Percentage-based Enablement for Feature Toggle (aws#1952)

* Percentage-based Enablement for Feature Toggle

* Update Feature Toggle to accept stage, account_id and region during instanciation

* remove unnecessary uses of dict.get method

* Refactor feature toggle methods

* Update test names

* black reformat

* Update FeatureToggle to require stage, region and account_id to instanciate

* Update log message

* Implement calculating account percentile based on hash of account_id and feature_name

* Refactor _is_feature_enabled_for_region_config

* Refactor dialup logic into its own classes

* Add comments for dialup classes

* Rename NeverEnabledDialup to DisabledDialup

Author: hawflau

samtranslator/feature_toggle/dialup.py

@@ -0,0 +1,74 @@
+import hashlib
+
+
+class BaseDialup(object):
+    """BaseDialup class to provide an interface for all dialup classes"""
+
+    def __init__(self, region_config, **kwargs):
+        self.region_config = region_config
+
+    def is_enabled(self):
+        """
+        Returns a bool on whether this dialup is enabled or not
+        """
+        raise NotImplementedError
+
+    def __str__(self):
+        return self.__class__.__name__
+
+
+class DisabledDialup(BaseDialup):
+    """
+    A dialup that is never enabled
+    """
+
+    def __init__(self, region_config, **kwargs):
+        super(DisabledDialup, self).__init__(region_config)
+
+    def is_enabled(self):
+        return False
+
+
+class ToggleDialup(BaseDialup):
+    """
+    A simple toggle Dialup
+    Example of region_config: { "type": "toggle", "enabled": True }
+    """
+
+    def __init__(self, region_config, **kwargs):
+        super(ToggleDialup, self).__init__(region_config)
+        self.region_config = region_config
+
+    def is_enabled(self):
+        return self.region_config.get("enabled", False)
+
+
+class SimpleAccountPercentileDialup(BaseDialup):
+    """
+    Simple account percentile dialup, enabling X% of
+    Example of region_config: { "type": "account-percentile", "enabled-%": 20 }
+    """
+
+    def __init__(self, region_config, account_id, feature_name, **kwargs):
+        super(SimpleAccountPercentileDialup, self).__init__(region_config)
+        self.account_id = account_id
+        self.feature_name = feature_name
+
+    def _get_account_percentile(self):
+        """
+        Get account percentile based on sha256 hash of account ID and feature_name
+
+        :returns: integer n, where 0 <= n < 100
+        """
+        m = hashlib.sha256()
+        m.update(self.account_id.encode())
+        m.update(self.feature_name.encode())
+        return int(m.hexdigest(), 16) % 100
+
+    def is_enabled(self):
+        """
+        Enable when account_percentile falls within target_percentile
+        Meaning only (target_percentile)% of accounts will be enabled
+        """
+        target_percentile = self.region_config.get("enabled-%", 0)
+        return self._get_account_percentile() < target_percentile

samtranslator/feature_toggle/feature_toggle.py

@@ -3,8 +3,14 @@
 import json
 import boto3
 import logging
+import hashlib
 
 from botocore.config import Config
+from samtranslator.feature_toggle.dialup import (
+    DisabledDialup,
+    ToggleDialup,
+    SimpleAccountPercentileDialup,
+)
 
 my_path = os.path.dirname(os.path.abspath(__file__))
 sys.path.insert(0, my_path + "/..")
@@ -18,50 +24,69 @@ class FeatureToggle:
     SAM is executing or not.
     """
 
-    def __init__(self, config_provider):
+    DIALUP_RESOLVER = {
+        "toggle": ToggleDialup,
+        "account-percentile": SimpleAccountPercentileDialup,
+    }
+
+    def __init__(self, config_provider, stage, account_id, region):
         self.feature_config = config_provider.config
+        self.stage = stage
+        self.account_id = account_id
+        self.region = region
 
