feat(config): wire container resource detector via entry point loading (#5004)

* config: add resource and propagator creation from declarative config

Implements create_resource() and create_propagator()/configure_propagator()
for the declarative file configuration. Resource creation does not read
OTEL_RESOURCE_ATTRIBUTES or run any detectors (matches Java/JS SDK behavior).
Propagator configuration always calls set_global_textmap to override Python's
default tracecontext+baggage, setting a noop CompositePropagator when no
propagator is configured.

Assisted-by: Claude Sonnet 4.6

* update changelog with PR number

Assisted-by: Claude Sonnet 4.6

* fix pylint, pyright and ruff errors in resource/propagator config

- _resource.py: refactor _coerce_attribute_value to dispatch table to
  avoid too-many-return-statements; fix short variable names k/v ->
  attr_key/attr_val; fix return type of _sdk_default_attributes to
  dict[str, str] to satisfy pyright
- _propagator.py: rename short variable names e -> exc, p -> propagator
- test_resource.py: move imports to top level; split TestCreateResource
  (25 methods) into three focused classes to satisfy too-many-public-methods
- test_propagator.py: add pylint disable for protected-access

Assisted-by: Claude Sonnet 4.6

* address review feedback: use _DEFAULT_RESOURCE, fix bool_array coercion

- replace _sdk_default_attributes() with _DEFAULT_RESOURCE from resources module
- move _coerce_bool into dispatch tables for both scalar and array bool types,
  fixing a bug where bool_array with string values like "false" would coerce
  incorrectly via plain bool() (non-empty string -> True)
- add test for bool_array with string values to cover the bug

Assisted-by: Claude Sonnet 4.6

* fix linter

* address review feedback: single coercion table, simplify attributes merge

- collapse _SCALAR_COERCIONS and _ARRAY_COERCIONS into a single _COERCIONS
  dict using an _array() factory, reducing _coerce_attribute_value to two lines
- process attributes_list before attributes so explicit attributes naturally
  overwrite list entries without needing an explicit guard

Assisted-by: Claude Sonnet 4.6

* use Callable type annotation on _array helper

Assisted-by: Claude Sonnet 4.6

* add detection infrastructure foundations for resource detectors

Adds _run_detectors() stub and _filter_attributes() to create_resource(),
providing the shared scaffolding for detector PRs to build on. Detectors
are opt-in: nothing runs unless explicitly listed under
detection_development.detectors in the config. The include/exclude
attribute filter mirrors other SDK behaviour.

Assisted-by: Claude Sonnet 4.6

* move service.name default into base resource

Merges service.name=unknown_service into base before running detectors,
so detectors (e.g. service) can override it. Previously it was added to
config_attrs and merged last, which would have silently overridden any
detector-provided service.name.

Assisted-by: Claude Sonnet 4.6

* remove unused logging import from _propagator.py

Assisted-by: Claude Sonnet 4.6

* wire container resource detector in declarative config

When `resource.detection_development.detectors[].container` is set in
the config file, attempt to use `ContainerResourceDetector` from the
`opentelemetry-resource-detector-containerid` contrib package. Unlike
the process, host, and service detectors which are implemented in the
core SDK, container detection is not available in core. Rather than
adding a hard dependency on the contrib package, we use a lazy import:
if the package is installed it is used transparently; if absent a
warning is logged with an actionable install instruction.

This mirrors the approach taken by other SDKs: JS explicitly skips
container detection when no implementation is available, and PHP also
defers container detection to a contrib package.

See: open-telemetry/opentelemetry-configuration#570

Assisted-by: Claude Sonnet 4.6

* add changelog entry for container resource detector (#5004)

Assisted-by: Claude Sonnet 4.6

* add pylint disables for lazy container import in _resource.py

Assisted-by: Claude Sonnet 4.6

* load container detector via entry point instead of lazy import

Matches the env-var config counterpart (OTEL_EXPERIMENTAL_RESOURCE_DETECTORS)
and avoids a hard import dependency on the contrib package. Tests updated
to mock entry_points instead of sys.modules.

Assisted-by: Claude Sonnet 4.6

Author: MikeGoldsmith

CHANGELOG.md

@@ -12,6 +12,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## Unreleased
 
+- `opentelemetry-sdk`: Add `container` resource detector support to declarative file configuration via `detection_development.detectors[].container`, using entry point loading of the `opentelemetry-resource-detector-containerid` contrib package
+  ([#5004](https://github.com/open-telemetry/opentelemetry-python/pull/5004))
 - `opentelemetry-sdk`: Add `create_tracer_provider`/`configure_tracer_provider` to declarative file configuration, enabling TracerProvider instantiation from config files without reading env vars
   ([#4985](https://github.com/open-telemetry/opentelemetry-python/pull/4985))
 - Enabled the flake8-tidy-import plugins rules for the ruff linter. These rules throw warnings for relative imports in the modules.

