Storage-backed versioned Block Structures: Configuration

common/djangoapps/request_cache/middleware.py

@@ -85,17 +85,10 @@ def request_cached(f):
         """
         Wrapper function to decorate with.
         """
-
-        # Build our cache key based on the module the function belongs to, the functions name, and a stringified
-        # list of arguments and a query string-style stringified list of keyword arguments.
-        converted_args = map(str, args)
-        converted_kwargs = map(str, reduce(list.__add__, map(list, sorted(kwargs.iteritems())), []))
-        cache_keys = [f.__module__, f.func_name] + converted_args + converted_kwargs
-        cache_key = '.'.join(cache_keys)
-
         # Check to see if we have a result in cache.  If not, invoke our wrapped
         # function.  Cache and return the result to the caller.
         rcache = RequestCache.get_request_cache()
+        cache_key = func_call_cache_key(f, *args, **kwargs)
 
         if cache_key in rcache.data:
             return rcache.data.get(cache_key)
@@ -105,4 +98,17 @@ def request_cached(f):
 
             return result
 
+    wrapper.request_cached_contained_func = f
     return wrapper
+
+
+def func_call_cache_key(func, *args, **kwargs):
+    """
+    Returns a cache key based on the function's module
+    the function's name, and a stringified list of arguments
+    and a query string-style stringified list of keyword arguments.
+    """
+    converted_args = map(str, args)
+    converted_kwargs = map(str, reduce(list.__add__, map(list, sorted(kwargs.iteritems())), []))
+    cache_keys = [func.__module__, func.func_name] + converted_args + converted_kwargs
+    return '.'.join(cache_keys)

openedx/core/djangoapps/content/block_structure/admin.py

@@ -0,0 +1,23 @@
+"""
+Django Admin for Block Structures.
+"""
+from django.contrib import admin
+
+from config_models.admin import ConfigurationModelAdmin
+from .config.models import BlockStructureConfiguration
+
+
+class BlockStructureAdmin(ConfigurationModelAdmin):
+    """
+    Configuration Admin for BlockStructureConfiguration.
+    """
+    def get_displayable_field_names(self):
+        """
+        Excludes unused 'enabled field from super's list.
+        """
+        displayable_field_names = super(BlockStructureAdmin, self).get_displayable_field_names()
+        displayable_field_names.remove('enabled')
+        return displayable_field_names
+
+
+admin.site.register(BlockStructureConfiguration, BlockStructureAdmin)

openedx/core/djangoapps/content/block_structure/config.py

@@ -1,28 +0,0 @@
-"""
-This module contains various configuration settings via
-waffle switches for the Block Structure framework.
-"""
-
-from waffle import switch_is_active
-
-
-INVALIDATE_CACHE_ON_PUBLISH = u'invalidate_cache_on_publish'
-STORAGE_BACKING_FOR_CACHE = u'storage_backing_for_cache'
-RAISE_ERROR_WHEN_NOT_FOUND = u'raise_error_when_not_found'
-
-
-def is_enabled(setting_name):
-    """
-    Returns whether the given setting is enabled.
-    """
-    return switch_is_active(
-        waffle_switch_name(setting_name)
-    )
-
-
-def waffle_switch_name(setting_name):
-    """
-    Returns the name of the waffle switch for the
-    given name of the setting.
-    """
-    return u'block_structure.{}'.format(setting_name)

openedx/core/djangoapps/content/block_structure/config/__init__.py

@@ -0,0 +1,47 @@
+"""
+This module contains various configuration settings via
+waffle switches for the Block Structure framework.
+"""
+from openedx.core.djangolib.waffle_utils import is_switch_enabled
+from request_cache.middleware import request_cached
+
+from .models import BlockStructureConfiguration
+
+
+INVALIDATE_CACHE_ON_PUBLISH = u'invalidate_cache_on_publish'
+STORAGE_BACKING_FOR_CACHE = u'storage_backing_for_cache'
+RAISE_ERROR_WHEN_NOT_FOUND = u'raise_error_when_not_found'
+PRUNE_OLD_VERSIONS = u'prune_old_versions'
+
+
+def is_enabled(setting_name):
+    """
+    Returns whether the given block_structure setting
+    is enabled.
+    """
+    bs_waffle_name = _bs_waffle_switch_name(setting_name)
+    return is_switch_enabled(bs_waffle_name)
+
+
+@request_cached
+def num_versions_to_keep():
+    """
+    Returns and caches the current setting for num_versions_to_keep.
+    """
+    return BlockStructureConfiguration.current().num_versions_to_keep
+
+
+@request_cached
+def cache_timeout_in_seconds():
+    """
+    Returns and caches the current setting for cache_timeout_in_seconds.
+    """
+    return BlockStructureConfiguration.current().cache_timeout_in_seconds
+
+
+def _bs_waffle_switch_name(setting_name):
+    """
+    Returns the name of the waffle switch for the
+    given block structure setting.
+    """
+    return u'block_structure.{}'.format(setting_name)

