app/django/core/cache/backends/locmem.py
author Lennard de Rijk <ljvderijk@gmail.com>
Thu, 05 Feb 2009 22:15:38 +0000
changeset 1225 1d5c58e24fd3
parent 323 ff1a9aa48cfd
permissions -rw-r--r--
Org applications can now only be made by a user when a program allows it. To do this a new access_type has been added called apply. This ensures that users can only used the seeded version of create. Also the review_overview now has his own access type to ensure the separability of hosts for different sponsors in case of org app reviews. Note that the access checks for hosts are broken and only give access to developers at the moment. Patch by: Lennard de Rijk Reviewed by: to-be-reviewed

"Thread-safe in-memory cache backend."

import time
try:
    import cPickle as pickle
except ImportError:
    import pickle

from django.core.cache.backends.base import BaseCache
from django.utils.synch import RWLock

class CacheClass(BaseCache):
    def __init__(self, _, params):
        BaseCache.__init__(self, params)
        self._cache = {}
        self._expire_info = {}

        max_entries = params.get('max_entries', 300)
        try:
            self._max_entries = int(max_entries)
        except (ValueError, TypeError):
            self._max_entries = 300

        cull_frequency = params.get('cull_frequency', 3)
        try:
            self._cull_frequency = int(cull_frequency)
        except (ValueError, TypeError):
            self._cull_frequency = 3

        self._lock = RWLock()

    def add(self, key, value, timeout=None):
        self._lock.writer_enters()
        try:
            exp = self._expire_info.get(key)
            if exp is None or exp <= time.time():
                try:
                    self._set(key, pickle.dumps(value), timeout)
                    return True
                except pickle.PickleError:
                    pass
            return False
        finally:
            self._lock.writer_leaves()

    def get(self, key, default=None):
        self._lock.reader_enters()
        try:
            exp = self._expire_info.get(key)
            if exp is None:
                return default
            elif exp > time.time():
                try:
                    return pickle.loads(self._cache[key])
                except pickle.PickleError:
                    return default
        finally:
            self._lock.reader_leaves()
        self._lock.writer_enters()
        try:
            del self._cache[key]
            del self._expire_info[key]
            return default
        finally:
            self._lock.writer_leaves()

    def _set(self, key, value, timeout=None):
        if len(self._cache) >= self._max_entries:
            self._cull()
        if timeout is None:
            timeout = self.default_timeout
        self._cache[key] = value
        self._expire_info[key] = time.time() + timeout

    def set(self, key, value, timeout=None):
        self._lock.writer_enters()
        # Python 2.3 and 2.4 don't allow combined try-except-finally blocks.
        try:
            try:
                self._set(key, pickle.dumps(value), timeout)
            except pickle.PickleError:
                pass
        finally:
            self._lock.writer_leaves()

    def has_key(self, key):
        self._lock.reader_enters()
        try:
            exp = self._expire_info.get(key)
            if exp is None:
                return False
            elif exp > time.time():
                return True
        finally:
            self._lock.reader_leaves()

        self._lock.writer_enters()
        try:
            del self._cache[key]
            del self._expire_info[key]
            return False
        finally:
            self._lock.writer_leaves()

    def _cull(self):
        if self._cull_frequency == 0:
            self._cache.clear()
            self._expire_info.clear()
        else:
            doomed = [k for (i, k) in enumerate(self._cache) if i % self._cull_frequency == 0]
            for k in doomed:
                self._delete(k)

    def _delete(self, key):
        try:
            del self._cache[key]
        except KeyError:
            pass
        try:
            del self._expire_info[key]
        except KeyError:
            pass

    def delete(self, key):
        self._lock.writer_enters()
        try:
            self._delete(key)
        finally:
            self._lock.writer_leaves()