Add and document a logging filter

Author: leplatrem

docs/fastapi.rst

@@ -293,10 +293,16 @@ for at least the ``request.summary`` logger:
                 'logger_name': 'myproject'
             }
         },
+        'filters': {
+            'request_id': {
+                '()': 'dockerflow.fastapi.RequestIdFilter',
+            },
+        },
         'handlers': {
             'console': {
                 'level': 'DEBUG',
                 'class': 'logging.StreamHandler',
+                'filters': ['request_id'],
                 'formatter': 'json'
             },
         },

src/dockerflow/fastapi/__init__.py

@@ -1,3 +1,6 @@
+from logging import Filter, LogRecord
+
+from asgi_correlation_id import correlation_id
 from fastapi import APIRouter
 from fastapi.routing import APIRoute
 
@@ -12,3 +15,14 @@
     ],
 )
 """This router adds the Dockerflow views."""
+
+
+class RequestIdLogFilter(Filter):
+    """Logging filter to attach request IDs to log records"""
+
+    def filter(self, record: "LogRecord") -> bool:
+        """
+        Attach the request ID to the log record.
+        """
+        record.rid = correlation_id.get(None)
+        return True

tests/fastapi/test_fastapi.py

@@ -9,6 +9,7 @@
 from fastapi.testclient import TestClient
 
 from dockerflow import checks
+from dockerflow.fastapi import RequestIdLogFilter
 from dockerflow.fastapi import router as dockerflow_router
 from dockerflow.fastapi.middleware import (
     CorrelationIdMiddleware,
@@ -77,6 +78,40 @@ def test_mozlog_request_id(client, caplog):
     assert record.rid == "tracked-value"
 
 
+def test_mozlog_without_correlation_id_middleware(client, caplog):
+    app = FastAPI()
+    app.include_router(dockerflow_router)
+    app.add_middleware(MozlogRequestSummaryLogger)
+    client = TestClient(app)
+
+    client.get("/__lbheartbeat__")
+    record = caplog.records[0]
+
+    assert record.rid is None
+
+
+def test_request_id_passed_to_all_log_messages(caplog):
+    handler = logging.StreamHandler()
+    handler.addFilter(RequestIdLogFilter())
+    _logger = logging.getLogger("some_logger")
+    _logger.addHandler(handler)
+
+    app = create_app()
+
+    @app.get("/ping")
+    def ping():
+        logger = logging.getLogger("some_logger")
+        logger.info("returning pong")
+        return "pong"
+
+    client = TestClient(app)
+
+    client.get("/ping")
+
+    log_message = next(r for r in caplog.records if r.name == "some_logger")
+    assert log_message.rid is not None
+
+
 def test_mozlog_failure(client, mocker, caplog):
     mocker.patch(
         "dockerflow.fastapi.views.get_version", side_effect=ValueError("crash")