openedx/core/djangoapps/content/block_structure/config/models.py

@@ -0,0 +1,26 @@
+"""
+Models for configuration of Block Structures.
+"""
+from django.db.models import IntegerField
+from config_models.models import ConfigurationModel
+
+
+class BlockStructureConfiguration(ConfigurationModel):
+    """
+    Configuration model for Block Structures.
+    """
+    DEFAULT_PRUNE_KEEP_COUNT = 5
+    DEFAULT_CACHE_TIMEOUT_IN_SECONDS = 60 * 60 * 24  # 24 hours
+
+    class Meta(object):
+        app_label = 'block_structure'
+        db_table = 'block_structure_config'
+
+    num_versions_to_keep = IntegerField(blank=True, null=True, default=DEFAULT_PRUNE_KEEP_COUNT)
+    cache_timeout_in_seconds = IntegerField(blank=True, null=True, default=DEFAULT_CACHE_TIMEOUT_IN_SECONDS)
+
+    def __unicode__(self):
+        return u"BlockStructureConfiguration: num_versions_to_keep: {}, cache_timeout_in_seconds: {}".format(
+            self.num_versions_to_keep,
+            self.cache_timeout_in_seconds,
+        )

openedx/core/djangoapps/content/block_structure/migrations/0001_config.py

@@ -0,0 +1,30 @@
+# -*- coding: utf-8 -*-
+from __future__ import unicode_literals
+
+from django.db import migrations, models
+import django.db.models.deletion
+from django.conf import settings
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        migrations.swappable_dependency(settings.AUTH_USER_MODEL),
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name='BlockStructureConfiguration',
+            fields=[
+                ('id', models.AutoField(verbose_name='ID', serialize=False, auto_created=True, primary_key=True)),
+                ('change_date', models.DateTimeField(auto_now_add=True, verbose_name='Change date')),
+                ('enabled', models.BooleanField(default=False, verbose_name='Enabled')),
+                ('num_versions_to_keep', models.IntegerField(default=5, null=True, blank=True)),
+                ('cache_timeout_in_seconds', models.IntegerField(default=86400, null=True, blank=True)),
+                ('changed_by', models.ForeignKey(on_delete=django.db.models.deletion.PROTECT, editable=False, to=settings.AUTH_USER_MODEL, null=True, verbose_name='Changed by')),
+            ],
+            options={
+                'db_table': 'block_structure_config',
+            },
+        ),
+    ]

openedx/core/djangoapps/content/block_structure/tests/helpers.py

@@ -3,7 +3,10 @@ Helpers for Course Blocks tests.
 """
 
 from openedx.core.lib.block_structure.cache import BlockStructureCache
+from openedx.core.djangolib.testing.waffle_utils import override_switch
+
 from ..api import get_cache
+from ..config import _bs_waffle_switch_name
 
 
 def is_course_in_block_structure_cache(course_key, store):
@@ -12,3 +15,15 @@ def is_course_in_block_structure_cache(course_key, store):
     """
     course_usage_key = store.make_course_usage_key(course_key)
     return BlockStructureCache(get_cache()).get(course_usage_key) is not None
+
+
+class override_config_setting(override_switch):  # pylint:disable=invalid-name
+    """
+    Subclasses override_switch to use the block structure
+    name-spaced switch names.
+    """
+    def __init__(self, name, active):
+        super(override_config_setting, self).__init__(
+            _bs_waffle_switch_name(name),
+            active
+        )

openedx/core/djangoapps/content/block_structure/tests/test_signals.py

@@ -3,7 +3,6 @@ Unit tests for the Course Blocks signals
 """
 import ddt
 from mock import patch
-from waffle.testutils import override_switch
 
 from opaque_keys.edx.locator import LibraryLocator, CourseLocator
 from xmodule.modulestore.exceptions import ItemNotFoundError
@@ -11,9 +10,9 @@ from xmodule.modulestore.tests.django_utils import ModuleStoreTestCase
 from xmodule.modulestore.tests.factories import CourseFactory
 
 from ..api import get_block_structure_manager
+from ..config import INVALIDATE_CACHE_ON_PUBLISH
 from ..signals import _listen_for_course_publish
-from ..config import INVALIDATE_CACHE_ON_PUBLISH, waffle_switch_name
-from .helpers import is_course_in_block_structure_cache
+from .helpers import is_course_in_block_structure_cache, override_config_setting
 
