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add waffle_flag custom metric (#24244)

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If setting ENABLE_WAFFLE_FLAG_METRIC is True, a custom
metric will be added with the values of all WaffleFlag
and CourseWaffleFlags seen during the transaction.

Metric flag values could be False, True, or Both.
The value Both would mean that the flag had both
a True and False value at different times through
the transaction. This is most likely due to having a
check_before_waffle_callback, as is the case with
CourseWaffleFlag.

Example metric value:

    "{'another.course.flag': 'False', 'some.flag': 'False', 'some.course.flag': 'Both'}"

Warning: NewRelic does not recommend large custom
metric values due to the potential performance
impact on the agent, so you may just want to
enable when researching usage of a particular flag.
Metric values longer than 255 are truncated.

TODO: A how_to can be added later if we find this
useful, including helpful querying tips.

ARCHBOM-132
This commit is contained in:
Robert Raposa
2020-06-18 12:21:57 -04:00
committed by GitHub
parent 7e459c7228
commit a1572dafce
2 changed files with 89 additions and 5 deletions
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54
openedx/core/djangoapps/waffle_utils/__init__.py
View File

@@ -67,6 +67,8 @@ from contextlib import contextmanager
import crum
import six
from django.conf import settings
from edx_django_utils.monitoring import set_custom_metric
from opaque_keys.edx.keys import CourseKey
from waffle import flag_is_active, switch_is_active
@@ -291,8 +293,60 @@ class WaffleFlagNamespace(six.with_metaclass(ABCMeta, WaffleNamespace)):
return bool(flag_undefined_default)
self._cached_flags[namespaced_flag_name] = value
self._set_waffle_flag_metric(namespaced_flag_name, value)
return value
def _set_waffle_flag_metric(self, name, value):
"""
If ENABLE_WAFFLE_FLAG_METRIC is True, adds name/value to cached values
and sets metric if the value changed.
Metric flag values could be False, True, or Both. The value Both would
mean that the flag had both a True and False value at different times
through the transaction. This is most likely due to having a
check_before_waffle_callback, as is the case with CourseWaffleFlag.
Example metric value::
"{'another.course.flag': 'False', 'some.flag': 'False', 'some.course.flag': 'Both'}"
Warning: NewRelic does not recommend large custom metric values due to
the potential performance impact on the agent, so you may just want to
enable when researching usage of a particular flag. Metric values longer
than 255 are truncated.
"""
is_waffle_flag_metric_enabled = getattr(settings, _ENABLE_WAFFLE_FLAG_METRIC, False)
if not is_waffle_flag_metric_enabled:
return
flag_metric_data = self._get_request_cache().setdefault('flag_metric', {})
is_value_change = False
if name not in flag_metric_data:
flag_metric_data[name] = str(value)
is_value_change = True
else:
if flag_metric_data[name] != str(value):
flag_metric_data[name] = 'Both'
is_value_change = True
if is_value_change:
set_custom_metric('waffle_flags', str(flag_metric_data))
# .. toggle_name: ENABLE_WAFFLE_FLAG_METRIC
# .. toggle_implementation: DjangoSetting
# .. toggle_default: False
# .. toggle_description: Set to True to enable a custom metric with waffle flag values (True, False, Both).
# .. toggle_category: monitoring
# .. toggle_use_cases: opt_out
# .. toggle_creation_date: 2020-06-17
# .. toggle_expiration_date: None
# .. toggle_tickets: None
# .. toggle_status: supported
# .. toggle_warnings: Metric of flags could be large and heavier than typical metrics.
_ENABLE_WAFFLE_FLAG_METRIC = 'ENABLE_WAFFLE_FLAG_METRIC'
class WaffleFlag(object):
"""

