Cosmos DB Document Updates

This is an example of updating Cosmos DB denormalized data using the change feed and Durable Azure Functions. The accompanying blog post can be found here.

Tooling

To run this repo you'll need to install

• .NET 8
• CosmosDB Emulator
• Azurite Storage Emulator

Settings

You'll also need to create a local.settings.json file in the directory root with the following data:

{
  "IsEncrypted": false,
  "Values": {
    "AzureWebJobsStorage": "UseDevelopmentStorage=true",
    "FUNCTIONS_WORKER_RUNTIME": "dotnet-isolated",
    "CosmosConnectionString": "AccountEndpoint=https://localhost:8081/;AccountKey=C2y6yDjf5/R+ob0N8A7Cgv30VRDJIWEHLM+4QDU5DE2nQ9nDuVTqobD4b8mGGyPMbIZnqyMsEcaGQy67XIw/Jw==",
    "DatabaseName": "Sales",
    "CustomerContainerName": "Customers",
    "OrderContainerName": "Orders"
  }
}

Cosmos Setup

In the Cosmos emulator, create a new database named Sales with two containers:

• Customers with a partition key of /id
• Orders with a partition key of /customerId

Create a few customers and orders with the following format:

{
    "id": "e81031a2-d8ab-43d0-a8ce-00ca81fa357b",
    "firstName": "Jeff",
    "lastName": "Jefferson"
}

{
    "id": "0548ab0e-3c2a-4d73-9e6c-261e32967b98",
    "customerId": "e81031a2-d8ab-43d0-a8ce-00ca81fa357b",
    "firstName": "Jeff",
    "lastName": "Jefferson",
    "subtotal": 82.31
}

Running

Start the Azurite emulator and the Cosmos DB emulator. To run the function app, run func start in the top level directory.