Using @metric_scope with asyncio

[hakenmt]

I have a Lambda function that gets called and it executes a lot of HTTP requests. I'm trying to speed those up through aiohttp. Ultimately I want 1 log entry per http request and 1 log for the actual lambda invocation. I'm running into problems with the metric logger decorating an async method.

Traceback (most recent call last):\n  File \"/var/task/index.py\", line 174, in process_requests\n    code = await send_request(request, context, session)\n  File \"/var/task/aws_embedded_metrics/metric_scope/__init__.py\", line 34, in wrapper\n    await logger.flush()\n  File \"/var/task/aws_embedded_metrics/logger/metrics_logger.py\", line 47, in flush\n    sink.accept(self.context)\n  File \"/var/task/aws_embedded_metrics/sinks/stdout_sink.py\", line 25, in accept\n    for serialized_content in self.serializer.serialize(context):\n  File \"/var/task/aws_embedded_metrics/serializers/log_serializer.py\", line 106, in serialize\n    event_batches.append(json.dumps(current_body))\n  File \"/var/lang/lib/python3.9/json/__init__.py\", line 231, in dumps\n    return _default_encoder.encode(obj)\n  File \"/var/lang/lib/python3.9/json/encoder.py\", line 199, in encode\n    chunks = self.iterencode(o, _one_shot=True)\n  File \"/var/lang/lib/python3.9/json/encoder.py\", line 257, in iterencode\n    return _iterencode(o, 0)\n  File \"/var/lang/lib/python3.9/json/encoder.py\", line 179, in default\n    raise TypeError(f'Object of type {o.__class__.__name__} '\nTypeError: Object of type method is not JSON serializable\n"

This is a basic version of my handler:

# Get event loop
loop = asyncio.get_event_loop()

@metric_scope
def handler(event, context, metrics):
  start = time.perf_counter()
  t = loop.run_until_complete(process_requests(event, context, metrics))
  end = time.perf_counter()
  metrics.put_metric("TotalProcessingLatency", (end - start) * 1000, "Milliseconds")
  return t

The process_requests method:

async def process_requests(event, context, metrics):
  """
  Sets up the aiohttp client and iterates all of the requests
  through the session
  """
  tracebacks = []
  errors = []
  
  async with aiohttp.ClientSession() as session:

    for request in event["requests"]:
      for x in range(0, request["iterations"]):
        try:
          code = await send_request(request, context, session)
        except Exception as e:
          errors.append(str(e))
          tracebacks.append(traceback.format_exc())

  metrics.set_property("Errors", errors)
  metrics.set_property("Tracebacks", tracebacks)
  return None

And finally, the send_request method:

@metric_scope
async def send_request(request, context, session, metrics):
  start = time.time() * 1000
  metrics.set_property("RequestStartTime", round(start))

  async with session.request(method = request["method"],
                                     headers = h,
                                     url = request["url"],
                                     data = str(request["data"]),
                                     ssl = verify,
                                     timeout = request["timeout"]) as response:

    response_end = time.time() * 1000
    metrics.set_property("ResponseReceivedTime", round(response_end))
    metrics.put_metric("RequestLatency", response_end - start, "Milliseconds")
    return response.status_code

This works when I process the HTTP requests synchronously, I get a log for each time send_request is called and once for the overall handler execution. Is there a way I can use the metrics logger and get the same outcome with aiohttp/asyncio?