https://github.com/notheotherben/azfn-customhandler-otel

https://github.com/notheotherben/azfn-customhandler-otel

Last synced: 8 days ago
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• Host: GitHub
• URL: https://github.com/notheotherben/azfn-customhandler-otel
• Owner: notheotherben
• Created: 2023-10-23T21:51:24.000Z (about 1 year ago)
• Default Branch: main
• Last Pushed: 2023-10-24T09:10:40.000Z (about 1 year ago)
• Last Synced: 2024-11-09T02:34:07.203Z (2 months ago)
• Language: Go
• Size: 2.93 KB
• Stars: 0
• Watchers: 1
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md

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README

        
# Azure Functions Custom Handler OpenTelemetry Repro

This repository contains an extremely simple Azure Function app which leverages the

["HTTP-only" custom handler][httponly] model and demonstrates that there is a problem with

OpenTelemetry trace context propagation in the production Azure Functions runtime

when AppInsights is disabled.

This project is currently deployed at 

should you wish to validate the behaviour without deploying your own function.

## Requirements

You will need [Go](https://go.dev) installed on your machine, as well as the Azure Functions

Core Tools. Once you have these, you will be able to build the application and deploy it (or

test it locally).

**NOTE**: I'm building and running this on Windows (both local dev and Azure Functions OS).

## Deploy to Azure

When deploying to Azure, you can confirm this behaviour by enabling/disabling the AppInsights

integration on the function app. When AppInsights is enabled, the trace context is propagated

correctly, while when it is disabled, the trace context is not propagated (i.e. it will show ``).

```bash

# Build the main handler executable

go build main.go

# Upload the function to Azure (note that you will need to have created the function app before doing this)

func azure functionapp publish $FUNCTION_APP_NAME

# Invoke the function

curl https://$FUNCTION_APP_NAME.azurewebsites.net/api/hello

# You should see the following output (while this issue remains unpatched):

# Hello World, your OpenTelemetry TraceParent is: 

```

## Test Locally

When testing locally, you should build the project for your local platform and then start it using the

`func start` command. Note that you may need to update the `host.json` file to match the name of the

handler executable (`main` on Linux/MacOS systems and `main.exe` on Windows systems).

```bash

# Build the main handler executable for your local platform

go build main.go

# Start the local function app

func start

# Invoke the function

curl http://localhost:7071/api/hello

# You should see the following output:

# Hello World, your OpenTelemetry TraceParent is: 00-f70e7847ea52af240e5efff633e57cd5-baf07326de5b0eda-00

```

[httponly]: https://learn.microsoft.com/en-us/azure/azure-functions/functions-custom-handlers#http-only-function