-    def is_enabled_for_stage_in_region(self, feature_name, stage, region="default"):
+    def _get_dialup(self, region_config, feature_name):
         """
-        To check if feature is available for a particular stage or not.
-        :param feature_name: name of feature
-        :param stage: stage where SAM is running
-        :param region: region in which SAM is running
-        :return:
+        get the right dialup instance
+        if no dialup type is provided or the specified dialup is not supported,
+        an instance of DisabledDialup will be returned
+
+        :param region_config: region config
+        :param feature_name: feature_name
+        :return: an instance of
         """
-        if feature_name not in self.feature_config:
-            LOG.warning("Feature '{}' not available in Feature Toggle Config.".format(feature_name))
-            return False
-        stage_config = self.feature_config.get(feature_name, {}).get(stage, {})
-        if not stage_config:
-            LOG.info("Stage '{}' not enabled for Feature '{}'.".format(stage, feature_name))
-            return False
-        region_config = stage_config.get(region, {}) if region in stage_config else stage_config.get("default", {})
-        is_enabled = region_config.get("enabled", False)
-        LOG.info("Feature '{}' is enabled: '{}'".format(feature_name, is_enabled))
-        return is_enabled
+        dialup_type = region_config.get("type")
+        if dialup_type in FeatureToggle.DIALUP_RESOLVER:
+            return FeatureToggle.DIALUP_RESOLVER[dialup_type](
+                region_config, account_id=self.account_id, feature_name=feature_name
+            )
+        LOG.warning("Dialup type '{}' is None or is not supported.".format(dialup_type))
+        return DisabledDialup(region_config)
 
-    def is_enabled_for_account_in_region(self, feature_name, stage, account_id, region="default"):
+    def is_enabled(self, feature_name):
         """
-        To check if feature is available for a particular account or not.
+        To check if feature is available
+
         :param feature_name: name of feature
-        :param stage: stage where SAM is running
-        :param account_id: account_id who is executing SAM template
-        :param region: region in which SAM is running
-        :return:
         """
         if feature_name not in self.feature_config:
             LOG.warning("Feature '{}' not available in Feature Toggle Config.".format(feature_name))
             return False
+
+        stage = self.stage
+        region = self.region
+        account_id = self.account_id
+        if not stage or not region or not account_id:
+            LOG.warning(
+                "One or more of stage, region and account_id is not set. Feature '{}' not enabled.".format(feature_name)
+            )
+            return False
+
         stage_config = self.feature_config.get(feature_name, {}).get(stage, {})
         if not stage_config:
             LOG.info("Stage '{}' not enabled for Feature '{}'.".format(stage, feature_name))
             return False
-        account_config = stage_config.get(account_id) if account_id in stage_config else stage_config.get("default", {})
-        region_config = (
-            account_config.get(region, {}) if region in account_config else account_config.get("default", {})
-        )
-        is_enabled = region_config.get("enabled", False)
+
+        if account_id in stage_config:
+            account_config = stage_config[account_id]
+            region_config = account_config[region] if region in account_config else account_config.get("default", {})
+        else:
+            region_config = stage_config[region] if region in stage_config else stage_config.get("default", {})
+
+        dialup = self._get_dialup(region_config, feature_name=feature_name)
+        LOG.info("Using Dialip {}".format(dialup))
+        is_enabled = dialup.is_enabled()
+
         LOG.info("Feature '{}' is enabled: '{}'".format(feature_name, is_enabled))
         return is_enabled
 

samtranslator/translator/translator.py

@@ -92,7 +92,11 @@ def translate(self, sam_template, parameter_values, feature_toggle=None):
         :returns: a copy of the template with SAM resources replaced with the corresponding CloudFormation, which may \
                 be dumped into a valid CloudFormation JSON or YAML template
         """
-        self.feature_toggle = feature_toggle if feature_toggle else FeatureToggle(FeatureToggleDefaultConfigProvider())
+        self.feature_toggle = (
+            feature_toggle
+            if feature_toggle
+            else FeatureToggle(FeatureToggleDefaultConfigProvider(), stage=None, account_id=None, region=None)
+        )
         self.function_names = dict()
         self.redeploy_restapi_parameters = dict()
         sam_parameter_values = SamParameterValues(parameter_values)

