add support of new parameters for memcached client

git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@27580 20353a03-c40f-0410-a6d1-a30d3c3de9de

product/ERP5Type/CachePlugins/DistributedRamCache.py

@@ -39,7 +39,6 @@ import zope.interface
 
 try:
   import memcache
-  MEMCACHED_SERVER_MAX_KEY_LENGTH = memcache.SERVER_MAX_KEY_LENGTH
 except ImportError:
   LOG('DistributedRamCache', 0, 'unable to import memcache')
 
@@ -55,7 +54,9 @@ class DistributedRamCache(BaseCache):
 
   def __init__(self, params={}):
     self._servers = params.get('server', '')
-    self._debugLevel = params.get('debugLevel', 0)
+    self._server_max_key_length = params.get('server_max_key_length', 250)
+    self._server_max_value_length = params.get('server_max_value_length', 1024*1024)
+    self._debug_level = params.get('debug_level', 0)
     BaseCache.__init__(self)
 
   def initCacheStorage(self):
@@ -74,9 +75,12 @@ class DistributedRamCache(BaseCache):
     memcache_conn = connection_pool.get(thread_id, None)
     if memcache_conn is None:
       ## we don't have memcache_conn for this thread
-      memcache_conn = memcache.Client(self._servers.split('\n'), debug=self._debugLevel)
+      memcache_conn = memcache.Client(self._servers.split('\n'),
+                              debug=self._debug_level,
+                              server_max_key_length=self._server_max_key_length,
+                              server_max_value_length=self._server_max_value_length)
       connection_pool[thread_id] =  memcache_conn
-      return memcache_conn      
+      return memcache_conn
     else:
       ## we have memcache_conn for this thread
       return memcache_conn
@@ -84,24 +88,28 @@ class DistributedRamCache(BaseCache):
   def checkAndFixCacheId(self, cache_id, scope):
     ## memcached doesn't support namespaces (cache scopes) so to "emmulate"
     ## such behaviour when constructing cache_id we add scope in front
-    cache_id = "%s.%s" %(scope, cache_id) 
-    ## memcached will fail to store cache_id longer than MEMCACHED_SERVER_MAX_KEY_LENGTH.
-    return cache_id[:MEMCACHED_SERVER_MAX_KEY_LENGTH]
+    cache_id = "%s.%s" %(scope, cache_id)
+    if self._server_max_key_length != 0:
+      ## memcached will fail to store cache_id longer than MEMCACHED_SERVER_MAX_KEY_LENGTH.
+      return cache_id[:self._server_max_key_length]
+    return cache_id
 
   def get(self, cache_id, scope, default=None):
     cache_storage = self.getCacheStorage()
     cache_id = self.checkAndFixCacheId(cache_id, scope)
     cache_entry = cache_storage.get(cache_id)
-    self.markCacheHit()
-    return cache_entry
-
-  def set(self, cache_id, scope, value, cache_duration= None, calculation_time=0):
+    if cache_entry is not None:
+      # since some memcached-like products don't support expiration, we
+      # check it by ourselves.
+      if cache_entry.isExpired():
+        cache_storage.delete(cache_id)
+        return default
+      self.markCacheHit()
+    return cache_entry or default
+
+  def set(self, cache_id, scope, value, cache_duration=None, calculation_time=0):
     cache_storage = self.getCacheStorage()
     cache_id = self.checkAndFixCacheId(cache_id, scope)
-    if cache_duration is None:
-      ## what should be default cache_duration when None is specified?
-      ## currently when 'None' it means forever so give it  big value of 24 hours
-      cache_duration = 86400
     cache_entry = CacheEntry(value, cache_duration, calculation_time)
     cache_storage.set(cache_id, cache_entry, cache_duration)
     self.markCacheMiss()
@@ -114,7 +122,7 @@ class DistributedRamCache(BaseCache):
     ## The workaround of this problem is to create a new connection for every cache access
     ## but that's too much overhead or create a new connection when cache is to be expired. 
     ## This way we can catch memcached server failures. BTW: This hack is forced by the lack functionality in python-memcached 
-    #self._cache = memcache.Client(self._servers.split('\n'), debug=self._debugLevel) 
+    #self._cache = memcache.Client(self._servers.split('\n'), debug=self._debug_level) 
     pass
 
   def delete(self, cache_id, scope):