mirror of
https://gitlab.crans.org/bde/nk20
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60 lines
1.9 KiB
Python
60 lines
1.9 KiB
Python
# Copyright (C) 2018-2020 by BDE ENS Paris-Saclay
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# SPDX-License-Identifier: GPL-3.0-or-later
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from functools import lru_cache
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from time import time
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from django.contrib.sessions.models import Session
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from note_kfet.middlewares import get_current_session
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def memoize(f):
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"""
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Memoize results and store in sessions
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This decorator is useful for permissions: they are loaded once needed, then stored for next calls.
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The storage is contained with sessions since it depends on the selected mask.
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"""
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sess_funs = {}
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last_collect = time()
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def collect():
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"""
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Clear cache of results when sessions are invalid, to flush useless data.
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This function is called every minute.
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"""
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nonlocal sess_funs
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new_sess_funs = {}
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for sess_key in sess_funs:
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if Session.objects.filter(session_key=sess_key).exists():
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new_sess_funs[sess_key] = sess_funs[sess_key]
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sess_funs = new_sess_funs
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def func(*args, **kwargs):
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nonlocal last_collect
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if time() - last_collect > 60:
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# Clear cache
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collect()
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last_collect = time()
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# If there is no session, then we don't memoize anything.
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sess = get_current_session()
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if sess is None or sess.session_key is None:
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return f(*args, **kwargs)
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sess_key = sess.session_key
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if sess_key not in sess_funs:
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# lru_cache makes the job of memoization
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# We store only the 512 latest data per session. It has to be enough.
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sess_funs[sess_key] = lru_cache(512)(f)
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try:
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return sess_funs[sess_key](*args, **kwargs)
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except TypeError: # For add permissions, objects are not hashable (not yet created). Don't memoize this case.
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return f(*args, **kwargs)
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func.func_name = f.__name__
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return func
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