Merge pull request #9 from evo-company/fix-hashing-algo-different-see…

…d-on-workers

fix hash function to work on different workers the same

featureflags_client/http/conditions.py

@@ -3,6 +3,7 @@
 from typing import Any, Callable, Dict, List, Optional, Set
 
 from featureflags_client.http.types import Check, Flag, Operator
+from featureflags_client.http.utils import hash_flag_value
 
 log = logging.getLogger(__name__)
 
@@ -79,7 +80,11 @@ def percent(name: str, value: Any) -> Callable:
     @except_false
     def proc(ctx: Dict[str, Any]) -> bool:
         ctx_val = ctx.get(name, _UNDEFINED)
-        return ctx_val is not _UNDEFINED and hash(ctx_val) % 100 < int(value)
+        if ctx_val is _UNDEFINED:
+            return False
+
+        hash_ctx_val = hash_flag_value(name, ctx_val)
+        return hash_ctx_val % 100 < int(value)
 
     return proc
 

featureflags_client/http/utils.py

@@ -1,4 +1,6 @@
+import hashlib
 import inspect
+import struct
 from enum import Enum, EnumMeta
 from typing import Any, Dict, Generator, Mapping, Type, Union
 
@@ -54,3 +56,9 @@ def intervals_gen(
         else:
             success = yield retry_interval
             retry_interval = min(retry_interval * 2, retry_interval_max)
+
+
+def hash_flag_value(name: str, value: Any) -> int:
+    hash_digest = hashlib.md5(f"{name}{value}".encode()).digest()  # noqa: S324
+    (hash_int,) = struct.unpack("<L", hash_digest[-4:])
+    return hash_int

featureflags_client/tests/http/test_conditions.py

@@ -19,10 +19,15 @@
     wildcard,
 )
 from featureflags_client.http.types import Operator
+from featureflags_client.http.utils import hash_flag_value
+
+TEST_OPERATOR_NAME = "test_operator"
+TEST_VARIABLE_NAME = "test_operator"
 
 
 def check_op(left: Any, op: Callable, right: Any) -> bool:
-    return op("var", right)({"var": left} if left is not _UNDEFINED else {})
+    context = {TEST_VARIABLE_NAME: left} if left is not _UNDEFINED else {}
+    return op(TEST_OPERATOR_NAME, right)(context)
 
 
 def test_false():
@@ -82,24 +87,30 @@ def test_contains():
 
 
 def test_percent():
-    assert check_op(0, percent, 1) is True
-    assert check_op(1, percent, 1) is False
-    assert check_op(1, percent, 2) is True
-
+    # If percent <= 0 return False
     for i in range(-150, 150):
         assert check_op(i, percent, 0) is False
+
+    # If percent >= 100 return True
     for i in range(-150, 150):
         assert check_op(i, percent, 100) is True
 
-    assert check_op("foo", percent, 100) is True
-    assert check_op("foo", percent, 0) is False
-    assert check_op("foo", percent, hash("foo") % 100 + 1) is True
-    assert check_op("foo", percent, hash("foo") % 100 - 1) is False
-
+    # Check not integer values
     assert check_op(_UNDEFINED, percent, 100) is False
+    assert check_op(50, percent, _UNDEFINED) is False
+    assert check_op(_UNDEFINED, percent, _UNDEFINED) is False
+    assert check_op("foo", percent, "not_number") is False
 
+    # Check string values
     assert check_op("foo", percent, "100") is True
-    assert check_op("foo", percent, "not_number") is False
+    assert check_op("foo", percent, "0") is False
+    assert check_op("foo", percent, 100) is True
+    assert check_op("foo", percent, 0) is False
+
+    # Check hash comparison
+    foo_hash = hash_flag_value(TEST_VARIABLE_NAME, "foo")
+    assert check_op("foo", percent, foo_hash % 100 + 1) is True
+    assert check_op("foo", percent, foo_hash % 100 - 1) is False
 
 
 def test_regexp():