Debugging Azure Functions locally can be a daunting task, but with the right tools and mindset, you can streamline your workflow and get back to coding.
To start debugging Azure Functions locally, you'll need to install the Azure Functions Core Tools, which can be done via npm or yarn.
The Azure Functions Core Tools provide a command-line interface to create, run, and debug Azure Functions locally, making it easier to identify and fix issues.
Having the right tools in place can save you a significant amount of time and frustration in the long run.
Setting Up Local Environment
To set up a local environment for debugging Azure Functions, you'll want to choose a development environment that suits your language and tooling preferences. You can use Visual Studio Code, the command prompt or terminal, Visual Studio, or Maven (for Java development).
For Visual Studio Code, the Azure Functions extension adds Functions support, and you'll need the Core Tools to get started. This environment supports development on Linux, macOS, and Windows, using version 2.x of the Core Tools.
The command prompt or terminal is another option, which provides the core runtime and templates for creating functions, enabling local development. Version 2.x supports development on Linux, macOS, and Windows, relying on the Core Tools for the local Functions runtime.
Visual Studio is also a viable choice, with the Azure Functions tools included in the Azure development workload, starting with Visual Studio 2019. This environment lets you compile functions in a class library and publish the .dll to Azure, including the Core Tools for local testing.
For Java development, Maven archetype supports Core Tools, enabling development of Java functions, and version 2.x supports development on Linux, macOS, and Windows.
Here are the local development environments you can choose from:
Remember, you should develop your functions locally and publish your code project to a function app in Azure, due to limitations on editing function code in the Azure portal.
Debugging Azure Functions
Debugging Azure Functions can be a bit tricky, but don't worry, I've got you covered. To debug an Azure Function from Visual Studio, you'll need to replicate the configuration from your Azure App Service using a local JSON file. This will likely involve making some adjustments to the values.
You'll also need to set up an Azure Storage account, but you can use an installed emulator instead of a real account when running locally. The emulator will impact the values in your configuration, so make sure to get that set up first.
Once you have your configuration and storage in place, you can debug your Azure Function from Visual Studio by setting the function project as the startup project for your solution.
You can also debug Azure Functions locally using VS Code and the Azure Functions extension. This process involves putting a breakpoint in your code, running your function from the CLI with the --debug flag, and then hitting F5 or going to the Debug tab and pressing Play.
To debug a JavaScript function using the CLI and Visual Studio Code, you'll need to:
1. Put a breakpoint in your code
2. Run your function from the CLI with the --debug flag
3. Hit F5 or go to the Debug tab and press Play
4. Make a request to your function's local URL
5. Your breakpoint will be hit and you can use all of VS Code's debugging capabilities
Here are some general steps for debugging Azure Functions locally:
- Use Visual Studio Code
- Install the Azure Functions extension
- Install the Azure Functions Core Tools
- Install Azurite
- Install the Azure Storage Explorer
Note that debugging C# functions in Visual Studio Code requires the OmniSharp extension and some extra configuration, while debugging C# functions in Visual Studio is generally easier.
Local Development Tools
Local development tools are essential for debugging Azure Functions locally. You can use Visual Studio Code, the Command Prompt or Terminal, Visual Studio, Maven (for Java), or even the Azure portal to develop and test your functions.
To develop Azure Functions locally, you need to install the Azure Functions Core Tools, which enables an integrated local debugging experience. This can be done by running the Azure Functions: Install or Update Azure Functions Core Tools command from the command pallet in Visual Studio Code.
Here are some of the local development environments that support Azure Functions development:
Each of these environments uses the Core Tools for local testing and debugging.
Local Development Environments
Local development environments are a crucial part of building and testing Azure Functions. You can develop functions on your local computer using various tools and languages.
Visual Studio Code is a popular choice for local development, supporting languages like C#, JavaScript, PowerShell, and Python. The Azure Functions extension for VS Code adds Functions support, requiring the Core Tools for local development. You can install the Core Tools by running the Azure Functions: Install or Update Azure Functions Core Tools command from the command pallet.
Command prompt or terminal is another option for local development, supporting the same languages as VS Code. The Azure Functions Core Tools provide the core runtime and templates for creating functions, enabling local development on Linux, macOS, and Windows.
Visual Studio is also a viable option for local development, with the Azure Functions tools included in the Azure development workload starting with Visual Studio 2019. This allows you to compile functions in a class library and publish the .dll to Azure.
Maven is a Java-based development environment that supports local development of Azure Functions using the Core Tools. Version 2.x of the Core Tools supports development on Linux, macOS, and Windows.
Here's a table summarizing the local development environments supported by Azure Functions:
Each of these environments lets you create function app projects and use predefined function templates to create new functions. They all use the Core Tools to test and debug your functions against the real Functions runtime on your own machine.
