Allow to override cache implementation

issue5962
review33491003

CHANGELOG

@@ -1,3 +1,4 @@
+* Allow to override cache implementation
 * Add button rule
 * Allow to specify translatable languages in trytond-admin
 * Add datetime_field on Reference

doc/ref/cache.rst

@@ -0,0 +1,50 @@
+.. _ref-cache:
+.. module:: trytond.cache
+
+=====
+Cache
+=====
+
+.. class:: Cache(name[, size_limit[, context]])
+
+The class is used to cache values between server requests. The `name` should
+be unique and it's used to identify the cache. We usually use
+`<class_name>.<content_name>` to make it unique. The `size_limit` field can
+be used to limit the number of values cached and the `context` parameter
+is used to indicate if the cache depends on the user context and is true
+by default.
+
+.. method:: get(key[, default])
+
+Retrieve the value of the key in the cache. If a `default` is specified it
+will be returned when the key is missing otherwise it will return `None`.
+
+.. method:: set(key, value)
+
+Sets the `value` of the `key` in the cache.
+
+.. method:: clear()
+
+Clears all the keys in the cache.
+
+.. staticmethod:: clean(dbname)
+
+Clean the cache for database `dbname`
+
+.. staticmethod:: reset(dbname, name)
+
+Reset the `name` cache for database `dbname`
+
+.. staticmethod:: resets(dbname)
+
+Resets all the caches stored for database `dbname`
+
+.. staticmethod:: drop(dbname)
+
+Drops all the caches for database `dbname`
+
+.. note::
+    By default Tryton uses a MemoryCache, but this behaviour can be overridden
+    by setting a fully qualified name of an alternative class defined in the
+    configuration `class` of the `cache` section.
+..

doc/ref/index.rst

@@ -16,3 +16,4 @@ API Reference
     rpc
     sendmail
     filestore
+    cache

trytond/cache.py

@@ -6,9 +6,11 @@ from collections import OrderedDict
 from sql import Table
 from sql.functions import CurrentTimestamp
 
+from trytond.config import config
 from trytond.transaction import Transaction
+from trytond.tools import resolve
 
-__all__ = ['Cache', 'LRUDict']
+__all__ = ['BaseCache', 'Cache', 'LRUDict']
 
 
 def freeze(o):
@@ -20,28 +22,59 @@ def freeze(o):
         return o
 
 
-class Cache(object):
-    """
-    A key value LRU cache with size limit.
-    """
+class BaseCache(object):
     _cache_instance = []
-    _resets = {}
-    _resets_lock = Lock()
 
     def __init__(self, name, size_limit=1024, context=True):
+        self._name = name
         self.size_limit = size_limit
         self.context = context
-        self._cache = {}
         self._cache_instance.append(self)
-        self._name = name
-        self._timestamp = None
-        self._lock = Lock()
 
     def _key(self, key):
         if self.context:
             return (key, Transaction().user, freeze(Transaction().context))
         return key
 
+    def get(self, key, default=None):
+        raise NotImplemented
+
+    def set(self, key, value):
+        raise NotImplemented
+
+    def clear(self):
+        raise NotImplemented
+
+    @staticmethod
+    def clean(dbname):
+        raise NotImplemented
+
+    @staticmethod
+    def reset(dbname, name):
+        raise NotImplemented
+
+    @staticmethod
+    def resets(dbname):
+        raise NotImplemented
+
+    @classmethod
+    def drop(cls, dbname):
+        raise NotImplemented
+
+
+class MemoryCache(BaseCache):
+    """
+    A key value LRU cache with size limit.
+    """
+    _resets = {}
+    _resets_lock = Lock()
+
+    def __init__(self, name, size_limit=1024, context=True):
+        super(MemoryCache, self).__init__(name, size_limit, context)
+        self._cache = {}
+        self._timestamp = None
+        self._lock = Lock()
+
     def get(self, key, default=None):
         dbname = Transaction().database.name
         key = self._key(key)
@@ -119,6 +152,11 @@ class Cache(object):
         for inst in cls._cache_instance:
             inst._cache.pop(dbname, None)
 
+if config.get('cache', 'class'):
+    Cache = resolve(config.get('cache', 'class'))
+else:
+    Cache = MemoryCache
+
 
 class LRUDict(OrderedDict):
     """