{"id":10713,"date":"2025-07-11T10:30:15","date_gmt":"2025-07-11T17:30:15","guid":{"rendered":"https:\/\/devblogs.microsoft.com\/cosmosdb\/?p=10713"},"modified":"2025-07-11T10:30:15","modified_gmt":"2025-07-11T17:30:15","slug":"building-event-driven-go-applications-with-azure-cosmos-db-and-azure-functions","status":"publish","type":"post","link":"https:\/\/devblogs.microsoft.com\/cosmosdb\/building-event-driven-go-applications-with-azure-cosmos-db-and-azure-functions\/","title":{"rendered":"Building Event-Driven Go applications with Azure Cosmos DB and Azure Functions"},"content":{"rendered":"

The Go programming language<\/a>\u00a0is a great fit for building serverless applications. Go applications can be easily compiled to a single, statically linked binary, making deployment simple and reducing external dependencies. They start up quickly, which is ideal for serverless environments where functions are frequently invoked from a cold start. Go applications also tend to use less memory compared to other languages, helping optimize resource usage and reduce costs in serverless scenarios.<\/p>\n

Azure Functions supports Go using\u00a0custom handlers<\/a>, and you can use triggers and input and output bindings via extension bundles. Azure Functions is\u00a0tightly integrated with Azure Cosmos DB<\/a>\u00a0using bindings (input<\/a>,\u00a0output<\/a>), and\u00a0triggers<\/a>.<\/p>\n

This blog post will walk you through how to build Azure Functions with Go that make use of these Azure Cosmos DB integrations. Bindings allow you to easily read and write data to Azure Cosmos DB, while triggers are useful for building event-driven applications that respond to changes in your data in Azure Cosmos DB.<\/p>\n

Part 1<\/strong>\u00a0of this blog starts off with a function that gets triggered by changes in a Azure Cosmos DB container and simply logs the raw Azure Functions event payload and the Cosmos DB document. You will learn how to run the function and also test it with Cosmos DB locally, thanks to the\u00a0Azure Cosmos DB emulator<\/a>\u00a0and\u00a0Azure Functions Core Tools<\/a>. If this is your first time working with Go and Azure Functions, you should find it helpful to get up and running quickly. Although you can deploy it to Azure, we will save that for the next part of this blog.<\/p>\n

Part 2<\/strong>\u00a0dives into another function that generates embeddings for the documents in the Azure Cosmos DB container. This example will use an\u00a0Azure OpenAI<\/a>\u00a0embedding model to generate embeddings for the documents in the container and then store the embeddings back in the container. This is useful for building applications that require semantic search or other generative AI applications.<\/p>\n

Check out the\u00a0GitHub repository<\/a>\u00a0for the complete code.<\/div><\/p>\n

Part 1: Build a simple Azure Cosmos DB trigger-based function and run it locally<\/h2>\n

Just as the Azure Cosmos DB emulator lets you run Azure Cosmos DB locally, Azure Functions Core Tools lets you develop and test your functions locally.<\/p>\n

Start by installing the Azure Functions Core Tools \u2013\u00a0refer to the documentation<\/a>\u00a0for instructions for your OS. For example, on Linux, you can:<\/p>\n

sudo apt-get update\r\nsudo apt-get install azure-functions-core-tools-4<\/code><\/pre>\n
Next, start the Azure Cosmos DB emulator. The commands below are for Linux and use the Docker container-based approach –\u00a0refer to the documentation<\/a>\u00a0for other options.<\/p>\n
You need to have Docker installed and running on your machine. If you don’t have it installed, please refer to the Docker installation guide<\/a>.<\/div><\/p>\n
docker pull mcr.microsoft.com\/cosmosdb\/linux\/azure-cosmos-emulator:latest\r\n\r\ndocker run \\\r\n --publish 8081:8081 \\\r\n --name linux-emulator \\\r\n -e AZURE_COSMOS_EMULATOR_PARTITION_COUNT=1 \\\r\n mcr.microsoft.com\/cosmosdb\/linux\/azure-cosmos-emulator:latest<\/code><\/pre>\n
Make sure to\u00a0configure the emulator SSL certificate as well<\/a>. For example, for the Linux system I was using, I ran the following command to download the certificate and regenerate the certificate bundle:<\/p>\n
\n
curl --insecure https:\/\/localhost:8081\/_explorer\/emulator.pem > ~\/emulatorcert.crt\r\n\r\nsudo update-ca-certificates<\/code><\/pre>\n
Use the following URL to navigate to the Azure Cosmos DB Data Explorer using your browser:\u00a0http:\/\/localhost:8081\/_explorer\/index.html<\/code>. Create the following resources:<\/p>\n