Refactored DJB2 code for Application Insights Sampler (#42210)

* Refactored DJB2 code for Application Insights Sampler

* Updated CHANGELOG

Author: rads-1996

sdk/monitor/azure-monitor-opentelemetry-exporter/CHANGELOG.md

@@ -24,6 +24,8 @@
   ([#41971](https://github.com/Azure/azure-sdk-for-python/pull/41971))
 - Added RateLimited Sampler 
   ([#41954](https://github.com/Azure/azure-sdk-for-python/pull/41954))
+- Refactored Application Insights Sampler Code
+  ([#42210](https://github.com/Azure/azure-sdk-for-python/pull/42210))
 
 - Support AI Foundry by Handling GEN_AI_SYSTEM Attributes with [Spec](https://github.com/aep-health-and-standards/Telemetry-Collection-Spec/blob/main/ApplicationInsights/genai_semconv_mapping.md) ([#41705](https://github.com/Azure/azure-sdk-for-python/pull/41705))
 

sdk/monitor/azure-monitor-opentelemetry-exporter/azure/monitor/opentelemetry/exporter/export/trace/_sampling.py

@@ -2,9 +2,6 @@
 # Licensed under the MIT License.
 from typing import Optional, Sequence
 
-# pylint:disable=no-name-in-module
-from fixedint import Int32
-
 from opentelemetry.context import Context
 from opentelemetry.trace import Link, SpanKind, format_trace_id
 from opentelemetry.sdk.trace.sampling import (
@@ -16,12 +13,10 @@
 from opentelemetry.trace.span import TraceState
 from opentelemetry.util.types import Attributes
 
-from azure.monitor.opentelemetry.exporter._constants import _SAMPLE_RATE_KEY
+from azure.monitor.opentelemetry.exporter.export.trace._utils import _get_DJB2_sample_score
 
+from azure.monitor.opentelemetry.exporter._constants import _SAMPLE_RATE_KEY
 
-_HASH = 5381
-_INTEGER_MAX: int = Int32.maxval
-_INTEGER_MIN: int = Int32.minval
 
 
 # Sampler is responsible for the following:
@@ -57,7 +52,7 @@ def should_sample(
             decision = Decision.RECORD_AND_SAMPLE
         else:
             # Determine if should sample from ratio and traceId
-            sample_score = self._get_DJB2_sample_score(format_trace_id(trace_id).lower())
+            sample_score = _get_DJB2_sample_score(format_trace_id(trace_id).lower())
             if sample_score < self._ratio:
                 decision = Decision.RECORD_AND_SAMPLE
             else:
@@ -72,20 +67,6 @@ def should_sample(
             _get_parent_trace_state(parent_context),  # type: ignore
         )
 
-    def _get_DJB2_sample_score(self, trace_id_hex: str) -> float:
-        # This algorithm uses 32bit integers
-        hash_value = Int32(_HASH)
-        for char in trace_id_hex:
-            hash_value = ((hash_value << 5) + hash_value) + ord(char)
-
-        if hash_value == _INTEGER_MIN:
-            hash_value = int(_INTEGER_MAX)
-        else:
-            hash_value = abs(hash_value)
-
-        # divide by _INTEGER_MAX for value between 0 and 1 for sampling score
-        return float(hash_value) / _INTEGER_MAX
-
     def get_description(self) -> str:
         return "ApplicationInsightsSampler{}".format(self._ratio)
 

sdk/monitor/azure-monitor-opentelemetry-exporter/tests/trace/test_sampling.py

@@ -26,15 +26,15 @@ def test_invalid_ratio(self):
         self.assertRaises(ValueError, lambda: ApplicationInsightsSampler(1.01))
         self.assertRaises(ValueError, lambda: ApplicationInsightsSampler(-0.01))
 
-    @mock.patch.object(ApplicationInsightsSampler, "_get_DJB2_sample_score")
+    @mock.patch("azure.monitor.opentelemetry.exporter.export.trace._sampling._get_DJB2_sample_score")
     def test_should_sample(self, score_mock):
         sampler = ApplicationInsightsSampler(0.75)
         score_mock.return_value = 0.7
         result = sampler.should_sample(None, 0, "test")
         self.assertEqual(result.attributes["_MS.sampleRate"], 75)
         self.assertTrue(result.decision.is_sampled())
 
-    @mock.patch.object(ApplicationInsightsSampler, "_get_DJB2_sample_score")
+    @mock.patch("azure.monitor.opentelemetry.exporter.export.trace._sampling._get_DJB2_sample_score")
     def test_should_sample_not_sampled(self, score_mock):
         sampler = ApplicationInsightsSampler(0.5)
         score_mock.return_value = 0.7