 
 @ddt.ddt
@@ -55,7 +54,7 @@ class CourseBlocksSignalTest(ModuleStoreTestCase):
     def test_cache_invalidation(self, invalidate_cache_enabled, mock_bs_manager_clear):
         test_display_name = "Jedi 101"
 
-        with override_switch(waffle_switch_name(INVALIDATE_CACHE_ON_PUBLISH), active=invalidate_cache_enabled):
+        with override_config_setting(INVALIDATE_CACHE_ON_PUBLISH, active=invalidate_cache_enabled):
             self.course.display_name = test_display_name
             self.store.update_item(self.course, self.user.id)
 

openedx/core/djangolib/testing/tests/test_utils.py

@@ -5,9 +5,9 @@ from django.contrib.auth import get_user_model
 from django.contrib.auth.models import AnonymousUser
 from django.http.request import HttpRequest
 from django.test import TestCase
-from waffle.models import Switch
 
-from ..utils import get_mock_request, toggle_switch
+from ..utils import get_mock_request
+
 
 USER_MODEL = get_user_model()
 
@@ -28,27 +28,3 @@ class TestGetMockRequest(TestCase):
     def test_mock_request_without_user(self):
         request = get_mock_request()
         self.assertIsInstance(request.user, AnonymousUser)
-
-
-class TestToggleSwitch(TestCase):
-    """
-    Verify that the toggle_switch utility can be used to turn Waffle Switches
-    on and off.
-    """
-    def test_toggle_switch(self):
-        """Verify that a new switch can be turned on and off."""
-        name = 'foo'
-
-        switch = toggle_switch(name)
-
-        # Verify that the switch was saved.
-        self.assertEqual(switch, Switch.objects.get())
-
-        # Verify that the switch has the right name and is active.
-        self.assertEqual(switch.name, name)
-        self.assertTrue(switch.active)
-
-        switch = toggle_switch(name)
-
-        # Verify that the switch has been turned off.
-        self.assertFalse(switch.active)

openedx/core/djangolib/testing/utils.py

@@ -190,25 +190,3 @@ def skip_unless_lms(func):
     Only run the decorated test in the LMS test suite
     """
     return skipUnless(settings.ROOT_URLCONF == 'lms.urls', 'Test only valid in LMS')(func)
-
-
-def toggle_switch(name, active=True):
-    """
-    Activate or deactivate a Waffle switch. The switch is created if it does not exist.
-
-    Arguments:
-        name (str): Name of the switch to be toggled.
-
-    Keyword Arguments:
-        active (bool): Whether a newly created switch should be on or off.
-
-    Returns:
-        Switch
-    """
-    switch, created = Switch.objects.get_or_create(name=name, defaults={'active': active})
-
-    if not created:
-        switch.active = not switch.active
-        switch.save()
-
-    return switch

openedx/core/djangolib/testing/waffle_utils.py

@@ -0,0 +1,27 @@
+"""
+Test utilities when using waffle.
+"""
+from waffle.testutils import override_switch as waffle_override_switch
+from request_cache.middleware import RequestCache, func_call_cache_key
+from ..waffle_utils import is_switch_enabled
+
+
+class override_switch(waffle_override_switch):  # pylint:disable=invalid-name
+    """
+    Subclasses waffle's override_switch in order clear the cache
+    used on the is_switch_enabled function.
+    """
+    def _clear_cache(self):
+        """
+        Clears the requestcached values on the is_switch_enabled function.
+        """
+        cache_key = func_call_cache_key(is_switch_enabled.request_cached_contained_func, self.name)
+        RequestCache.get_request_cache().data.pop(cache_key, None)
+
+    def __enter__(self):
+        self._clear_cache()
+        super(override_switch, self).__enter__()
+
+    def __exit__(self, *args, **kwargs):
+        self._clear_cache()
+        super(override_switch, self).__exit__(*args, **kwargs)

openedx/core/djangolib/waffle_utils.py

@@ -0,0 +1,15 @@
+"""
+Utilities for waffle usage.
+"""
+from request_cache.middleware import request_cached
+from waffle import switch_is_active
+
+
+@request_cached
+def is_switch_enabled(waffle_name):
+    """
+    Returns and caches whether the given waffle switch is enabled.
+    See testing.waffle_utils.override_config_setting for a
+    helper to override and clear the cache during tests.
+    """
+    return switch_is_active(waffle_name)