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

@@ -32,6 +32,7 @@
     ProcessResourceDetector,
     Resource,
 )
+from opentelemetry.util._importlib_metadata import entry_points
 
 _logger = logging.getLogger(__name__)
 
@@ -150,6 +151,30 @@ def _run_detectors(
     is updated in-place; later detectors overwrite earlier ones for the
     same key.
     """
+    if detector_config.container is not None:
+        # The container detector is not part of the core SDK. It is provided
+        # by the opentelemetry-resource-detector-containerid contrib package,
+        # which registers itself under the opentelemetry_resource_detector
+        # entry point group as "container". Loading via entry point matches
+        # the env-var config counterpart (OTEL_EXPERIMENTAL_RESOURCE_DETECTORS)
+        # and avoids a hard import dependency on contrib. See also:
+        # https://github.com/open-telemetry/opentelemetry-configuration/issues/570
+        ep = next(
+            iter(
+                entry_points(
+                    group="opentelemetry_resource_detector", name="container"
+                )
+            ),
+            None,
+        )
+        if ep is None:
+            _logger.warning(
+                "container resource detector requested but "
+                "'opentelemetry-resource-detector-containerid' is not "
+                "installed; install it to enable container detection"
+            )
+        else:
+            detected_attrs.update(ep.load()().detect().attributes)
     if detector_config.process is not None:
         detected_attrs.update(ProcessResourceDetector().detect().attributes)
 

opentelemetry-sdk/tests/_configuration/test_resource.py

@@ -15,7 +15,7 @@
 import os
 import sys
 import unittest
-from unittest.mock import patch
+from unittest.mock import MagicMock, patch
 
 from opentelemetry.sdk._configuration._resource import create_resource
 from opentelemetry.sdk._configuration.models import (
@@ -26,6 +26,7 @@
 )
 from opentelemetry.sdk._configuration.models import Resource as ResourceConfig
 from opentelemetry.sdk.resources import (
+    CONTAINER_ID,
     PROCESS_PID,
     PROCESS_RUNTIME_NAME,
     SERVICE_NAME,
@@ -302,6 +303,91 @@ def test_attributes_list_invalid_pair_skipped(self):
         self.assertTrue(any("no-equals" in msg for msg in cm.output))
 
 
+class TestContainerResourceDetector(unittest.TestCase):
+    @staticmethod
+    def _config_with_container() -> ResourceConfig:
+        return ResourceConfig(
+            detection_development=ExperimentalResourceDetection(
+                detectors=[ExperimentalResourceDetector(container={})]
+            )
+        )
+
+    def test_container_detector_not_run_when_absent(self):
+        resource = create_resource(ResourceConfig())
+        self.assertNotIn(CONTAINER_ID, resource.attributes)
+
+    def test_container_detector_not_run_when_detection_development_is_none(
+        self,
+    ):
+        resource = create_resource(ResourceConfig(detection_development=None))
+        self.assertNotIn(CONTAINER_ID, resource.attributes)
+
+    def test_container_detector_not_run_when_detectors_list_empty(self):
+        config = ResourceConfig(
+            detection_development=ExperimentalResourceDetection(detectors=[])
+        )
+        resource = create_resource(config)
+        self.assertNotIn(CONTAINER_ID, resource.attributes)
+
+    def test_container_detector_warns_when_package_missing(self):
+        """A warning is logged when the contrib entry point is not found."""
+        with patch(
+            "opentelemetry.sdk._configuration._resource.entry_points",
+            return_value=[],
+        ):
+            with self.assertLogs(
+                "opentelemetry.sdk._configuration._resource", level="WARNING"
+            ) as cm:
+                resource = create_resource(self._config_with_container())
+        self.assertNotIn(CONTAINER_ID, resource.attributes)
+        self.assertTrue(
+            any(
+                "opentelemetry-resource-detector-containerid" in msg
+                for msg in cm.output
+            )
+        )
+
+    def test_container_detector_uses_contrib_when_available(self):
+        """When the contrib entry point is registered, container.id is detected."""
+        mock_resource = Resource({CONTAINER_ID: "abc123"})
+        mock_detector = MagicMock()
+        mock_detector.return_value.detect.return_value = mock_resource
+        mock_ep = MagicMock()
+        mock_ep.load.return_value = mock_detector
+
+        with patch(
+            "opentelemetry.sdk._configuration._resource.entry_points",
+            return_value=[mock_ep],
+        ):
+            resource = create_resource(self._config_with_container())
+
+        self.assertEqual(resource.attributes[CONTAINER_ID], "abc123")
+
+    def test_explicit_attributes_override_container_detector(self):
+        """Config attributes win over detector-provided values."""
+        mock_resource = Resource({CONTAINER_ID: "detected-id"})
+        mock_detector = MagicMock()
+        mock_detector.return_value.detect.return_value = mock_resource
+        mock_ep = MagicMock()
+        mock_ep.load.return_value = mock_detector
+
+        config = ResourceConfig(
+            attributes=[
+                AttributeNameValue(name="container.id", value="explicit-id")
+            ],
+            detection_development=ExperimentalResourceDetection(
+                detectors=[ExperimentalResourceDetector(container={})]
+            ),
+        )
+        with patch(
+            "opentelemetry.sdk._configuration._resource.entry_points",
+            return_value=[mock_ep],
+        ):
+            resource = create_resource(config)
+
+        self.assertEqual(resource.attributes[CONTAINER_ID], "explicit-id")
+
+
 class TestProcessResourceDetector(unittest.TestCase):
     @staticmethod
     def _config_with_process() -> ResourceConfig: