Understand Azure Functions app settings

  • 4 minutes

As a Tailwind Traders engineer, you're working on an API that connects to a database. Your API will connect to that database via a database connection string. In this module, you'll learn best practices for storing sensitive information like connection strings in an Azure Functions API.

Store connection strings as app setting

It's a good idea to avoid hard-coding connection strings. You'll likely use the connection string across different files, and there's a chance that it could change in the future.

You'll want to store the connection string as an app setting:

  • App settings are specified in one place and referenced throughout the app.
  • You can easily change them at any point in the future without having to change the code.
  • App settings are never checked in to source control.

An Azure Functions project has a local.settings.json file. This file contains a set of key/value pairs the app uses as configuration values when developing locally. You can add your own items to the Values object. You can access those values from your code.

{
  "IsEncrypted": false,
  "Values": {
    "AzureWebJobsStorage": "",
    "FUNCTIONS_WORKER_RUNTIME": "node",
    "AzureWebJobsFeatureFlags": "EnableWorkerIndexing"
  }
}

If you want to add a connection string, you can add another property called "CONNECTION_STRING" (or whatever you'd like to call it), and then pass the connection string to your database.

{
  "IsEncrypted": false,
  "Values": {
    "AzureWebJobsStorage": "",
    "FUNCTIONS_WORKER_RUNTIME": "node",
    "AzureWebJobsFeatureFlags": "EnableWorkerIndexing",
     "CONNECTION_STRING": "AccountEndpoint=https://tailwind-traders-7071.documents.azure.com:443/;AccountKey=123456;"
  }
}

Access app settings in Azure Functions code

To access these configuration values in your Azure Functions from JavaScript, use the process.env object. It contains all of the key/value pairs that are specified in the local.settings.json file.

The following code found at ./api/src/services/product.services.ts reads the connection string from the process.env object to create the CosmosClient object to access the Azure Cosmos DB service.

let client = new CosmosClient(process.env.CONNECTION_STRING);

You now know how to securely store a connection string during local development, and how to reference that string in your application.