Python : Logs are not coming in App Insight for async function using eventloop

I am using azure function for one of our python function. We are using eventloop as described in document.

Below is sample of __init__.py

from typing import List
import logging
import json
import asyncio

import azure.functions as func

from .somepackage import SomeClass


async def main(events: List[func.EventHubEvent]):  # pragma: no cover
    """
    Starter function for the azure functions
    @param events:
    @return:
    """
    loop = asyncio.get_event_loop()
    tasks = []
    logging.info("Got %s events" % len(events))
    for idx, event in enumerate(events):
        event_body = json.loads(event.get_body().decode('utf8'))
        properties = event.metadata['PropertiesArray'][idx]
        logging.info("Got Event : %s with properties %s" % (event_body, properties))
        try:

            tasks.append(
                asyncio.create_task(wrapper_function(loop, event_body, properties)))
        except Exception as e:
            logging.exception("Error occurred while processing surface event trigger")
    if tasks:
        result, _ = await asyncio.wait(tasks)
        logging.info("Function : event processing done")


async def wrapper_function(event_loop, event_body, properties):
    some_obj = SomeClass()
    result = await event_loop.run_in_executor(None, some_obj.run, event_body, properties)
    return result

and this is content of somepackage.py file,

import logging


class SomeClass(object):

    def __init__(self):
        logging.info("Object created")

    def run(self, event_body, props):
        logging.info("event body is %s" % event_body)
        logging.info("Properties are %s" % props)

The logging statements from run function are not coming to app insight which is connected to our azure functions. If I use normal function instead of async eventloop it push the logs to app insight.

Please let me know if more details required on this.

Thanks

[YunchuWang]

@amitnanaware thanks for raising this issue! We have investigated and root caused the problem. Essentially the host checks if invocation_id field (id generated by the host to identify each call to your function in function app.) is present in generated LogRecord object which wraps your log message, if yes then only it will log messages to AppInsights. For the missing logs you can’t find in AppInsights is because invocation_id field is missing in LogRecord objects of your log messages.

Currently for the case if a function is a single threaded blocking function, invocation id is only set to thread local variable(_invocation_id_local) in worker managed executor’s threads. (https://github.com/Azure/azure-functions-python-worker/blob/dev/azure_functions_worker/dispatcher.py#L644-L648). We do not set invocation_id to customer managed executor’s threads, and even trying to set it, that _invocation_id_local variable is not accessible outside worker module and is not considered good practice.

(more for details at https://github.com/Azure/azure-functions-python-worker/blob/dev/azure_functions_worker/dispatcher.py#L742-L754 and https://github.com/Azure/azure-functions-host/blob/dev/src/WebJobs.Script.Grpc/Channel/GrpcWorkerChannel.cs#L696-L732).

Unfortunately sorry, there is no quick mitigation at current moment. We are tracking it internally and will continue investigating/working on good solutions as soon as possible.

[hrichardlee]

@YunchuWang do you know if this issue has been fixed or is still outstanding? I’m seeing similar symptoms (logs from an async function in an Azure Function have no effect, logs on the main thread show up in Application Insights as expected)