ScoDoc/app/scodoc/sco_cache.py

# -*- mode: python -*-
# -*- coding: utf-8 -*-

##############################################################################
#
# Gestion scolarite IUT
#
# Copyright (c) 1999 - 2021 Emmanuel Viennet.  All rights reserved.
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
#
#   Emmanuel Viennet      emmanuel.viennet@viennet.net
#
##############################################################################

"""Gestion des caches

  Ré-écrite pour ScoDoc8, utilise flask_caching et memcached

  ScoDoc est maintenant multiprocessus / mono-thread, avec un cache en mémoire partagé.
"""


# API ScoDoc8 pour les caches:
#  sco_core.get_notes_cache(context).get_NotesTable(context, formsemestre_id)
#   => sco_cache.NotesTableCache.get(formsemestre_id)
#
#  sco_core.inval_cache(context, formsemestre_id=None, pdfonly=False, formsemestre_id_list=None)
#   => deprecated, sco_cache.inval_cache(formsemestre_id=None, pdfonly=False, formsemestre_id_list=None)
#
#
# Nouvelles fonctions:
#  sco_cache.NotesTableCache.delete(formsemestre_id)
#  sco_cache.NotesTableCache.delete_many(formsemestre_id_list)
#
# Bulletins PDF:
#  sco_cache.PDFBulCache.get(formsemestre_id, version)
#  sco_cache.PDFBulCache.set(formsemestre_id, version, filename, pdfdoc)
#  sco_cache.PDFBulCache.delete(formsemestre_id) suppr. toutes les versions

# Evaluations:
#  sco_cache.EvaluationCache.get(evaluation_id), set(evaluation_id, value), delete(evaluation_id),
#

from collections import defaultdict

from flask import g
from flask_caching import Cache

from app.scodoc.notes_log import log

CACHE = Cache(config={"CACHE_TYPE": "MemcachedCache"})  # XXX TODO: configuration file


class ScoDocCache:
    """Cache for ScoDoc objects.
    keys are prefixed by the current departement.
    """

    prefix = ""

    @classmethod
    def _get_key(cls, oid):
        return cls.prefix + g.scodoc_dept + oid

    @classmethod
    def get(cls, oid):
        """Returns cached evaluation, or None"""
        return CACHE.get(cls._get_key(oid))

    @classmethod
    def set(cls, oid, value):
        """Store evaluation"""
        return CACHE.set(cls._get_key(oid), value)

    @classmethod
    def delete(cls, oid):
        """Remove from cache"""
        CACHE.delete(cls._get_key(oid))

    @classmethod
    def delete_many(cls, oids):
        """Remove multiple keys at once"""
        CACHE.delete_many(oids)


class EvaluationCache(ScoDocCache):
    "Cache for evaluations"
    prefix = "EVAL"


class NotesTableCache(ScoDocCache):
    prefix = "NT"
    listeners = defaultdict(list)  # oid : list of callback functions

    @classmethod
    def add_listener(cls, func, oid):
        """Add a function which will be called each time and object is modified:
        the function will be called as func(oid)
        """
        cls.listeners[oid].append(func)

    @classmethod
    def delete(cls, oid):
        for listener in cls.listeners[oid]:
            listener(oid)
        super().delete(oid)

    @classmethod
    def delete_many(cls, oids):
        for oid in oids:
            for listener in cls.listeners[oid]:
                listener(oid)
        super().delete_many(oids)


# XXX OBSOLETE A ENLEVER XXX
class simpleCache:
    """A simple cache wich cache data for a most "duration" seconds."""

    def __init__(self):
        self.cache = {}
        self.inval_cache()  # >

    def inval_cache(self, key=None):  # >
        if key:
            if key in self.cache:
                del self.cache[key]
        else:
            # clear all entries
            self.cache = {}  # key : data

    def set(self, key, data):
        self.cache[key] = data

    def get(self, key):
        """returns None if not in cache"""
        return self.cache.get(key, None)


class expiringCache(simpleCache):
    """A simple cache wich cache data for a most "duration" seconds.

    This is used for users (which may be updated from external
    information systems)
    """

    def __init__(self, max_validity=60):
        simpleCache.__init__(self)
        self.max_validity = max_validity

    def set(self, key, data):
        simpleCache.set(self, key, (data, time.time()))

    def get(self, key):
        info = simpleCache.get(self, key)
        if info:
            data, t = info
            if time.time() - t < self.max_validity:
                return data
            else:
                # expired
                self.inval_cache(key)  # >
                return None
        else:
            return None  # not in cache