def _update_cache(cls, user_id, course_key, visible_blocks):
"""
Adds a specific set of visible blocks to the request cache.
This assumes that prefetch has already been called.
"""
get_cache(cls._CACHE_NAMESPACE)[cls._cache_key(user_id, course_key)].update(
{visible_block.hashed: visible_block for visible_block in visible_blocks}
)
def _update_cache(cls, course_key, visible_blocks):
"""
Adds a specific set of visible blocks to the request cache.
This assumes that prefetch has already been called.
"""
get_cache(cls._CACHE_NAMESPACE)[cls._cache_key(course_key)].update(
{visible_block.hashed: visible_block for visible_block in visible_blocks}
)
def __enter__(self):
connection = transaction.get_connection(self.using)
cache = get_cache(OUTER_ATOMIC_CACHE_NAME)
# By default it is enabled.
enable = True
# If name is set it is only enabled if requested by calling enable_named_outer_atomic().
if self.name:
enable = cache.get(self.name, False)
if enable:
# TestCase setup nests tests in two atomics - one for the test class and one for the individual test.
# The outermost atomic starts a transaction - so does not have a savepoint.
# The inner atomic starts a savepoint around the test.
# So, for tests only, there should be exactly one savepoint_id and two atomic_for_testcase_calls.
# atomic_for_testcase_calls below is added in a monkey-patch for tests only.
if self.ALLOW_NESTED and (self.atomic_for_testcase_calls - len(connection.savepoint_ids)) < 1:
raise transaction.TransactionManagementError('Cannot be inside an atomic block.')
# Otherwise, this shouldn't be nested in any atomic block.
if not self.ALLOW_NESTED and connection.in_atomic_block:
raise transaction.TransactionManagementError('Cannot be inside an atomic block.')
# This will set the transaction isolation level to READ COMMITTED for the next transaction.
if self.read_committed is True:
if connection.vendor == 'mysql':
cursor = connection.cursor()
cursor.execute("SET TRANSACTION ISOLATION LEVEL READ COMMITTED")
super(OuterAtomic, self).__enter__()
def get_course_content_milestones(course_id, content_id=None, relationship='requires', user_id=None):
"""
Client API operation adapter/wrapper
Uses the request cache to store all of a user's
milestones
Returns all content blocks in a course if content_id is None, otherwise it just returns that
specific content block.
"""
if not settings.FEATURES.get('MILESTONES_APP'):
return []
if user_id is None:
return milestones_api.get_course_content_milestones(course_id, content_id, relationship)
request_cache_dict = get_cache(REQUEST_CACHE_NAME)
if user_id not in request_cache_dict:
request_cache_dict[user_id] = {}
if relationship not in request_cache_dict[user_id]:
request_cache_dict[user_id][relationship] = milestones_api.get_course_content_milestones(
course_key=course_id,
relationship=relationship,
user={"id": user_id}
)
if content_id is None:
return request_cache_dict[user_id][relationship]
return [m for m in request_cache_dict[user_id][relationship] if m['content_id'] == unicode(content_id)]
def get_group_info_for_cohort(cohort, use_cached=False):
"""
Get the ids of the group and partition to which this cohort has been linked
as a tuple of (int, int).
If the cohort has not been linked to any group/partition, both values in the
tuple will be None.
The partition group info is cached for the duration of a request. Pass
use_cached=True to use the cached value instead of fetching from the
database.
"""
cache = get_cache(u"cohorts.get_group_info_for_cohort")
cache_key = unicode(cohort.id)
if use_cached and cache_key in cache:
return cache[cache_key]
cache.pop(cache_key, None)
try:
partition_group = CourseUserGroupPartitionGroup.objects.get(
course_user_group=cohort)
return cache.setdefault(
cache_key,
(partition_group.group_id, partition_group.partition_id))
except CourseUserGroupPartitionGroup.DoesNotExist:
pass
return cache.setdefault(cache_key, (None, None))
def get_group_info_for_cohort(cohort, use_cached=False):
"""
Get the ids of the group and partition to which this cohort has been linked
as a tuple of (int, int).
If the cohort has not been linked to any group/partition, both values in the
tuple will be None.
The partition group info is cached for the duration of a request. Pass
use_cached=True to use the cached value instead of fetching from the
database.
