Implement allow list (#7)

* implement allowlist

* fix type error

Author: ploomiz

eppo_client/client.py

@@ -1,3 +1,4 @@
+import hashlib
 from typing import Optional
 from eppo_client.configuration_requestor import (
     ExperimentConfigurationDto,
@@ -37,6 +38,9 @@ def assign(self, subject: str, experiment_key: str) -> Optional[str]:
             )
         ):
             return None
+        override = self._get_subject_variation_override(experiment_config, subject)
+        if override:
+            return override
         shard = get_shard(
             "assignment-{}-{}".format(subject, experiment_key),
             experiment_config.subject_shards,
@@ -56,6 +60,14 @@ def _shutdown(self):
         """
         self.__poller.stop()
 
+    def _get_subject_variation_override(
+        self, experiment_config: ExperimentConfigurationDto, subject: str
+    ) -> Optional[str]:
+        subject_hash = hashlib.md5(subject.encode("utf-8")).hexdigest()
+        if subject_hash in experiment_config.overrides:
+            return experiment_config.overrides[subject_hash]
+        return None
+
     def _is_in_experiment_sample(
         self,
         subject: str,

eppo_client/configuration_requestor.py

@@ -20,6 +20,7 @@ class ExperimentConfigurationDto(SdkBaseModel):
     enabled: bool
     variations: List[VariationDto]
     name: Optional[str]
+    overrides: Dict[str, str] = {}
 
 
 RAC_ENDPOINT = "/randomized_assignment/config"

test/client_test.py

@@ -75,11 +75,28 @@ def test_assign_subject_not_in_sample(mock_config_requestor):
             VariationDto(name="control", shardRange=ShardRange(start=0, end=100))
         ],
         name="recommendation_algo",
+        overrides=dict(),
     )
     client = EppoClient(config_requestor=mock_config_requestor)
     assert client.assign("user-1", "experiment-key-1") is None
 
 
+@patch("eppo_client.configuration_requestor.ExperimentConfigurationRequestor")
+def test_with_subject_in_overrides(mock_config_requestor):
+    mock_config_requestor.get_configuration.return_value = ExperimentConfigurationDto(
+        subjectShards=10000,
+        percentExposure=100,
+        enabled=True,
+        variations=[
+            VariationDto(name="control", shardRange=ShardRange(start=0, end=100))
+        ],
+        name="recommendation_algo",
+        overrides={"d6d7705392bc7af633328bea8c4c6904": "override-variation"},
+    )
+    client = EppoClient(config_requestor=mock_config_requestor)
+    assert client.assign("user-1", "experiment-key-1") == "override-variation"
+
+
 @pytest.mark.parametrize("test_case", test_data)
 def test_assign_subject_in_sample(test_case):
     print("---- Test case for {} Experiment".format(test_case["experiment"]))