wire service resource detector in declarative config

Adds service detector support to _run_detectors(): sets a random UUID
for service.instance.id and reads OTEL_SERVICE_NAME for service.name
if set. Explicit config attributes still take priority (merged last).

Assisted-by: Claude Sonnet 4.6

Author: MikeGoldsmith

opentelemetry-sdk/src/opentelemetry/sdk/_configuration/_resource.py

@@ -16,6 +16,8 @@
 
 import fnmatch
 import logging
+import os
+import uuid
 from typing import Callable, Optional
 from urllib import parse
 
@@ -28,6 +30,8 @@
 from opentelemetry.sdk._configuration.models import Resource as ResourceConfig
 from opentelemetry.sdk.resources import (
     _DEFAULT_RESOURCE,
+    OTEL_SERVICE_NAME,
+    SERVICE_INSTANCE_ID,
     SERVICE_NAME,
     Resource,
 )
@@ -149,6 +153,14 @@ def _run_detectors(
     is updated in-place; later detectors overwrite earlier ones for the
     same key.
     """
+    if detector_config.service is not None:
+        attrs: dict[str, object] = {
+            SERVICE_INSTANCE_ID: str(uuid.uuid4()),
+        }
+        service_name = os.environ.get(OTEL_SERVICE_NAME)
+        if service_name:
+            attrs[SERVICE_NAME] = service_name
+        detected_attrs.update(attrs)
 
 
 def _filter_attributes(

opentelemetry-sdk/tests/_configuration/test_resource.py

@@ -20,9 +20,13 @@
 from opentelemetry.sdk._configuration.models import (
     AttributeNameValue,
     AttributeType,
+    ExperimentalResourceDetection,
+    ExperimentalResourceDetector,
+    IncludeExclude,
 )
 from opentelemetry.sdk._configuration.models import Resource as ResourceConfig
 from opentelemetry.sdk.resources import (
+    SERVICE_INSTANCE_ID,
     SERVICE_NAME,
     TELEMETRY_SDK_LANGUAGE,
     TELEMETRY_SDK_NAME,
@@ -295,3 +299,75 @@ def test_attributes_list_invalid_pair_skipped(self):
         self.assertEqual(resource.attributes["foo"], "bar")
         self.assertNotIn("no-equals", resource.attributes)
         self.assertTrue(any("no-equals" in msg for msg in cm.output))
+
+
+class TestServiceResourceDetector(unittest.TestCase):
+    def _config_with_service(self) -> ResourceConfig:
+        return ResourceConfig(
+            detection_development=ExperimentalResourceDetection(
+                detectors=[ExperimentalResourceDetector(service={})]
+            )
+        )
+
+    def test_service_detector_adds_instance_id(self):
+        resource = create_resource(self._config_with_service())
+        self.assertIn(SERVICE_INSTANCE_ID, resource.attributes)
+
+    def test_service_instance_id_is_unique_per_call(self):
+        r1 = create_resource(self._config_with_service())
+        r2 = create_resource(self._config_with_service())
+        self.assertNotEqual(
+            r1.attributes[SERVICE_INSTANCE_ID],
+            r2.attributes[SERVICE_INSTANCE_ID],
+        )
+
+    def test_service_detector_reads_otel_service_name_env_var(self):
+        with patch.dict(os.environ, {"OTEL_SERVICE_NAME": "my-service"}):
+            resource = create_resource(self._config_with_service())
+        self.assertEqual(resource.attributes[SERVICE_NAME], "my-service")
+
+    def test_service_detector_no_env_var_leaves_default_service_name(self):
+        with patch.dict(os.environ, {}, clear=True):
+            resource = create_resource(self._config_with_service())
+        self.assertEqual(resource.attributes[SERVICE_NAME], "unknown_service")
+
+    def test_explicit_service_name_overrides_env_var(self):
+        """Config attributes win over the service detector's env-var value."""
+        config = ResourceConfig(
+            attributes=[
+                AttributeNameValue(name="service.name", value="explicit-svc")
+            ],
+            detection_development=ExperimentalResourceDetection(
+                detectors=[ExperimentalResourceDetector(service={})]
+            ),
+        )
+        with patch.dict(os.environ, {"OTEL_SERVICE_NAME": "env-svc"}):
+            resource = create_resource(config)
+        self.assertEqual(resource.attributes[SERVICE_NAME], "explicit-svc")
+
+    def test_service_detector_not_run_when_absent(self):
+        resource = create_resource(ResourceConfig())
+        self.assertNotIn(SERVICE_INSTANCE_ID, resource.attributes)
+
+    def test_service_detector_not_run_when_detection_development_is_none(self):
+        resource = create_resource(ResourceConfig(detection_development=None))
+        self.assertNotIn(SERVICE_INSTANCE_ID, resource.attributes)
+
+    def test_service_detector_also_includes_sdk_defaults(self):
+        resource = create_resource(self._config_with_service())
+        self.assertEqual(resource.attributes[TELEMETRY_SDK_LANGUAGE], "python")
+        self.assertIn(TELEMETRY_SDK_VERSION, resource.attributes)
+
+    def test_included_filter_limits_service_attributes(self):
+        config = ResourceConfig(
+            detection_development=ExperimentalResourceDetection(
+                detectors=[ExperimentalResourceDetector(service={})],
+                attributes=IncludeExclude(included=["service.instance.id"]),
+            )
+        )
+        with patch.dict(os.environ, {"OTEL_SERVICE_NAME": "my-service"}):
+            resource = create_resource(config)
+        self.assertIn(SERVICE_INSTANCE_ID, resource.attributes)
+        # service.name comes from the filter-excluded detector output, but the
+        # default "unknown_service" is still added by create_resource directly
+        self.assertEqual(resource.attributes[SERVICE_NAME], "unknown_service")