fixed error message about cache settings

rhodecode/model/caching_query.py

@@ -1,275 +1,276
 """caching_query.py
 
 Represent persistence structures which allow the usage of
 Beaker caching with SQLAlchemy.
 
 The three new concepts introduced here are:
 
  * CachingQuery - a Query subclass that caches and
    retrieves results in/from Beaker.
  * FromCache - a query option that establishes caching
    parameters on a Query
  * RelationshipCache - a variant of FromCache which is specific
    to a query invoked during a lazy load.
  * _params_from_query - extracts value parameters from 
    a Query.
 
 The rest of what's here are standard SQLAlchemy and
 Beaker constructs.
    
 """
 from beaker.exceptions import BeakerException
 from sqlalchemy.orm.interfaces import MapperOption
 from sqlalchemy.orm.query import Query
 from sqlalchemy.sql import visitors
 import beaker
 
 class CachingQuery(Query):
     """A Query subclass which optionally loads full results from a Beaker 
     cache region.
     
     The CachingQuery stores additional state that allows it to consult
     a Beaker cache before accessing the database:
     
     * A "region", which is a cache region argument passed to a 
       Beaker CacheManager, specifies a particular cache configuration
       (including backend implementation, expiration times, etc.)
     * A "namespace", which is a qualifying name that identifies a
       group of keys within the cache.  A query that filters on a name 
       might use the name "by_name", a query that filters on a date range 
       to a joined table might use the name "related_date_range".
       
     When the above state is present, a Beaker cache is retrieved.
     
     The "namespace" name is first concatenated with 
     a string composed of the individual entities and columns the Query 
     requests, i.e. such as ``Query(User.id, User.name)``.
     
     The Beaker cache is then loaded from the cache manager based
     on the region and composed namespace.  The key within the cache
     itself is then constructed against the bind parameters specified
     by this query, which are usually literals defined in the 
     WHERE clause.
 
     The FromCache and RelationshipCache mapper options below represent
     the "public" method of configuring this state upon the CachingQuery.
     
     """
     
     def __init__(self, manager, *args, **kw):
         self.cache_manager = manager
         Query.__init__(self, *args, **kw)
         
     def __iter__(self):
         """override __iter__ to pull results from Beaker
            if particular attributes have been configured.
            
            Note that this approach does *not* detach the loaded objects from
            the current session. If the cache backend is an in-process cache
            (like "memory") and lives beyond the scope of the current session's
            transaction, those objects may be expired. The method here can be
            modified to first expunge() each loaded item from the current
            session before returning the list of items, so that the items
            in the cache are not the same ones in the current Session.
            
         """
         if hasattr(self, '_cache_parameters'):
             return self.get_value(createfunc=lambda: list(Query.__iter__(self)))
         else:
             return Query.__iter__(self)
 
     def invalidate(self):
         """Invalidate the value represented by this Query."""
 
         cache, cache_key = _get_cache_parameters(self)
         cache.remove(cache_key)
 
     def get_value(self, merge=True, createfunc=None):
         """Return the value from the cache for this query.
 
         Raise KeyError if no value present and no
         createfunc specified.
 
         """
         cache, cache_key = _get_cache_parameters(self)
         ret = cache.get_value(cache_key, createfunc=createfunc)
         if merge:
             ret = self.merge_result(ret, load=False)
         return ret
 
     def set_value(self, value):
         """Set the value in the cache for this query."""
 
         cache, cache_key = _get_cache_parameters(self)
         cache.put(cache_key, value)        
 
 def query_callable(manager):
     def query(*arg, **kw):
         return CachingQuery(manager, *arg, **kw)
     return query
 
 def get_cache_region(name, region):
         if region not in beaker.cache.cache_regions:
-            raise BeakerException('Cache region not configured: %s' % region)
+        raise BeakerException('Cache region not configured: %s'
+            'Check if proper cache settings are in the .ini files' % region)
         kw = beaker.cache.cache_regions[region]
         return beaker.cache.Cache._get_cache(name, kw)
         
 def _get_cache_parameters(query):
     """For a query with cache_region and cache_namespace configured,
     return the correspoinding Cache instance and cache key, based
     on this query's current criterion and parameter values.
 
