Allow passing a custom random number generator to trace.RandomIdGenerator

CHANGELOG.md

@@ -7,6 +7,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## Unreleased
 
+- Allow passing a custom random number generator to `trace.RandomIdGenerator`.
+  ([#4571](https://github.com/open-telemetry/opentelemetry-python/pull/4571))
 - typecheck: add sdk/resources and drop mypy
   ([#4578](https://github.com/open-telemetry/opentelemetry-python/pull/4578))
 - Refactor `BatchLogRecordProcessor` to simplify code and make the control flow more

opentelemetry-sdk/src/opentelemetry/sdk/trace/id_generator.py

@@ -14,6 +14,8 @@
 
 import abc
 import random
+from random import Random
+from typing import Optional
 
 from opentelemetry import trace
 
@@ -45,16 +47,29 @@ def generate_trace_id(self) -> int:
 class RandomIdGenerator(IdGenerator):
     """The default ID generator for TracerProvider which randomly generates all
     bits when generating IDs.
+
+    Args:
+        rng: A random number generator. Defaults to the global random instance.
+            It is recommended to use a fresh `Random()` instead of the default
+            to avoid potential conflicts with the global random instance
+            (duplicate ids across multiple processes when a constant global
+            random seed is set). In case of a custom implementation, it should
+            be uniform, as some samplers rely on this randomness to make sampling decisions.
     """
 
+    def __init__(self, rng: Optional[Random] = None) -> None:
+        if rng is None:
+            rng = random  # Just a hack to preserve backward compatibility, otherwise it does not quite match the type hint.
+        self._rng = rng
+
     def generate_span_id(self) -> int:
-        span_id = random.getrandbits(64)
+        span_id = self._rng.getrandbits(64)
         while span_id == trace.INVALID_SPAN_ID:
-            span_id = random.getrandbits(64)
+            span_id = self._rng.getrandbits(64)
         return span_id
 
     def generate_trace_id(self) -> int:
-        trace_id = random.getrandbits(128)
+        trace_id = self._rng.getrandbits(128)
         while trace_id == trace.INVALID_TRACE_ID:
-            trace_id = random.getrandbits(128)
+            trace_id = self._rng.getrandbits(128)
         return trace_id

opentelemetry-sdk/tests/trace/test_trace.py

@@ -20,7 +20,7 @@
 import unittest
 from importlib import reload
 from logging import ERROR, WARNING
-from random import randint
+from random import randint, Random
 from time import time_ns
 from typing import Optional
 from unittest import mock
@@ -2168,29 +2168,29 @@ class TestRandomIdGenerator(unittest.TestCase):
     _TRACE_ID_MAX_VALUE = 2**128 - 1
     _SPAN_ID_MAX_VALUE = 2**64 - 1
 
-    @patch(
-        "random.getrandbits",
-        side_effect=[trace_api.INVALID_SPAN_ID, 0x00000000DEADBEF0],
-    )
-    def test_generate_span_id_avoids_invalid(self, mock_getrandbits):
-        generator = RandomIdGenerator()
-        span_id = generator.generate_span_id()
-
-        self.assertNotEqual(span_id, trace_api.INVALID_SPAN_ID)
-        mock_getrandbits.assert_any_call(64)
-        self.assertEqual(mock_getrandbits.call_count, 2)
-
-    @patch(
-        "random.getrandbits",
-        side_effect=[
-            trace_api.INVALID_TRACE_ID,
-            0x000000000000000000000000DEADBEEF,
-        ],
-    )
-    def test_generate_trace_id_avoids_invalid(self, mock_getrandbits):
-        generator = RandomIdGenerator()
-        trace_id = generator.generate_trace_id()
+    def setUp(self):
+        self.generators = {
+            'rng=None': RandomIdGenerator(),
+            'rng=Random()': RandomIdGenerator(rng=Random()),
+            'rng=Random(42)': RandomIdGenerator(rng=Random(x=42))
+        }
 
-        self.assertNotEqual(trace_id, trace_api.INVALID_TRACE_ID)
-        mock_getrandbits.assert_any_call(128)
-        self.assertEqual(mock_getrandbits.call_count, 2)
+    def test_generate_span_id_avoids_invalid(self):
+        for msg, generator in self.generators.items():
+            with self.subTest(msg=msg), \
+                    patch.object(generator._rng, "getrandbits", side_effect=[trace_api.INVALID_SPAN_ID, 0x00000000DEADBEF0]) as mock_getrandbits:
+                span_id = generator.generate_span_id()
+
+                self.assertNotEqual(span_id, trace_api.INVALID_SPAN_ID)
+                mock_getrandbits.assert_any_call(64)
+                self.assertEqual(mock_getrandbits.call_count, 2)
+
+    def test_generate_trace_id_avoids_invalid(self):
+        for name, generator in self.generators.items():
+            with self.subTest(msg=name), \
+                    patch.object(generator._rng, "getrandbits", side_effect=[trace_api.INVALID_TRACE_ID, 0x000000000000000000000000DEADBEEF]) as mock_getrandbits:
+                trace_id = generator.generate_trace_id()
+
+                self.assertNotEqual(trace_id, trace_api.INVALID_TRACE_ID)
+                mock_getrandbits.assert_any_call(128)
+                self.assertEqual(mock_getrandbits.call_count, 2)