#18458: Method session.get_expiry_age() does not return what the doc says
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Reporter: | Owner: nobody
martin.bouladour@… | Status: new
Type: Bug | Version: 1.4
Component: | Keywords: session expiration expiry age
contrib.sessions | get_expiry_age
Severity: Normal | Has patch: 0
Triage Stage: | UI/UX: 0
Unreviewed |
Easy pickings: 0 |
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This is either a bug in the doc or in the code.
The doc for the !SessionBase.get_expiry_age() method [1] says:
''get_expiry_age()[[BR]]Returns the number of seconds until this session
expires. For sessions with no custom expiration (or those set to expire at
browser close), this will equal SESSION_COOKIE_AGE.''
This means that it should return the session's remaining time to live when
expiration has been customized using one of these:[[BR]]
A) {{{set_expiry(seconds) # integer != 0}}}[[BR]]
B) {{{set_expiry(datetime)}}}[[BR]]
C) {{{set_expiry(timedelta)}}}
It works as documented in the cases B and C. But when set_expiry() has
been used with seconds (A), then get_expiry_age() does the unexpected
thing of returning the exact value that has been passed to set_expiry().
In other words, when you give 300 to set_expiry(), get_expiry_age() will
always return 300. That is not “the number of seconds until this session
expires”.
Looking at the code [2], it is obvious that a difference is calculated
only when the expiry value is a datetime:
{{{
def get_expiry_age(self):
"""Get the number of seconds until the session expires."""
expiry = self.get('_session_expiry')
if not expiry: # Checks both None and 0 cases
return settings.SESSION_COOKIE_AGE
if not isinstance(expiry, datetime):
return expiry
delta = expiry - timezone.now()
return delta.days * 86400 + delta.seconds
}}}
I'm not sure about the purpose of this method and I don't know the design
decisions that led to it, but I assume that if you don't want this
function to use the session's last-modified datetime, then you may just
need to edit the documentation to clarify this point (and maybe the
docstring).
On the other hand, in my humble opinion, I think that this method’s
behavior is quite surprising (even if it were working as documented)
because the value it returns really depends on how the expiration has been
defined. I believe it would be nice to make it return the number of
seconds until the session expires for ''any'' active session, with no
exceptional cases. And while we're at it, maybe also rename it to
something that reflect better what it does, for instance
"get_remaining_time_to_live" or "get_time_left". (Then again, maybe I
didn't understand the purpose of this method.)
I hope this is helping.
Anyway, thank you all for this great framework!
Martin Bouladour
[1]
https://docs.djangoproject.com/en/1.4/topics/http/sessions/#django.contrib.sessions.backends.base.SessionBase.get_expiry_age
[2]
https://github.com/django/django/blob/1.4/django/contrib/sessions/backends/base.py#L170
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Ticket URL: <https://code.djangoproject.com/ticket/18458>
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