Get rid of duplicate code, fixing a big performance problem in the pr…

…ocess

docs/api.rst

@@ -10,6 +10,12 @@ Context / Registry
 .. autoclass:: libres.context.context.Context
     :members:
 
+.. autoclass:: libres.context.context.ContextServicesMixin
+    :members:
+
+.. autoclass:: libres.context.context.StoppableService
+    :members:
+
 Database Access
 ---------------
 

libres/context/context.py

@@ -1,6 +1,7 @@
 import libres
 import threading
 
+from cached_property import cached_property
 from contextlib import contextmanager
 from libres.modules import errors
 
@@ -22,6 +23,40 @@ def stop_service(self):
         pass
 
 
+class ContextServicesMixin(object):
+    """ Provides access methods to the context's services. Expects
+    the class that uses the mixin to provide self.context.
+
+    The results are cached for performance.
+
+    """
+
+    @cached_property
+    def is_allocation_exposed(self):
+        return self.context.get_service('exposure').is_allocation_exposed
+
+    @cached_property
+    def generate_uuid(self):
+        return self.context.get_service('uuid_generator')
+
+    @cached_property
+    def validate_email(self):
+        return self.context.get_service('email_validator')
+
+    def clear_cache(self):
+        """ Clears the cache of the mixin. """
+
+        properties = (
+            'is_allocation_exposed',
+            'generate_uuid',
+            'validate_email'
+        )
+
+        for p in properties:
+            if p in self.__dict__:
+                del self.__dict__[p]
+
+
 class Context(object):
     """ Used throughout Libres, the context holds settings like the database
     connection string and services like the json dumps/loads functions that
@@ -40,6 +75,12 @@ class Context(object):
     master_context is used instead. In other words, the custom context
     inherits from the master context.
 
+    Note that contexts not meant to be changed often. Classes talking to the
+    database usually cache data form the context freely. That means basically
+    that after changing the context you should get a fresh
+    :class:`~libres.db.scheduler.Scheduler` instance or call
+    :meth:`~.ContextServicesMixin.clear_cache`.
+
     A context may be registered as follows::
 
         from libres import registry

libres/db/queries.py

@@ -10,10 +10,11 @@
 
 from libres.modules import errors, events, calendar
 from libres.db.models import Allocation, Reservation, ReservedSlot
+from libres.context.context import ContextServicesMixin
 from libres.context.session import serialized, Serializable
 
 
-class Queries(Serializable):
+class Queries(Serializable, ContextServicesMixin):
     """ Contains helper methods independent of the resource (as owned by
     :class:`.scheduler.Scheduler`)
 
@@ -31,12 +32,6 @@ def all_allocations_in_range(self, start, end):
             self.session.query(Allocation), start, end
         )
 
-    @property
-    def is_allocation_exposed(self):
-        # XXX this is copied over from the Scheduler. A ContextServicesMixin
-        # could be responsible for this in a single class
-        return self.context.get_service('exposure').is_allocation_exposed
-
     @staticmethod
     def allocations_in_range(query, start, end):
         """ Takes an allocation query and limits it to the allocations

libres/db/scheduler.py

@@ -1,5 +1,6 @@
 from datetime import datetime, timedelta
 
+from libres.context.context import ContextServicesMixin
 from libres.context.session import serialized, Serializable
 from libres.db.models import ORMBase, Allocation, ReservedSlot, Reservation
 from libres.db.queries import Queries
@@ -19,7 +20,7 @@
 missing = object()
 
 
-class Scheduler(Serializable):
+class Scheduler(Serializable, ContextServicesMixin):
     """ The Scheduler is responsible for talking to the backend of the given
     context to create reservations. It is the main part of the API.
     """
@@ -74,7 +75,7 @@ def resource(self):
         on the namespace uuid defined in :ref:`settings.uuid_namespace`
 
         """
-        return self.context.get_service('uuid_generator')(self.name)
+        return self.generate_uuid(self.name)
 
     def prepare_date(self, date):
         return calendar.normalize_date(date, self.timezone)
@@ -92,14 +93,6 @@ def prepare_range(self, start, end):
     def setup_database(self):
         ORMBase.metadata.create_all(self.session.bind)
 
-    @property
-    def validate_email(self):
-        return self.context.get_service('email_validator')
-
-    @property
-    def is_allocation_exposed(self):
-        return self.context.get_service('exposure').is_allocation_exposed
-
     def managed_allocations(self):
         """ The allocations managed by this scheduler / resource. """
         query = self.session.query(Allocation)

libres/tests/test_scheduler.py

@@ -1523,7 +1523,7 @@ def test_search_allocations(scheduler):
     assert len(scheduler.search_allocations(*daterange, days=['su'])) == 1
     assert len(scheduler.search_allocations(*daterange, days=['mo'])) == 0
 
-    # make sure the exposure is taken into account
+    # make sure the exposure is taken into account..
     class MockExposure(object):
 
         def __init__(self, return_value):
@@ -1533,9 +1533,11 @@ def is_allocation_exposed(self, allocation):
             return self.return_value
 
     scheduler.context.set_service('exposure', lambda ctx: MockExposure(False))
+    scheduler.clear_cache()
     assert len(scheduler.search_allocations(*daterange)) == 0
 
     scheduler.context.set_service('exposure', lambda ctx: MockExposure(True))
+    scheduler.clear_cache()
     assert len(scheduler.search_allocations(*daterange)) == 1
 
     # test available only