     """
     if not hasattr(query, '_cache_parameters'):
         raise ValueError("This Query does not have caching parameters configured.")
 
     region, namespace, cache_key = query._cache_parameters
     
     namespace = _namespace_from_query(namespace, query)
 
     if cache_key is None:
         # cache key - the value arguments from this query's parameters.
         args = _params_from_query(query)
         cache_key = " ".join([str(x) for x in args])
 
     # get cache
     #cache = query.cache_manager.get_cache_region(namespace, region)
     cache = get_cache_region(namespace, region)
     # optional - hash the cache_key too for consistent length
     # import uuid
     # cache_key= str(uuid.uuid5(uuid.NAMESPACE_DNS, cache_key))
 
     return cache, cache_key
 
 def _namespace_from_query(namespace, query):
     # cache namespace - the token handed in by the 
     # option + class we're querying against
     namespace = " ".join([namespace] + [str(x) for x in query._entities])
 
     # memcached wants this
     namespace = namespace.replace(' ', '_')
 
     return namespace
 
 def _set_cache_parameters(query, region, namespace, cache_key):
     
     if hasattr(query, '_cache_parameters'):
         region, namespace, cache_key = query._cache_parameters
         raise ValueError("This query is already configured "
                         "for region %r namespace %r" % 
                         (region, namespace)
                     )
     query._cache_parameters = region, namespace, cache_key
     
 class FromCache(MapperOption):
     """Specifies that a Query should load results from a cache."""
 
     propagate_to_loaders = False
 
     def __init__(self, region, namespace, cache_key=None):
         """Construct a new FromCache.
         
         :param region: the cache region.  Should be a
         region configured in the Beaker CacheManager.
         
         :param namespace: the cache namespace.  Should
         be a name uniquely describing the target Query's
         lexical structure.
         
         :param cache_key: optional.  A string cache key 
         that will serve as the key to the query.   Use this
         if your query has a huge amount of parameters (such
         as when using in_()) which correspond more simply to 
         some other identifier.
 
         """
         self.region = region
         self.namespace = namespace
         self.cache_key = cache_key
     
     def process_query(self, query):
         """Process a Query during normal loading operation."""
         
         _set_cache_parameters(query, self.region, self.namespace, self.cache_key)
 
 class RelationshipCache(MapperOption):
     """Specifies that a Query as called within a "lazy load" 
        should load results from a cache."""
 
     propagate_to_loaders = True
 
     def __init__(self, region, namespace, attribute):
         """Construct a new RelationshipCache.
         
         :param region: the cache region.  Should be a
         region configured in the Beaker CacheManager.
         
         :param namespace: the cache namespace.  Should
         be a name uniquely describing the target Query's
         lexical structure.
         
         :param attribute: A Class.attribute which
         indicates a particular class relationship() whose
         lazy loader should be pulled from the cache.
         
         """
         self.region = region
         self.namespace = namespace
         self._relationship_options = {
             (attribute.property.parent.class_, attribute.property.key) : self
         }
 
     def process_query_conditionally(self, query):
         """Process a Query that is used within a lazy loader.
 
         (the process_query_conditionally() method is a SQLAlchemy
         hook invoked only within lazyload.)
 
         """
         if query._current_path:
             mapper, key = query._current_path[-2:]
 
             for cls in mapper.class_.__mro__:
                 if (cls, key) in self._relationship_options:
                     relationship_option = self._relationship_options[(cls, key)]
                     _set_cache_parameters(
                             query,
                             relationship_option.region,
                             relationship_option.namespace,
                             None)
 
     def and_(self, option):
         """Chain another RelationshipCache option to this one.
         
         While many RelationshipCache objects can be specified on a single
         Query separately, chaining them together allows for a more efficient
         lookup during load.
         
         """
         self._relationship_options.update(option._relationship_options)
         return self
 
 
 def _params_from_query(query):
     """Pull the bind parameter values from a query.
     
     This takes into account any scalar attribute bindparam set up.
     
     E.g. params_from_query(query.filter(Cls.foo==5).filter(Cls.bar==7)))
     would return [5, 7].
     
     """
     v = []
     def visit_bindparam(bind):
         value = query._params.get(bind.key, bind.value)
         
         # lazyloader may dig a callable in here, intended
         # to late-evaluate params after autoflush is called.
         # convert to a scalar value.
         if callable(value):
             value = value()
             
         v.append(value)
     if query._criterion is not None:
         visitors.traverse(query._criterion, {}, {'bindparam':visit_bindparam})
     return v