"""
cache = get_cache(u"cohorts.get_group_info_for_cohort")
cache_key = unicode(cohort.id)
if use_cached and cache_key in cache:
return cache[cache_key]
cache.pop(cache_key, None)
try:
partition_group = CourseUserGroupPartitionGroup.objects.get(course_user_group=cohort)
return cache.setdefault(cache_key, (partition_group.group_id, partition_group.partition_id))
except CourseUserGroupPartitionGroup.DoesNotExist:
pass
return cache.setdefault(cache_key, (None, None))
def cached_get_or_create(cls, user_id, blocks):
"""
Given a ``user_id`` and a ``BlockRecordList`` object, attempts to
fetch the related VisibleBlocks model from the request cache. This
will create and save a new ``VisibleBlocks`` record if no record
exists corresponding to the hash_value of ``blocks``.
"""
prefetched = get_cache(cls._CACHE_NAMESPACE).get(
cls._cache_key(user_id, blocks.course_key))
if prefetched is not None:
model = prefetched.get(blocks.hash_value)
if not model:
# We still have to do a get_or_create, because
# another user may have had this block hash created,
# even if the user we checked the cache for hasn't yet.
model, _ = cls.objects.get_or_create(
hashed=blocks.hash_value,
blocks_json=blocks.json_value,
course_id=blocks.course_key,
)
cls._update_cache(user_id, blocks.course_key, [model])
else:
model, _ = cls.objects.get_or_create(
hashed=blocks.hash_value,
defaults={
u'blocks_json': blocks.json_value,
u'course_id': blocks.course_key
},
)
return model
def user_timezone_locale_prefs(request):
"""
Checks if request has an authenticated user.
If so, sends set (or none if unset) time_zone and language prefs.
This interacts with the DateUtils to either display preferred or attempt to determine
system/browser set time_zones and languages
"""
cached_value = get_cache(CACHE_NAME)
if not cached_value:
user_prefs = {
'user_timezone': None,
'user_language': None,
}
if hasattr(request, 'user') and request.user.is_authenticated():
try:
user_preferences = get_user_preferences(request.user)
except (UserNotFound, UserAPIInternalError):
cached_value.update(user_prefs)
else:
user_prefs = {
key: user_preferences.get(pref_name, None)
for key, pref_name in RETRIEVABLE_PREFERENCES.iteritems()
}
cached_value.update(user_prefs)
return cached_value
def process_response(self, __, response):
"""
If request is from mobile native app, then add version related info to response headers.
Returns:
Http response: with additional headers;
1. EDX-APP-LATEST-VERSION; if user app version < latest available version
2. EDX-APP-VERSION-LAST-SUPPORTED-DATE; if user app version < min supported version and
timestamp < expiry of that version
"""
request_cache_dict = get_cache(self.REQUEST_CACHE_NAME)
if request_cache_dict:
last_supported_date = request_cache_dict[
self.LAST_SUPPORTED_DATE_HEADER]
if last_supported_date != self.NO_LAST_SUPPORTED_DATE:
response[
self.
LAST_SUPPORTED_DATE_HEADER] = last_supported_date.isoformat(
)
latest_version = request_cache_dict[self.LATEST_VERSION_HEADER]
user_app_version = request_cache_dict[self.USER_APP_VERSION]
if (latest_version != self.NO_LATEST_VERSION
and parsed_version(user_app_version) <
parsed_version(latest_version)):
response[self.LATEST_VERSION_HEADER] = latest_version
return response
def bulk_cache_cohorts(course_key, users):
"""
Pre-fetches and caches the cohort assignments for the
given users, for later fast retrieval by get_cohort.
"""
# before populating the cache with another bulk set of data,
# remove previously cached entries to keep memory usage low.
clear_cache(COHORT_CACHE_NAMESPACE)
cache = get_cache(COHORT_CACHE_NAMESPACE)
if is_course_cohorted(course_key):
cohorts_by_user = {
membership.user: membership
for membership in CohortMembership.objects.filter(
user__in=users, course_id=course_key).select_related('user')
}
for user, membership in cohorts_by_user.iteritems():
cache[_cohort_cache_key(user.id,
course_key)] = membership.course_user_group
uncohorted_users = filter(lambda u: u not in cohorts_by_user, users)
else:
uncohorted_users = users
for user in uncohorted_users:
cache[_cohort_cache_key(user.id, course_key)] = None
def __enter__(self):
connection = transaction.get_connection(self.using)
cache = get_cache(OUTER_ATOMIC_CACHE_NAME)
# By default it is enabled.
enable = True
# If name is set it is only enabled if requested by calling enable_named_outer_atomic().
if self.name:
enable = cache.get(self.name, False)
if enable:
# TestCase setup nests tests in two atomics - one for the test class and one for the individual test.
# The outermost atomic starts a transaction - so does not have a savepoint.
# The inner atomic starts a savepoint around the test.
# So, for tests only, there should be exactly one savepoint_id and two atomic_for_testcase_calls.
# atomic_for_testcase_calls below is added in a monkey-patch for tests only.
if self.ALLOW_NESTED and (self.atomic_for_testcase_calls -
len(connection.savepoint_ids)) < 1:
raise transaction.TransactionManagementError(
'Cannot be inside an atomic block.')
# Otherwise, this shouldn't be nested in any atomic block.
if not self.ALLOW_NESTED and connection.in_atomic_block:
raise transaction.TransactionManagementError(
'Cannot be inside an atomic block.')
# This will set the transaction isolation level to READ COMMITTED for the next transaction.
if self.read_committed is True:
if connection.vendor == 'mysql':
cursor = connection.cursor()
cursor.execute(
"SET TRANSACTION ISOLATION LEVEL READ COMMITTED")
super(OuterAtomic, self).__enter__()
def get_template_request_context(request=None):
"""
Returns the template processing context to use for the current request,
or returns None if there is not a current request.
"""
if request is None:
request = get_current_request()
if request is None:
return None
request_cache_dict = get_cache('edxmako')
cache_key = "request_context"
if cache_key in request_cache_dict:
return request_cache_dict[cache_key]
context = RequestContext(request)
context['is_secure'] = request.is_secure()
context['site'] = safe_get_host(request)
request_cache_dict[cache_key] = context
return context
def set_event_transaction_id(new_id):
"""
Sets the event transaction id to a UUID object
generated from new_id.
new_id must be a parsable string version
of a UUID.
"""
get_cache('event_transaction')['id'] = UUID(new_id)
def create_new_event_transaction_id():
"""
Sets the event transaction id to a newly-
generated UUID.
"""
new_id = uuid4()
get_cache('event_transaction')['id'] = new_id
return new_id
def _initialize_cache(cls, course_key):
"""
Prefetches visible blocks for the given course and stores in the cache.
Returns a dictionary mapping hashes of these block records to the
block record objects.
"""
prefetched = {record.hashed: record for record in cls.objects.filter(course_id=course_key)}
get_cache(cls._CACHE_NAMESPACE)[cls._cache_key(course_key)] = prefetched
return prefetched
def prefetch(cls, course_id, users):
"""
Prefetches grades for the given users for the given course.
"""
get_cache(cls._CACHE_NAMESPACE)[cls._cache_key(course_id)] = {
grade.user_id: grade
for grade in cls.objects.filter(
user_id__in=[user.id for user in users], course_id=course_id)
}
def _initialize_cache(cls, course_key):
"""
Prefetches visible blocks for the given course and stores in the cache.
Returns a dictionary mapping hashes of these block records to the
block record objects.
"""
prefetched = {record.hashed: record for record in cls.objects.filter(course_id=course_key)}
get_cache(cls._CACHE_NAMESPACE)[cls._cache_key(course_key)] = prefetched
return prefetched
def prefetch(cls, course_id, users):
"""
Prefetches grades for the given users for the given course.