40
openedx/core/djangoapps/waffle_utils/tests/test_init.py
View File

@@ -6,8 +6,9 @@ import crum
import ddt
from django.test import TestCase
from django.test.client import RequestFactory
from django.test.utils import override_settings
from edx_django_utils.cache import RequestCache
from mock import patch
from mock import call, patch
from opaque_keys.edx.keys import CourseKey
from waffle.testutils import override_flag
@@ -37,13 +38,15 @@ class TestCourseWaffleFlag(TestCase):
crum.set_current_request(request)
RequestCache.clear_all_namespaces()
@override_settings(ENABLE_WAFFLE_FLAG_METRIC=True)
@patch('openedx.core.djangoapps.waffle_utils.set_custom_metric')
@ddt.data(
{'course_override': WaffleFlagCourseOverrideModel.ALL_CHOICES.on, 'waffle_enabled': False, 'result': True},
{'course_override': WaffleFlagCourseOverrideModel.ALL_CHOICES.off, 'waffle_enabled': True, 'result': False},
{'course_override': WaffleFlagCourseOverrideModel.ALL_CHOICES.unset, 'waffle_enabled': True, 'result': True},
{'course_override': WaffleFlagCourseOverrideModel.ALL_CHOICES.unset, 'waffle_enabled': False, 'result': False},
)
def test_course_waffle_flag(self, data):
def test_course_waffle_flag(self, data, mock_set_custom_metric):
"""
Tests various combinations of a flag being set in waffle and overridden
for a course.
@@ -59,22 +62,32 @@ class TestCourseWaffleFlag(TestCase):
self.TEST_COURSE_KEY
)
self._assert_waffle_flag_metric(mock_set_custom_metric, expected_flag_value=str(data['result']))
mock_set_custom_metric.reset_mock()
# check flag for a second course
if data['course_override'] == WaffleFlagCourseOverrideModel.ALL_CHOICES.unset:
# When course override wasn't set for the first course, the second course will get the same
# cached value from waffle.
self.assertEqual(self.TEST_COURSE_FLAG.is_enabled(self.TEST_COURSE_2_KEY), data['waffle_enabled'])
second_value = data['waffle_enabled']
self.assertEqual(self.TEST_COURSE_FLAG.is_enabled(self.TEST_COURSE_2_KEY), second_value)
else:
# When course override was set for the first course, it should not apply to the second
# course which should get the default value of False.
self.assertEqual(self.TEST_COURSE_FLAG.is_enabled(self.TEST_COURSE_2_KEY), False)
second_value = False
self.assertEqual(self.TEST_COURSE_FLAG.is_enabled(self.TEST_COURSE_2_KEY), second_value)
expected_flag_value = None if second_value == data['result'] else 'Both'
self._assert_waffle_flag_metric(mock_set_custom_metric, expected_flag_value=expected_flag_value)
@override_settings(ENABLE_WAFFLE_FLAG_METRIC=True)
@patch('openedx.core.djangoapps.waffle_utils.set_custom_metric')
@ddt.data(
{'flag_undefined_default': None, 'result': False},
{'flag_undefined_default': False, 'result': False},
{'flag_undefined_default': True, 'result': True},
)
def test_undefined_waffle_flag(self, data):
def test_undefined_waffle_flag(self, data, mock_set_custom_metric):
"""
Test flag with various defaults provided for undefined waffle flags.
"""
@@ -98,6 +111,8 @@ class TestCourseWaffleFlag(TestCase):
self.TEST_COURSE_KEY
)
self._assert_waffle_flag_metric(mock_set_custom_metric, expected_flag_value=str(data['result']))
@ddt.data(
{'flag_undefined_default': None, 'result': False},
{'flag_undefined_default': False, 'result': False},
@@ -115,6 +130,21 @@ class TestCourseWaffleFlag(TestCase):
)
self.assertEqual(test_course_flag.is_enabled(self.TEST_COURSE_KEY), data['result'])
@patch('openedx.core.djangoapps.waffle_utils.set_custom_metric')
def test_waffle_flag_metric_disabled(self, mock_set_custom_metric):
test_course_flag = CourseWaffleFlag(self.TEST_NAMESPACE, self.FLAG_NAME)
test_course_flag.is_enabled(self.TEST_COURSE_KEY)
self.assertEqual(mock_set_custom_metric.call_count, 0)
def _assert_waffle_flag_metric(self, mock_set_custom_metric, expected_flag_value=None):
if expected_flag_value:
expected_metric_value = str({self.NAMESPACED_FLAG_NAME: expected_flag_value})
expected_calls = [call('waffle_flags', expected_metric_value)]
mock_set_custom_metric.assert_has_calls(expected_calls)
self.assertEqual(mock_set_custom_metric.call_count, 1)
else:
self.assertEqual(mock_set_custom_metric.call_count, 0)
class TestWaffleSwitch(TestCase):
"""