tests/feature_toggle/input/feature_toggle_config.json

@@ -2,13 +2,20 @@
     "__note__": "This is a dummy config for local testing. Any change here need to be migrated to SAM service.",
     "feature-1": {
         "beta": {
-            "us-west-2": {"enabled": true},
-            "default": {"enabled": false},
-            "123456789123": {"us-west-2": {"enabled": true}, "default": {"enabled": false}}
+            "us-west-2": {"type": "toggle", "enabled": true},
+            "us-east-1": {"type": "account-percentile", "enabled-%": 10},
+            "default": {"type": "toggle", "enabled": false},
+            "123456789123": {
+                "us-west-2": {"type": "toggle", "enabled": true},
+                "default": {"type": "toggle", "enabled": false}
+            }
         },
         "gamma": {
-            "default": {"enabled": false},
-            "123456789123": {"us-east-1": {"enabled": false}, "default": {"enabled": false}}
+            "default": {"type": "toggle", "enabled": false},
+            "123456789123": {
+                "us-east-1": {"type": "toggle", "enabled": false},
+                "default": {"type": "toggle", "enabled": false}
+            }
         },
         "prod": {"default": {"enabled": false}}
     }

tests/feature_toggle/test_dialup.py

@@ -0,0 +1,65 @@
+from unittest import TestCase
+
+from parameterized import parameterized, param
+from samtranslator.feature_toggle.dialup import *
+
+
+class TestBaseDialup(TestCase):
+    def test___str__(self):
+        region_config = {}
+        dialup = BaseDialup(region_config)
+        self.assertEqual(str(dialup), "BaseDialup")
+
+
+class TestDisabledDialup(TestCase):
+    def test_is_enabled(self):
+        region_config = {}
+        dialup = DisabledDialup(region_config)
+        self.assertFalse(dialup.is_enabled())
+
+
+class TestToggleDialUp(TestCase):
+    @parameterized.expand(
+        [
+            param({"type": "toggle", "enabled": True}, True),
+            param({"type": "toggle", "enabled": False}, False),
+            param({"type": "toggle"}, False),  # missing "enabled" key
+        ]
+    )
+    def test_is_enabled(self, region_config, expected):
+        dialup = ToggleDialup(region_config)
+        self.assertEqual(dialup.is_enabled(), expected)
+
+
+class TestSimpleAccountPercentileDialup(TestCase):
+    @parameterized.expand(
+        [
+            param({"type": "account-percentile", "enabled-%": 10}, "feature-1", "123456789100", True),
+            param({"type": "account-percentile", "enabled-%": 10}, "feautre-1", "123456789123", False),
+            param({"type": "account-percentile", "enabled": True}, "feature-1", "123456789100", False),
+        ]
+    )
+    def test_is_enabled(self, region_config, feature_name, account_id, expected):
+        dialup = SimpleAccountPercentileDialup(
+            region_config=region_config,
+            account_id=account_id,
+            feature_name=feature_name,
+        )
+        self.assertEqual(dialup.is_enabled(), expected)
+
+    @parameterized.expand(
+        [
+            param("feature-1", "123456789123"),
+            param("feature-2", "000000000000"),
+            param("feature-3", "432187654321"),
+            param("feature-4", "111222333444"),
+        ]
+    )
+    def test__get_account_percentile(self, account_id, feature_name):
+        region_config = {"type": "account-percentile", "enabled-%": 10}
+        dialup = SimpleAccountPercentileDialup(
+            region_config=region_config,
+            account_id=account_id,
+            feature_name=feature_name,
+        )
+        self.assertTrue(0 <= dialup._get_account_percentile() < 100)