"""
get_cache(cls._CACHE_NAMESPACE)[cls._cache_key(course_id)] = {
grade.user_id: grade
for grade in
cls.objects.filter(user_id__in=[user.id for user in users], course_id=course_id)
}
def prefetch(cls, users):
roles_by_user = defaultdict(set)
get_cache(cls.CACHE_NAMESPACE)[cls.CACHE_KEY] = roles_by_user
for role in CourseAccessRole.objects.filter(user__in=users).select_related('user'):
roles_by_user[role.user.id].add(role)
users_without_roles = filter(lambda u: u.id not in roles_by_user, users)
for user in users_without_roles:
roles_by_user[user.id] = set()
def prefetch(cls, users):
roles_by_user = defaultdict(set)
get_cache(cls.CACHE_NAMESPACE)[cls.CACHE_KEY] = roles_by_user
for role in CourseAccessRole.objects.filter(user__in=users).select_related('user'):
roles_by_user[role.user.id].add(role)
users_without_roles = filter(lambda u: u.id not in roles_by_user, users)
for user in users_without_roles:
roles_by_user[user.id] = set()
def get_override(cls, user_id, usage_key):
prefetch_values = get_cache(cls._CACHE_NAMESPACE).get((user_id, str(usage_key.course_key)), None)
if prefetch_values is not None:
return prefetch_values.get(usage_key)
try:
return cls.objects.get(
grade__user_id=user_id,
grade__course_id=usage_key.course_key,
grade__usage_key=usage_key,
)
except PersistentSubsectionGradeOverride.DoesNotExist:
pass
def get_override(cls, user_id, usage_key):
prefetch_values = get_cache(cls._CACHE_NAMESPACE).get((user_id, str(usage_key.course_key)), None)
if prefetch_values is not None:
return prefetch_values.get(usage_key)
try:
return cls.objects.get(
grade__user_id=user_id,
grade__course_id=usage_key.course_key,
grade__usage_key=usage_key,
)
except PersistentSubsectionGradeOverride.DoesNotExist:
pass
def bulk_read(cls, user_id, course_key):
"""
Reads and returns all visible block records for the given user and course from
the cache. The cache is initialized with the visible blocks for this user and
course if no entry currently exists.
Arguments:
course_key: The course identifier for the desired records
"""
prefetched = get_cache(cls._CACHE_NAMESPACE).get(cls._cache_key(user_id, course_key), None)
if prefetched is None:
prefetched = cls._initialize_cache(user_id, course_key)
return prefetched
def _initialize_cache(cls, user_id, course_key):
"""
Prefetches visible blocks for the given user and course and stores in the cache.
Returns a dictionary mapping hashes of these block records to the
block record objects.
"""
grades_with_blocks = PersistentSubsectionGrade.objects.select_related('visible_blocks').filter(
user_id=user_id,
course_id=course_key,
)
prefetched = {grade.visible_blocks.hashed: grade.visible_blocks for grade in grades_with_blocks}
get_cache(cls._CACHE_NAMESPACE)[cls._cache_key(user_id, course_key)] = prefetched
return prefetched
def bulk_read(cls, user_id, course_key):
"""
Reads and returns all visible block records for the given user and course from
the cache. The cache is initialized with the visible blocks for this user and
course if no entry currently exists.
Arguments:
course_key: The course identifier for the desired records
"""
prefetched = get_cache(cls._CACHE_NAMESPACE).get(cls._cache_key(user_id, course_key), None)
if prefetched is None:
prefetched = cls._initialize_cache(user_id, course_key)
return prefetched
def _initialize_cache(cls, user_id, course_key):
"""
Prefetches visible blocks for the given user and course and stores in the cache.
Returns a dictionary mapping hashes of these block records to the
block record objects.
"""
grades_with_blocks = PersistentSubsectionGrade.objects.select_related('visible_blocks').filter(
user_id=user_id, # TODO: Edraak: Remove the `user_id` filter to fix OU-426. Check with edX.
# See `VisibleBlocks.bulk_create` for the related hack.
course_id=course_key,
)
prefetched = {grade.visible_blocks.hashed: grade.visible_blocks for grade in grades_with_blocks}
get_cache(cls._CACHE_NAMESPACE)[cls._cache_key(user_id, course_key)] = prefetched
return prefetched
def cached_get_or_create(cls, blocks):
prefetched = get_cache(cls._CACHE_NAMESPACE).get(cls._cache_key(blocks.course_key))
if prefetched is not None:
model = prefetched.get(blocks.hash_value)
if not model:
model = cls.objects.create(
hashed=blocks.hash_value, blocks_json=blocks.json_value, course_id=blocks.course_key,
)
cls._update_cache(blocks.course_key, [model])
else:
model, _ = cls.objects.get_or_create(
hashed=blocks.hash_value,
defaults={u'blocks_json': blocks.json_value, u'course_id': blocks.course_key},
)
return model
def cached_get_or_create(cls, blocks):
prefetched = get_cache(cls._CACHE_NAMESPACE).get(cls._cache_key(blocks.course_key))
if prefetched is not None:
model = prefetched.get(blocks.hash_value)
if not model:
model = cls.objects.create(
hashed=blocks.hash_value, blocks_json=blocks.json_value, course_id=blocks.course_key,
)
cls._update_cache(blocks.course_key, [model])
else:
model, _ = cls.objects.get_or_create(
hashed=blocks.hash_value,
defaults={u'blocks_json': blocks.json_value, u'course_id': blocks.course_key},
)
return model
def get_current_ccx(course_key):
"""
Return the ccx that is active for this course.
course_key is expected to be an instance of an opaque CourseKey, a
ValueError is raised if this expectation is not met.
"""
if not isinstance(course_key, CourseKey):
raise ValueError("get_current_ccx requires a CourseKey instance")
if not isinstance(course_key, CCXLocator):
return None
ccx_cache = get_cache('ccx')
if course_key not in ccx_cache:
ccx_cache[course_key] = CustomCourseForEdX.objects.get(pk=course_key.ccx)
return ccx_cache[course_key]
def prefetch(cls, course_id, users):
"""
Prefetches the value of the course tags for the specified users
for the specified course_id.
Args:
users: iterator of User objects
course_id: course identifier (CourseKey)
Returns:
course_tags: a dict of dicts,
where the primary key is the user's id
and the secondary key is the course tag's key
"""
course_tags = defaultdict(dict)
for tag in UserCourseTag.objects.filter(user__in=users, course_id=course_id).select_related('user'):
course_tags[tag.user.id][tag.key] = tag.value
get_cache(cls.CACHE_NAMESPACE)[cls._cache_key(course_id)] = course_tags
def _initialize_cache(cls, user_id, course_key):
"""
Prefetches visible blocks for the given user and course and stores in the cache.
Returns a dictionary mapping hashes of these block records to the
block record objects.
"""
grades_with_blocks = PersistentSubsectionGrade.objects.select_related(
'visible_blocks').filter(
user_id=user_id,
course_id=course_key,
)
prefetched = {
grade.visible_blocks.hashed: grade.visible_blocks
for grade in grades_with_blocks
}
get_cache(cls._CACHE_NAMESPACE)[cls._cache_key(
user_id, course_key)] = prefetched
return prefetched
def get_current_ccx(course_key):
"""
Return the ccx that is active for this course.
course_key is expected to be an instance of an opaque CourseKey, a
ValueError is raised if this expectation is not met.
"""
if not isinstance(course_key, CourseKey):
raise ValueError("get_current_ccx requires a CourseKey instance")
if not isinstance(course_key, CCXLocator):
return None
ccx_cache = get_cache('ccx')
if course_key not in ccx_cache:
ccx_cache[course_key] = CustomCourseForEdX.objects.get(pk=course_key.ccx)
return ccx_cache[course_key]
def prefetch(cls, course_id, users):
"""
Prefetches the value of the course tags for the specified users
for the specified course_id.
Args:
users: iterator of User objects
course_id: course identifier (CourseKey)
Returns:
course_tags: a dict of dicts,
where the primary key is the user's id
and the secondary key is the course tag's key
"""
course_tags = defaultdict(dict)
for tag in UserCourseTag.objects.filter(
user__in=users, course_id=course_id).select_related('user'):
course_tags[tag.user.id][tag.key] = tag.value
get_cache(cls.CACHE_NAMESPACE)[cls._cache_key(course_id)] = course_tags
def _get_version_info(self, request):
"""
Gets and Sets version related info in mem cache and request cache; and returns a dict of it.
It sets request cache data for last_supported_date and latest_version with memcached values if exists against
user app properties else computes the values for specific platform and sets it in both memcache (for next
server interaction from same app version/platform) and request cache
Returns:
dict: Containing app version info
"""
user_agent = request.META.get('HTTP_USER_AGENT')
if user_agent:
platform = self._get_platform(request, user_agent)
if platform:
request_cache_dict = get_cache(self.REQUEST_CACHE_NAME)
request_cache_dict[self.USER_APP_VERSION] = platform.version
last_supported_date_cache_key = self._get_cache_key_name(
self.LAST_SUPPORTED_DATE_HEADER, platform.version)
latest_version_cache_key = self._get_cache_key_name(
self.LATEST_VERSION_HEADER, platform.NAME)
cached_data = cache.get_many(
[last_supported_date_cache_key, latest_version_cache_key])
last_supported_date = cached_data.get(
last_supported_date_cache_key)
if not last_supported_date:
last_supported_date = self._get_last_supported_date(
platform.NAME, platform.version)
cache.set(last_supported_date_cache_key,
last_supported_date, self.CACHE_TIMEOUT)
request_cache_dict[
self.LAST_SUPPORTED_DATE_HEADER] = last_supported_date
latest_version = cached_data.get(latest_version_cache_key)
if not latest_version:
latest_version = self._get_latest_version(platform.NAME)
cache.set(latest_version_cache_key, latest_version,
self.CACHE_TIMEOUT)
request_cache_dict[self.LATEST_VERSION_HEADER] = latest_version
return request_cache_dict
def _get_overrides_for_ccx(ccx):
"""
Returns a dictionary mapping field name to overriden value for any
overrides set on this block for this CCX.
"""
overrides_cache = get_cache('ccx-overrides')
if ccx not in overrides_cache:
overrides = {}
query = CcxFieldOverride.objects.filter(ccx=ccx, )
for override in query:
block_overrides = overrides.setdefault(override.location, {})
block_overrides[override.field] = json.loads(override.value)
block_overrides[override.field + "_id"] = override.id
block_overrides[override.field + "_instance"] = override
overrides_cache[ccx] = overrides
return overrides_cache[ccx]
def enable_named_outer_atomic(*names):
"""
Enable outer_atomics with names.
Can be used either as a decorator or a context manager.
See docstring of outer_atomic for details.
Arguments:
names (variable-lenght argument list): Names of outer_atomics.
"""
if len(names) == 0:
raise ValueError("At least one name must be specified.")
cache = get_cache(OUTER_ATOMIC_CACHE_NAME)
for name in names:
cache[name] = True
yield
for name in names:
del cache[name]
def enable_named_outer_atomic(*names):
"""
Enable outer_atomics with names.
Can be used either as a decorator or a context manager.
See docstring of outer_atomic for details.
Arguments:
names (variable-lenght argument list): Names of outer_atomics.
"""
if len(names) == 0:
raise ValueError("At least one name must be specified.")
cache = get_cache(OUTER_ATOMIC_CACHE_NAME)
for name in names:
cache[name] = True
yield
for name in names:
del cache[name]
def read(cls, user_id, course_id):
"""
Reads a grade from database
Arguments:
user_id: The user associated with the desired grade
course_id: The id of the course associated with the desired grade
Raises PersistentCourseGrade.DoesNotExist if applicable
"""
try:
prefetched_grades = get_cache(cls._CACHE_NAMESPACE)[cls._cache_key(course_id)]
try:
return prefetched_grades[user_id]
except KeyError:
# user's grade is not in the prefetched list, so
# assume they have no grade
raise cls.DoesNotExist
except KeyError:
# grades were not prefetched for the course, so fetch it
return cls.objects.get(user_id=user_id, course_id=course_id)
def process_response(self, __, response):
"""
If request is from mobile native app, then add version related info to response headers.
Returns:
Http response: with additional headers;
1. EDX-APP-LATEST-VERSION; if user app version < latest available version
2. EDX-APP-VERSION-LAST-SUPPORTED-DATE; if user app version < min supported version and
timestamp < expiry of that version
"""
request_cache_dict = get_cache(self.REQUEST_CACHE_NAME)
if request_cache_dict:
last_supported_date = request_cache_dict[self.LAST_SUPPORTED_DATE_HEADER]
if last_supported_date != self.NO_LAST_SUPPORTED_DATE:
response[self.LAST_SUPPORTED_DATE_HEADER] = last_supported_date.isoformat()
latest_version = request_cache_dict[self.LATEST_VERSION_HEADER]
user_app_version = request_cache_dict[self.USER_APP_VERSION]
if (latest_version != self.NO_LATEST_VERSION and
parsed_version(user_app_version) < parsed_version(latest_version)):
response[self.LATEST_VERSION_HEADER] = latest_version
return response
def read(cls, user_id, course_id):
"""
Reads a grade from database
Arguments:
user_id: The user associated with the desired grade
course_id: The id of the course associated with the desired grade
Raises PersistentCourseGrade.DoesNotExist if applicable
"""
try:
prefetched_grades = get_cache(cls._CACHE_NAMESPACE)[cls._cache_key(course_id)]
try:
return prefetched_grades[user_id]
except KeyError:
# user's grade is not in the prefetched list, so
# assume they have no grade
raise cls.DoesNotExist
except KeyError:
# grades were not prefetched for the course, so fetch it
return cls.objects.get(user_id=user_id, course_id=course_id)
def _get_overrides_for_ccx(ccx):
"""
Returns a dictionary mapping field name to overriden value for any
overrides set on this block for this CCX.
"""
overrides_cache = get_cache('ccx-overrides')
if ccx not in overrides_cache:
overrides = {}
query = CcxFieldOverride.objects.filter(
ccx=ccx,
)
for override in query:
block_overrides = overrides.setdefault(override.location, {})
block_overrides[override.field] = json.loads(override.value)
block_overrides[override.field + "_id"] = override.id
block_overrides[override.field + "_instance"] = override
overrides_cache[ccx] = overrides
return overrides_cache[ccx]
def _get_version_info(self, request):
"""
Gets and Sets version related info in mem cache and request cache; and returns a dict of it.
It sets request cache data for last_supported_date and latest_version with memcached values if exists against
user app properties else computes the values for specific platform and sets it in both memcache (for next
server interaction from same app version/platform) and request cache
Returns:
dict: Containing app version info
"""
user_agent = request.META.get('HTTP_USER_AGENT')
if user_agent:
platform = self._get_platform(request, user_agent)
if platform:
request_cache_dict = get_cache(self.REQUEST_CACHE_NAME)
request_cache_dict[self.USER_APP_VERSION] = platform.version
last_supported_date_cache_key = self._get_cache_key_name(
self.LAST_SUPPORTED_DATE_HEADER,
platform.version
)
latest_version_cache_key = self._get_cache_key_name(self.LATEST_VERSION_HEADER, platform.NAME)
cached_data = cache.get_many([last_supported_date_cache_key, latest_version_cache_key])
last_supported_date = cached_data.get(last_supported_date_cache_key)
if not last_supported_date:
last_supported_date = self._get_last_supported_date(platform.NAME, platform.version)
cache.set(last_supported_date_cache_key, last_supported_date, self.CACHE_TIMEOUT)
request_cache_dict[self.LAST_SUPPORTED_DATE_HEADER] = last_supported_date
latest_version = cached_data.get(latest_version_cache_key)
if not latest_version:
latest_version = self._get_latest_version(platform.NAME)
cache.set(latest_version_cache_key, latest_version, self.CACHE_TIMEOUT)
request_cache_dict[self.LATEST_VERSION_HEADER] = latest_version
return request_cache_dict
def cached_get_or_create(cls, user_id, blocks):
"""
Given a ``user_id`` and a ``BlockRecordList`` object, attempts to
fetch the related VisibleBlocks model from the request cache. This
will create and save a new ``VisibleBlocks`` record if no record
exists corresponding to the hash_value of ``blocks``.
"""
prefetched = get_cache(cls._CACHE_NAMESPACE).get(cls._cache_key(user_id, blocks.course_key))
if prefetched is not None:
model = prefetched.get(blocks.hash_value)
if not model:
# We still have to do a get_or_create, because
# another user may have had this block hash created,
# even if the user we checked the cache for hasn't yet.
model, _ = cls.objects.get_or_create(
hashed=blocks.hash_value, blocks_json=blocks.json_value, course_id=blocks.course_key,
)
cls._update_cache(user_id, blocks.course_key, [model])
else:
model, _ = cls.objects.get_or_create(
hashed=blocks.hash_value,
defaults={u'blocks_json': blocks.json_value, u'course_id': blocks.course_key},
)
return model
def bulk_cache_cohorts(course_key, users):
"""
Pre-fetches and caches the cohort assignments for the
given users, for later fast retrieval by get_cohort.
"""
# before populating the cache with another bulk set of data,
# remove previously cached entries to keep memory usage low.
clear_cache(COHORT_CACHE_NAMESPACE)
cache = get_cache(COHORT_CACHE_NAMESPACE)
if is_course_cohorted(course_key):
cohorts_by_user = {
membership.user: membership
for membership in
CohortMembership.objects.filter(user__in=users, course_id=course_key).select_related('user')
}
for user, membership in cohorts_by_user.iteritems():
cache[_cohort_cache_key(user.id, course_key)] = membership.course_user_group
uncohorted_users = filter(lambda u: u not in cohorts_by_user, users)
else:
uncohorted_users = users
for user in uncohorted_users:
cache[_cohort_cache_key(user.id, course_key)] = None
def get_user_roles(cls, user):
return get_cache(cls.CACHE_NAMESPACE)[cls.CACHE_KEY][user.id]
def _cache(self):
"""
Namespaced request cache for tracking memory usage.
"""
return get_cache(name='monitoring_memory')
def is_prefetched(cls, course_id):
return cls._cache_key(course_id) in get_cache(cls.CACHE_NAMESPACE)
def prefetch(cls, user_id, course_key):
get_cache(cls._CACHE_NAMESPACE)[(user_id, str(course_key))] = {
override.grade.usage_key: override
for override in
cls.objects.filter(grade__user_id=user_id, grade__course_id=course_key)
}
def _update_cache(cls, course_id, user_id, grade):
course_cache = get_cache(cls._CACHE_NAMESPACE).get(cls._cache_key(course_id))
if course_cache is not None:
course_cache[user_id] = grade
def _get_metrics_cache(cls):
"""
Get a reference to the part of the request cache wherein we store New
Relic custom metrics related to the current request.
"""
return get_cache(name=REQUEST_CACHE_KEY)
def _cache(self):
"""
Namespaced request cache for tracking memory usage.
"""
return get_cache(name='monitoring_memory')
def _get_metrics_cache(cls):
"""
Get a reference to the part of the request cache wherein we store New
Relic custom metrics related to the current request.
"""
return get_cache(name=REQUEST_CACHE_KEY)
def get_cohort(user, course_key, assign=True, use_cached=False):
"""
Returns the user's cohort for the specified course.
The cohort for the user is cached for the duration of a request. Pass
use_cached=True to use the cached value instead of fetching from the
database.
Arguments:
user: a Django User object.
course_key: CourseKey
assign (bool): if False then we don't assign a group to user
use_cached (bool): Whether to use the cached value or fetch from database.
Returns:
A CourseUserGroup object if the course is cohorted and the User has a
cohort, else None.
Raises:
ValueError if the CourseKey doesn't exist.
"""
cache = get_cache(COHORT_CACHE_NAMESPACE)
cache_key = _cohort_cache_key(user.id, course_key)
if use_cached and cache_key in cache:
return cache[cache_key]
cache.pop(cache_key, None)
# First check whether the course is cohorted (users shouldn't be in a cohort
# in non-cohorted courses, but settings can change after course starts)
if not is_course_cohorted(course_key):
return cache.setdefault(cache_key, None)
# If course is cohorted, check if the user already has a cohort.
try:
membership = CohortMembership.objects.get(
course_id=course_key,
user_id=user.id,
)
return cache.setdefault(cache_key, membership.course_user_group)
except CohortMembership.DoesNotExist:
# Didn't find the group. If we do not want to assign, return here.
if not assign:
# Do not cache the cohort here, because in the next call assign
# may be True, and we will have to assign the user a cohort.
return None
# Otherwise assign the user a cohort.
try:
with transaction.atomic():
# If learner has been pre-registered in a cohort, get that cohort. Otherwise assign to a random cohort.
course_user_group = None
for assignment in UnregisteredLearnerCohortAssignments.objects.filter(email=user.email, course_id=course_key):
course_user_group = assignment.course_user_group
unregistered_learner = assignment
if course_user_group:
unregistered_learner.delete()
else:
course_user_group = get_random_cohort(course_key)
membership = CohortMembership.objects.create(
user=user,
course_user_group=course_user_group,
)
return cache.setdefault(cache_key, membership.course_user_group)
except IntegrityError as integrity_error:
# An IntegrityError is raised when multiple workers attempt to
# create the same row in one of the cohort model entries:
# CourseCohort, CohortMembership.
log.info(
"HANDLING_INTEGRITY_ERROR: IntegrityError encountered for course '%s' and user '%s': %s",
course_key, user.id, unicode(integrity_error)
)
return get_cohort(user, course_key, assign, use_cached)
def get_user_roles(cls, user):
return get_cache(cls.CACHE_NAMESPACE)[cls.CACHE_KEY][user.id]
def _update_cache(cls, course_id, user_id, grade):
course_cache = get_cache(cls._CACHE_NAMESPACE).get(
cls._cache_key(course_id))
if course_cache is not None:
course_cache[user_id] = grade
def get_course_tag(cls, user_id, course_id, key):
return get_cache(cls.CACHE_NAMESPACE)[cls._cache_key(course_id)][user_id][key]
def prefetch(cls, user_id, course_key):
get_cache(cls._CACHE_NAMESPACE)[(user_id, str(course_key))] = {
override.grade.usage_key: override
for override in cls.objects.filter(grade__user_id=user_id,
grade__course_id=course_key)
}