Fix/copy measurement attributes

CHANGELOG.md

@@ -14,6 +14,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 - docs: Added sqlcommenter example
   ([#4734](https://github.com/open-telemetry/opentelemetry-python/pull/4734))
+- opentelemetry-sdk: `Measurement`s `Attributes` are now copied when instantiating a `Measurement`. This stops the accidental modification of `Attibutes` after the `Measurement` is created.
+  ([#4627](https://github.com/open-telemetry/opentelemetry-python/pull/4627))
 
 ## Version 1.38.0/0.59b0 (2025-10-16)
 

opentelemetry-sdk/src/opentelemetry/sdk/metrics/_internal/measurement.py

@@ -11,7 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
-
+from copy import deepcopy
 from dataclasses import dataclass
 from typing import Union
 
@@ -43,3 +43,10 @@ class Measurement:
     instrument: Instrument
     context: Context
     attributes: Attributes = None
+
+    def __post_init__(self) -> None:
+        if self.attributes is not None:
+            super().__setattr__(
+                "attributes",
+                deepcopy(self.attributes),
+            )

opentelemetry-sdk/tests/metrics/integration_test/test_data_point_creation.py

@@ -0,0 +1,61 @@
+import pytest
+
+from opentelemetry.sdk.metrics import Meter, MeterProvider
+from opentelemetry.sdk.metrics.export import (
+    InMemoryMetricReader,
+)
+from opentelemetry.util.types import Attributes
+
+
+@pytest.fixture
+def attributes() -> Attributes:
+    return {
+        "key": "value",
+    }
+
+
+@pytest.fixture
+def meter_name() -> str:
+    return "test_meter"
+
+
+@pytest.fixture
+def reader() -> InMemoryMetricReader:
+    return InMemoryMetricReader()
+
+
+@pytest.fixture
+def meter_provider(reader: InMemoryMetricReader) -> MeterProvider:
+    return MeterProvider(metric_readers=[reader])
+
+
+@pytest.fixture
+def meter(meter_provider: MeterProvider, meter_name: str) -> Meter:
+    return meter_provider.get_meter("test_meter")
+
+
+def test_measurement_collection(
+    reader: InMemoryMetricReader,
+    meter: Meter,
+    attributes: Attributes,
+) -> None:
+    """
+    Validate that adjusting attributes after a data point is created does not affect
+    the already collected measurement.
+    """
+    counter = meter.create_counter("test_counter")
+    counter.add(1, attributes)
+    attributes["key"] = "new_value"
+    counter.add(1, attributes)
+
+    reader.collect()
+
+    metrics_data = reader.get_metrics_data()
+    resource_metric, *_ = metrics_data.resource_metrics
+    scope_metric, *_ = resource_metric.scope_metrics
+    metrics, *_ = scope_metric.metrics
+    data = metrics.data
+    data_point_1, data_point_2 = data.data_points
+
+    assert data_point_1.attributes == {"key": "value"}
+    assert data_point_2.attributes == {"key": "new_value"}

opentelemetry-sdk/tests/metrics/test_measurement.py

@@ -0,0 +1,66 @@
+from unittest.mock import Mock
+
+import pytest
+
+from opentelemetry.context import Context
+from opentelemetry.metrics import Instrument
+from opentelemetry.sdk.metrics._internal.measurement import (
+    Measurement,
+)
+from opentelemetry.util.types import Attributes
+
+
+@pytest.fixture
+def attributes() -> Attributes:
+    return {
+        "key": "value",
+    }
+
+
+@pytest.fixture
+def unix_time() -> int:
+    return 1761568368250037000
+
+
+@pytest.fixture
+def context() -> Context:
+    return Context()
+
+
+@pytest.fixture
+def instrument():
+    return Mock(spec=Instrument)
+
+
+@pytest.fixture
+def measurement(
+    unix_time: int,
+    instrument: Instrument,
+    context: Context,
+    attributes: Attributes,
+) -> Measurement:
+    return Measurement(
+        value=1.0,
+        time_unix_nano=unix_time,
+        instrument=instrument,
+        context=context,
+        attributes=attributes,
+    )
+
+
+def test_measurement_attribute_is_a_different_object(
+    measurement: Measurement,
+    attributes: Attributes,
+):
+    assert measurement.attributes is not attributes
+
+
+def test_measurement_attribute_uneffected_by_change(
+    measurement: Measurement,
+    attributes: Attributes,
+) -> None:
+    attributes["new_key"] = "new_value"
+
+    assert measurement.attributes == {
+        "key": "value",
+    }