+class FileLoggingMiddleware:
+ """ Middleware to log selected requests into a file.
+ """
+
+ def __init__(self, file_name: str):
+ self.fd = open(file_name, 'a', buffering=1, encoding='utf8') # pylint: disable=R1732
+
+
+ async def process_request(self, req: Request, _: Response) -> None:
+ """ Callback before the request starts timing.
+ """
+ req.context.start = dt.datetime.now(tz=dt.timezone.utc)
+
+
+ async def process_response(self, req: Request, resp: Response,
+ resource: Optional[EndpointWrapper],
+ req_succeeded: bool) -> None:
+ """ Callback after requests writes to the logfile. It only
+ writes logs for sucessful requests for search, reverse and lookup.
+ """
+ if not req_succeeded or resource is None or resp.status != 200\
+ or resource.name not in ('reverse', 'search', 'lookup'):
+ return
+
+ finish = dt.datetime.now(tz=dt.timezone.utc)
+ duration = (finish - req.context.start).total_seconds()
+ params = req.scope['query_string'].decode('utf8')
+ start = req.context.start.replace(tzinfo=None)\
+ .isoformat(sep=' ', timespec='milliseconds')
+
+ self.fd.write(f"[{start}] "
+ f"{duration:.4f} {getattr(resp.context, 'num_results', 0)} "
+ f'{resource.name} "{params}"\n')
+
+