feat: OTel: Task Processor by khvn26 · Pull Request #197 · Flagsmith/flagsmith-common

khvn26 · 2026-04-10T15:35:46Z

Closes #184.

Serialise W3C trace context (traceparent, baggage) into a nullable trace_context JSONField on tasks at enqueue time via propagate.inject() in TaskHandler.delay()
Extract and activate context as a parent span in _run_task(), linking task execution spans back to the originating HTTP request trace
Derive default service.name from entrypoint: flagsmith-task-processor when running the task processor, flagsmith-api otherwise (OTEL_SERVICE_NAME overrides both)
Add opentelemetry-api to task-processor extras, TraceContext type alias, and span attributes matching Prometheus metric labels for cross-signal correlation

How to review

Review complexity: 2/5

Start with the model layer (models.py, types.py, migration) — a new trace_context nullable JSONField. Then follow the write path in decorators.py. Next, the read path in processor.py. Finally, main.py has one conditional for the default service.name based on sys.argv.

Tests mirror the above order: model, decorator, processor, main. The processor tests use static traceparent strings with known hex IDs for parametrisation. span_exporter fixture was promoted from integration test to root conftest, and RunTasksFixture protocol was updated with a default num_tasks.

Test plan

Run Flagsmith API + task processor against a local collector (e.g. SigNoz)
Trigger a request that enqueues a task (e.g. flag update that triggers environment rebuild)
In the trace viewer, verify the task processor span appears as a child of the HTTP request span with matching trace ID
Confirm span attributes (task_identifier, task_type, result) are present
Confirm service.name shows flagsmith-task-processor for task processor spans and flagsmith-api for API spans
Verify structlog events emitted during task execution carry the correct trace_id / span_id

Serialize W3C trace context (traceparent, baggage) into a nullable JSONField on tasks at enqueue time, then extract and activate it as a parent span at execution time. This links task processor spans back to the originating HTTP request trace. - Add `trace_context` JSONField to AbstractBaseTask (migration 0014) - Inject via `propagate.inject()` in `TaskHandler.delay()` - Extract via `propagate.extract()` + span in `_run_task()` - Derive default service.name from entrypoint (flagsmith-task-processor) - Add `opentelemetry-api` to task-processor extras - Promote `span_exporter` fixture to root conftest Closes #184 beep boop

codecov-commenter · 2026-04-10T15:37:35Z

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.05%. Comparing base (1256e87) to head (57c2456).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #197      +/-   ##
==========================================
+ Coverage   96.95%   97.05%   +0.09%     
==========================================
  Files         101      102       +1     
  Lines        4008     4139     +131     
==========================================
+ Hits         3886     4017     +131     
  Misses        122      122

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emyller

Approving because it looks great, my comments are not blocking.

There is one coverage failure I'm suspicious about, but other tests add enough confidence.

emyller · 2026-04-10T23:05:41Z

src/common/core/main.py

+        default_service_name = (
+            "flagsmith-task-processor"
+            if "task-processor" in sys.argv
+            else "flagsmith-api"
+        )


thought: Should we just set OTEL_SERVICE_NAME in container settings? I'm tempted to the smaller effort this allows, but it got my eyebrow raised.

emyller · 2026-04-10T23:13:30Z

tests/unit/common/core/test_main.py

+def test_ensure_cli_env__task_processor__expected_otel_service_name(
+    monkeypatch: pytest.MonkeyPatch,
+    mocker: MockerFixture,
+) -> None:
+    # Given
+    monkeypatch.setattr("sys.argv", ["flagsmith", "task-processor"])
+    monkeypatch.setenv("OTEL_EXPORTER_OTLP_ENDPOINT", "http://collector:4318")
+
+    mock_build_log = mocker.patch(
+        "common.core.otel.build_otel_log_provider",
+        return_value=mocker.MagicMock(spec=LoggerProvider),
+    )
+    mock_build_tracer = mocker.patch(
+        "common.core.otel.build_tracer_provider",
+        return_value=mocker.MagicMock(spec=TracerProvider),
+    )
+    mocker.patch("common.core.otel.setup_tracing")
+
+    # When
+    with ensure_cli_env():
+        pass
+
+    # Then
+    mock_build_log.assert_called_once_with(
+        endpoint="http://collector:4318/v1/logs",
+        service_name="flagsmith-task-processor",
+    )
+    mock_build_tracer.assert_called_once_with(
+        endpoint="http://collector:4318/v1/traces",
+        service_name="flagsmith-task-processor",
+    )


Not sure how the "flagsmith-api" case isn't caught by tests coverage.

Please, either:

Fix coverage;

Consider deleting default_service_name, and this test — see here. IMO test_ensure_cli_env__env_service_name__expected_otel_service_name looks sufficient.

emyller · 2026-04-10T23:20:46Z

tests/unit/task_processor/test_unit_task_processor_processor.py

+    task_spans = [s for s in spans if s.name == dummy_task.task_identifier]
+    assert len(task_spans) == 1
+
+    task_span = task_spans[0]


Suggested change

task_span = task_spans[0]

task_span = task_spans[0]

assert task_span.status.status_code == StatusCode.OK

emyller · 2026-04-10T23:21:05Z

tests/unit/task_processor/test_unit_task_processor_processor.py

+    assert len(task_spans) == 1
+
+    task_span = task_spans[0]
+    assert task_span.attributes is not None


nit

Suggested change

assert task_span.attributes is not None

emyller · 2026-04-10T23:21:37Z

tests/unit/task_processor/test_unit_task_processor_processor.py

+
+    task_span = task_spans[0]
+    assert task_span.status.status_code == StatusCode.ERROR
+    assert task_span.attributes is not None


nit

Suggested change

assert task_span.attributes is not None

emyller · 2026-04-10T23:28:54Z

README.md

 | --------------------------------- | --------------------------------------------------------------------------------------------------------------------- | --------------- |
 | `OTEL_EXPORTER_OTLP_ENDPOINT`     | Base OTLP endpoint (e.g. `http://collector:4318`). If unset, no OTel setup occurs.                                    | _(disabled)_    |
-| `OTEL_SERVICE_NAME`               | The `service.name` resource attribute.                                                                                | `flagsmith-api` |
+| `OTEL_SERVICE_NAME`               | The `service.name` resource attribute. Defaults to `flagsmith-task-processor` when running the task processor.         | `flagsmith-api` |


khvn26 requested a review from a team as a code owner April 10, 2026 15:35

khvn26 requested review from emyller and removed request for a team April 10, 2026 15:35

improve typing, fix coverage

57c2456

khvn26 mentioned this pull request Apr 10, 2026

OTel trace context not added to stdlib log events #198

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feat: OTel: Task Processor#197

feat: OTel: Task Processor#197
khvn26 wants to merge 2 commits intomainfrom
feat/otel-task-processor-trace-context

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	task_span = task_spans[0]
	task_span = task_spans[0]
	assert task_span.status.status_code == StatusCode.OK

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khvn26 commented Apr 10, 2026 •

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