Python Worker Extension Interface (worker)

[Hazhzeng]

Changes

1. Add ExtensionManager in extension.py which can be enabled by the feature flag PYTHON_ENABLE_WORKER_EXTENSIONS
2. Add trace_parent, trace_state and attributes replicating TraceParent, TraceState and Attributes values. This change will ensure the worker code is more Pythonic.
3. Improve logging in worker_init_request, now the log entry will include information like Python version, Worker version for ease of diagnostics.
   Received WorkerInitRequest, python version 3.7.5 (tags/v3.7.5:5c02a39a0b, Oct 15 2019, 00:11:34) [MSC v.1916 64 bit (AMD64)], worker version 1.1.10, request ID 768c03e6-b194-49ab-9866-0f9978fcdf1d
4. Add new Python Worker Extension logs for reporting registered Python Worker Extensions.
5. Add unit test cases in test_extension.py to validate worker extension implementation.

Description

This PR is based on #757

This PR has a dependency on Azure/azure-functions-python-library#81

This extension manager is intended to be used with azure.functions SDK. There're three roles involves in this scenarios.

1. Python function worker and SDK maintainers
2. Extension developers
3. Customers using Python Azure Functions

To enable this feature, two feature flags needs to be turned on in Python 3.6, 3.7 and 3.8.
Python 3.9 enables this feature by default.
PYTHON_ISOLATE_WORKER_DEPENDENCIES this will ensure when registering the extension, it will always direct to customer's azure-functions SDK instead of the built-in one.
PYTHON_ENABLE_WORKER_EXTENSIONS this will ensure the extension loaders are enabled. Otherwise, it will be ignored.

1. Python function worker and SDK maintainers

We decided to release a new extension module in azure.functions SDK where Extension developers can use it to register their extension. (Azure/azure-functions-python-library#81)

2. Extension developers

Here are two examples for developing Application Level Extension and Function Level Extension for Python Worker.
Function Extension: https://github.com/Hazhzeng/functions-ext-profile
Application Extension: https://github.com/Hazhzeng/application-ext-timer

3. Azure Functions Users

The need to download the extension and azure-functions in their requirements.txt

azure-functions
git+https://github.com/Hazhzeng/functions-ext-profile
git+https://github.com/Hazhzeng/application-ext-timer

To use a function extension:

import logging

import requests
import azure.functions as func
from functions_ext_profile import ProfileExtension

profile_extension = ProfileExtension(__file__)


def main(req: func.HttpRequest) -> func.HttpResponse:
    logging.info('Start Executing HttpFuncExt')
    requests.get('https://microsoft.com')
    # profile_extension.property
    return 'HttpFuncExt Executed: called https://microsoft.com'

To apply an application extension into every triggers:

import logging

import requests
import azure.functions as func

# Import application level extension
from application_ext_timer import TimerExtension


def main(req: func.HttpRequest) -> func.HttpResponse:
    logging.info('Start Executing HttpFuncExt')
    requests.get('https://xbox.com')
    return 'HttpAppExt Executed: called https://xbox.com'

Fixes #642
cc: @lzchen

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• New Unit tests were added for the changes made and CI is passing.

Quality of Code and Contribution Guidelines

• I have read the contribution guidelines.

[vrdmr]

An initial set of small comments.

[vrdmr]

The second set of comments. Still to finish the test_extension.py

[vrdmr]

LGTM;

minor comments.