key specified for Cookie only "
[Sun May 01 04:53:18 2011] [error] [client 127.0.0.1] BeakerException: No validate_key specified for Cookie only Session.