fix: variants will now distribute correctly when used with a gradual rollout strategy (#282)

Author: sighphyre

UnleashClient/constants.py

@@ -6,7 +6,7 @@
 REQUEST_TIMEOUT = 30
 REQUEST_RETRIES = 3
 METRIC_LAST_SENT_TIME = "mlst"
-CLIENT_SPEC_VERSION = "4.5.0"
+CLIENT_SPEC_VERSION = "5.0.2"
 
 # =Unleash=
 APPLICATION_HEADERS = {

UnleashClient/utils.py

@@ -40,9 +40,13 @@ def increment(self, key):
 
 
 def normalized_hash(
-    identifier: str, activation_group: str, normalizer: int = 100
+    identifier: str, activation_group: str, normalizer: int = 100, seed: int = 0
 ) -> int:
-    return mmh3.hash(f"{activation_group}:{identifier}", signed=False) % normalizer + 1
+    return (
+        mmh3.hash(f"{activation_group}:{identifier}", signed=False, seed=seed)
+        % normalizer
+        + 1
+    )
 
 
 def get_identifier(context_key_name: str, context: dict) -> Any:

UnleashClient/variants/Variants.py

@@ -6,6 +6,8 @@
 from UnleashClient import utils
 from UnleashClient.constants import DISABLED_VARIATION
 
+VARIANT_HASH_SEED = 86028157
+
 
 class Variants:
     def __init__(
@@ -103,6 +105,7 @@ def get_variant(self, context: dict, flag_status: Optional[bool] = None) -> dict
                 self._get_seed(context, stickiness_selector),
                 self.group_id,
                 total_weight,
+                seed=VARIANT_HASH_SEED,
             )
             counter = 0
             for variation in self.variants:

tests/unit_tests/strategies/test_strategy_variants.py

@@ -36,8 +36,8 @@ def test_flexiblerollout_satisfies_constraints_returns_variant(strategy):
     assert result.enabled
     assert result.variant == {
         "enabled": True,
-        "name": "VarB",
-        "payload": {"type": "string", "value": "Test 2"},
+        "name": "VarC",
+        "payload": {"type": "string", "value": "Test 3"},
     }
 
 

tests/unit_tests/test_features.py

@@ -107,12 +107,12 @@ def test_select_variation_novariation(test_feature):
 def test_select_variation_variation(test_feature_variants):
     selected_variant = test_feature_variants.get_variant({"userId": "2"})
     assert selected_variant["enabled"]
-    assert selected_variant["name"] == "VarB"
+    assert selected_variant["name"] == "VarC"
 
 
 def test_variant_metrics_are_reset(test_feature_variants):
     test_feature_variants.get_variant({"userId": "2"})
-    assert test_feature_variants.variant_counts["VarB"] == 1
+    assert test_feature_variants.variant_counts["VarC"] == 1
 
     test_feature_variants.reset_stats()
     assert not test_feature_variants.variant_counts
@@ -121,7 +121,7 @@ def test_variant_metrics_are_reset(test_feature_variants):
 def test_variant_metrics_with_existing_variant(test_feature_variants):
     for iteration in range(1, 7):
         test_feature_variants.get_variant({"userId": "2"})
-        assert test_feature_variants.variant_counts["VarB"] == iteration
+        assert test_feature_variants.variant_counts["VarC"] == iteration
 
 
 def test_variant_metrics_with_disabled_feature(test_feature_variants):
@@ -149,8 +149,8 @@ def test_strategy_variant_is_returned(test_feature_strategy_variants):
 
     assert variant == {
         "enabled": True,
-        "name": "VarB",
-        "payload": {"type": "string", "value": "Test 2"},
+        "name": "VarC",
+        "payload": {"type": "string", "value": "Test 3"},
     }
 
 

tests/unit_tests/test_variants.py

@@ -55,7 +55,7 @@ def test_variation_selectvariation_happypath(variations):
     variant = variations.get_variant({"userId": "2"})
     assert variant
     assert "payload" in variant
-    assert variant["name"] == "VarC"
+    assert variant["name"] == "VarA"
 
 
 def test_variation_customvariation(variations_with_stickiness):