Local Storage Emulator
You can use the local Azurite emulator to test Azure Storage bindings without connecting to remote storage services. Azurite integrates with Visual Studio Code and Visual Studio, and you can also run it from the command prompt using npm.
To use Azurite, you need to have it installed and running. You should also test with an actual storage connection to Azure services before publishing to Azure.
To configure the project for local development, set the Values.AzureWebJobsStorage key to a valid Azure Storage account connection string. You can also use the Azurite emulator by setting the value of AzureWebJobsStorage to UseDevelopmentStorage=true.
Here are the steps to set the storage account connection string:
- In the Azure portal, navigate to your storage account.
- In the Access keys tab, below Security + networking, copy the Connection string of key1.
- In your project, open the local.settings.json file and set the value of the AzureWebJobsStorage key to the connection string you copied.
- Repeat the previous step to add unique keys to the Values array for any other connections required by your functions.
The Azure Storage Emulator is a Windows-only tool that simulates blob, queue, and table storage. You can install it via the Visual Studio installer or download a standalone installer from the official Microsoft documentation.
To connect the Function to the Emulator, replace the AzureWebJobsStorage connection string with “UseDevelopmentStorage=true”. The Emulator will automatically start when the project is run in Visual Studio.
Configure for Local Development
To configure your Azure Function for local development, you'll need to set up an Azure Storage account connection string. This is required for all trigger types other than HTTP and webhooks. The connection string can be obtained from the Azure portal by navigating to your storage account, clicking on the Access keys tab, and copying the Connection string of key1.
To add the connection string to your project, open the local.settings.json file and set the value of the AzureWebJobsStorage key to the connection string you copied. You'll also need to repeat this step to add unique keys to the Values array for any other connections required by your functions.
Here's a step-by-step guide to setting up the storage account connection string:
1. In the Azure portal, navigate to your storage account.
2. In the Access keys tab, below Security + networking, copy the Connection string of key1.
3. In your project, open the local.settings.json file and set the value of the AzureWebJobsStorage key to the connection string you copied.
4. Repeat the previous step to add unique keys to the Values array for any other connections required by your functions.
By following these steps, you'll be able to configure your Azure Function for local development and ensure that your functions can access the necessary storage resources.
Running and Executing Functions
Running Azure Functions locally is a great way to test and debug your code without deploying it to the cloud. You can use the Azure Functions extension in VS Code to run your functions locally.
There are a few ways to run your functions locally, but one of the most straightforward methods is to use the Azure Functions Core Tools. These tools let you run your Azure Functions project on your local development computer, and they're usually installed automatically when you start a function from Visual Studio.
To start your function in Visual Studio in debug mode, simply press F5. If prompted, accept the request to download and install the Azure Functions Core (CLI) tools, and make sure to enable any necessary firewall exceptions.
Here's a step-by-step guide to running your function in debug mode:
- Press F5 in Visual Studio.
- Accept the request to download and install the Azure Functions Core (CLI) tools.
- Enable any necessary firewall exceptions.
Once your function is running, you can test it as you would a deployed function. Breakpoints will be hit as expected, and you can use all of VS Code's debugging capabilities.
You can also use the CLI to run your function in debug mode, which is especially useful if you're working on a project that uses the JavaScript language. To do this, put a breakpoint in your code, run your function from the CLI with the --debug flag, and then make a request to your function's local URL. Your breakpoint will be hit, and you can start debugging.
Triggers and Bindings
To debug Azure functions locally, you need to consider trigger and binding behaviors. Triggers and bindings are essential components of Azure functions, and understanding how they work is crucial for local development.
You can test HTTP triggers by calling the HTTP endpoint on your local computer using http://localhost/. This is the easiest way to test HTTP triggers.
For non-HTTP triggered functions, there are several options to run locally. You can use connection strings that target live Azure services by adding the appropriate connection string settings in the Values array in the local.settings.json file. However, this approach impacts live service data, so it's recommended to set up separate services for development and testing.
Here are some options to run non-HTTP triggered functions locally:
- Use a local storage emulator for storage-based triggers.
- Manually run non-HTTP trigger functions using special administrator endpoints.
To manually run a non-HTTP triggered function, you need to use the special administrator endpoint provided by Core Tools. For more information, see Manually run a non HTTP-triggered function.
During local testing, you must be running the host provided by Core Tools (func.exe) locally. For more information, see Azure Functions Core Tools.
Sources
- https://learn.microsoft.com/en-us/azure/azure-functions/functions-develop-local
- https://thwack.solarwinds.com/groups/devops/b/blog/posts/debug-and-run-azure-functions-locally
- https://mfblog.au/p/running-azure-functions-locally/
- https://www.sharepointnutsandbolts.com/2018/10/Azure-Functions-Visual-Studio-Code-CLI.html
- https://learn.microsoft.com/en-us/azure/azure-functions/functions-develop-vs
Featured Images: pexels.com