lechnerc77 / follow_along_func_custom_handlers

Following along the Video Serverless Go in Azure Functions with custom handlers

Serverless Go in Azure Functions with custom handlers

This repository contains kind of a transcript for the YouTube video Serverless Go in Azure Functions with custom handlers by Anthony Chu. The video contains a lot of helpful information about custom handlers and beyond. This repository contains the code for the single steps Anthony is executing in his video. Each step is represented in an own branch. The corresponding starting point of the video is referenced accordingly in the sections describing the branch.

Prerequisites

The complete tutorial is build in WSL2 on Windows10 to mimic the non-Windows environment of the original video. I used the Ubuntu 20.04 image. Beside having WSL2 running you also need some further things to be installed in WSL2:

• Go via apt i.e.sudo apt-get install golang.
• Node e.g. installed via NVM (Node version manager) as described here
• Azurite as storage emulator installed via npm. I also created a dedicated location for storing the data in ~/azurite_store.
• VS Code Azure Function Extension
• VS Code Azure Storage Extension

You should also install the Azure Storage Explorer on your Windows host. This can directly access Azurite via port-forwarding from WSL2.

Remark

As the local.settings.json file is usually not committed I created a placeholder file called local.settings sample.json that can serve as a template.

Walk Through

Setting up the Go Server

YouTube Reference: Link

Branch: main

Hints:

• Do not forget to build the go file.
• Ports are forwarded from WSL2, so you can directly access the endpoints from your Windows host.

Transforming the Server to an Azure Function

YouTube Reference: Link

Branch: function_custom_handler

Hints:

• Set the defaultExecutablePath to server in the host.json for the custom handler- no server.exe as we are on Linux.
• Add the parameter enableForwardingHttpRequest and set it to true.
• Adopt the server.go to fetch the port from the environment variable FUNCTIONS_CUSTOMHANDLER_PORT.
• Do not forget to build the go file.

Adding a Queue Trigger

YouTube Reference: Link

Branch: queue_trigger

Hints:

• Create a new function with a queue trigger.
• Adopt the server.go file to handle a new route. See code for details.
• Do not forget to build the go file.
• Do not forget to set the AzureWebJobsStorage parameter to UseDevelopmentStorage=true; in the local.settings.json file.
• Do not forget to launch Azurite before starting the function via azurite --silent --location ~/azurite_store.

Deploying to Azure

YouTube Reference: Link

Branch: cross_compile

Hints:

• As deployment is done to a Windows app on Azure we need to cross-compile the app. The relevant statement is available in the file crosscompile.sh.
• Do not forget to execute chmod +x on the file to make it executable.
• Do not forget to set the defaultExecutablePath to server.exe in the host.json.
• In order to be able to proceed with the local scenario, we override the setting in host.json the setting in the local.settings.json via setting teh parameter AzureFunctionsJobHost__customHandler__description__defaultExecutablePath to the value server (Remark: This can be done with any parameter in host.json using the parameter path separated by __).

Routing (aka catch all route)

YouTube Reference: Link

Branch: routing

Hints:

• Adopt the go file and do not forget to register a new generic route.
• Do not forget to build the go file.
• Rename the function to all.
• Add the route property to the function.json file for the all function and set it to a wildcard.

Debug

YouTube Reference: Link

Branch: debug

Hints:

• Add the property logLevel to host.json and set it to { "default": "Trace" } in order to get an extensive log output in your console.