cherrypy.lib.sessions module¶
Session implementation for CherryPy.
You need to edit your config file to use sessions. Here’s an example:
[/]
tools.sessions.on = True
tools.sessions.storage_class = cherrypy.lib.sessions.FileSession
tools.sessions.storage_path = "/home/site/sessions"
tools.sessions.timeout = 60
This sets the session to be stored in files in the directory
/home/site/sessions, and the session timeout to 60 minutes. If you omit
storage_class
, the sessions will be saved in RAM.
tools.sessions.on
is the only required line for working sessions,
the rest are optional.
By default, the session ID is passed in a cookie, so the client’s browser must have cookies enabled for your site.
To set data for the current session, use
cherrypy.session['fieldname'] = 'fieldvalue'
;
to get data use cherrypy.session.get('fieldname')
.
Locking sessions¶
By default, the 'locking'
mode of sessions is 'implicit'
, which means
the session is locked early and unlocked late. Be mindful of this default mode
for any requests that take a long time to process (streaming responses,
expensive calculations, database lookups, API calls, etc), as other concurrent
requests that also utilize sessions will hang until the session is unlocked.
If you want to control when the session data is locked and unlocked,
set tools.sessions.locking = 'explicit'
. Then call
cherrypy.session.acquire_lock()
and cherrypy.session.release_lock()
.
Regardless of which mode you use, the session is guaranteed to be unlocked when
the request is complete.
Expiring Sessions¶
You can force a session to expire with cherrypy.lib.sessions.expire()
.
Simply call that function at the point you want the session to expire, and it
will cause the session cookie to expire client-side.
Session Fixation Protection¶
If CherryPy receives, via a request cookie, a session id that it does not recognize, it will reject that id and create a new one to return in the response cookie. This helps prevent session fixation attacks. However, CherryPy “recognizes” a session id by looking up the saved session data for that id. Therefore, if you never save any session data, you will get a new session id for every request.
A side effect of CherryPy overwriting unrecognised session ids is that if you
have multiple, separate CherryPy applications running on a single domain (e.g.
on different ports), each app will overwrite the other’s session id because by
default they use the same cookie name ("session_id"
) but do not recognise
each others sessions. It is therefore a good idea to use a different name for
each, for example:
[/]
...
tools.sessions.name = "my_app_session_id"
Expiration Dates¶
The response cookie will possess an expiration date to inform the client at which point to stop sending the cookie back in requests. If the server time and client time differ, expect sessions to be unreliable. Make sure the system time of your server is accurate.
CherryPy defaults to a 60-minute session timeout, which also applies to the cookie which is sent to the client. Unfortunately, some versions of Safari (“4 public beta” on Windows XP at least) appear to have a bug in their parsing of the GMT expiration date–they appear to interpret the date as one hour in the past. Sixty minutes minus one hour is pretty close to zero, so you may experience this bug as a new session id for every request, unless the requests are less than one second apart. To fix, try increasing the session.timeout.
On the other extreme, some users report Firefox sending cookies after their expiration date, although this was on a system with an inaccurate system time. Maybe FF doesn’t trust system time.
- class cherrypy.lib.sessions.FileSession(id=None, **kwargs)[source]¶
Bases:
Session
Implementation of the File backend for sessions
- storage_path
The folder where session data will be saved. Each session will be saved as pickle.dump(data, expiration_time) in its own file; the filename will be self.SESSION_PREFIX + self.id.
- lock_timeout
A timedelta or numeric seconds indicating how long to block acquiring a lock. If None (default), acquiring a lock will block indefinitely.
- LOCK_SUFFIX = '.lock'¶
- SESSION_PREFIX = 'session-'¶
- pickle_protocol = 4¶
- class cherrypy.lib.sessions.MemcachedSession(id=None, **kwargs)[source]¶
Bases:
Session
- locks = {}¶
- mc_lock = <unlocked _thread.RLock object owner=0 count=0>¶
- servers = ['localhost:11211']¶
- class cherrypy.lib.sessions.RamSession(id=None, **kwargs)[source]¶
Bases:
Session
- cache = {}¶
- locks = {}¶
- class cherrypy.lib.sessions.Session(id=None, **kwargs)[source]¶
Bases:
object
A CherryPy dict-like Session object (one per request).
- _id = None¶
- clean_freq = 5¶
The poll rate for expired session cleanup in minutes.
- clean_thread = None¶
Class-level Monitor which calls self.clean_up.
- debug = False¶
If True, log debug information.
- property id¶
Return the current session id.
- id_observers = None¶
A list of callbacks to which to pass new id’s.
- loaded = False¶
If True, data has been retrieved from storage.
This should happen automatically on the first attempt to access session data.
- locked = False¶
If True, this session instance has exclusive read/write access to session data.
- missing = False¶
True if the session requested by the client did not exist.
- now()[source]¶
Generate the session specific concept of ‘now’.
Other session providers can override this to use alternative, possibly timezone aware, versions of ‘now’.
- originalid = None¶
The session id passed by the client. May be missing or unsafe.
- pop(key, default=False)[source]¶
Remove the specified key and return the corresponding value.
If key is not found, default is returned if given, otherwise KeyError is raised.
- regenerated = False¶
True if the application called session.regenerate().
This is not set by internal calls to regenerate the session id.
- timeout = 60¶
Number of minutes after which to delete session data.
- cherrypy.lib.sessions._add_MSIE_max_age_workaround(cookie, timeout)[source]¶
We’d like to use the “max-age” param as indicated in http://www.faqs.org/rfcs/rfc2109.html but IE doesn’t save it to disk and the session is lost if people close the browser. So we have to use the old “expires” … sigh …
- cherrypy.lib.sessions.init(storage_type=None, path=None, path_header=None, name='session_id', timeout=60, domain=None, secure=False, clean_freq=5, persistent=True, httponly=False, debug=False, **kwargs)[source]¶
Initialize session object (using cookies).
- storage_class
The Session subclass to use. Defaults to RamSession.
- storage_type
(deprecated) One of ‘ram’, ‘file’, memcached’. This will be used to look up the corresponding class in cherrypy.lib.sessions globals. For example, ‘file’ will use the FileSession class.
- path
The ‘path’ value to stick in the response cookie metadata.
- path_header
If ‘path’ is None (the default), then the response cookie ‘path’ will be pulled from request.headers[path_header].
- name
The name of the cookie.
- timeout
The expiration timeout (in minutes) for the stored session data. If ‘persistent’ is True (the default), this is also the timeout for the cookie.
- domain
The cookie domain.
- secure
If False (the default) the cookie ‘secure’ value will not be set. If True, the cookie ‘secure’ value will be set (to 1).
- clean_freq (minutes)
The poll rate for expired session cleanup.
- persistent
If True (the default), the ‘timeout’ argument will be used to expire the cookie. If False, the cookie will not have an expiry, and the cookie will be a “session cookie” which expires when the browser is closed.
- httponly
If False (the default) the cookie ‘httponly’ value will not be set. If True, the cookie ‘httponly’ value will be set (to 1).
Any additional kwargs will be bound to the new Session instance, and may be specific to the storage type. See the subclass of Session you’re using for more information.
- cherrypy.lib.sessions.set_response_cookie(path=None, path_header=None, name='session_id', timeout=60, domain=None, secure=False, httponly=False)[source]¶
Set a response cookie for the client.
- path
the ‘path’ value to stick in the response cookie metadata.
- path_header
if ‘path’ is None (the default), then the response cookie ‘path’ will be pulled from request.headers[path_header].
- name
the name of the cookie.
- timeout
the expiration timeout for the cookie. If 0 or other boolean False, no ‘expires’ param will be set, and the cookie will be a “session cookie” which expires when the browser is closed.
- domain
the cookie domain.
- secure
if False (the default) the cookie ‘secure’ value will not be set. If True, the cookie ‘secure’ value will be set (to 1).
- httponly
If False (the default) the cookie ‘httponly’ value will not be set. If True, the cookie ‘httponly’ value will be set (to 1).