Deploy an Azure Function with Cosmos DB Output Binding

Azure Functions is a serverless compute service that runs small units of code, called functions, in response to events without you managing any servers. Every function is defined by a trigger that starts it and, optionally, one or more bindings that connect it to other services. Bindings are the part that removes the most boilerplate: instead of writing SDK client code, opening connections, and handling retries yourself, you declare the service you want to talk to and the runtime wires it up for you at invocation time.

An output binding applies that idea to writing data. When a function declares a Cosmos DB output binding, the runtime reads a named application setting for the connection, targets a specific database and container, and persists whatever the function returns or assigns to the binding, without a single line of Cosmos SDK code in the function body. The binding is configured declaratively, either in function.json or, in the Node.js v4 programming model, inline in the function definition, which keeps the connection string out of source control and the persistence logic out of the handler. Azure Functions Core Tools is the local CLI that scaffolds this project structure and publishes it to a Function App in Azure.

Objectives

By completing this Intermediate challenge, you will be able to:

• Initialize a local Azure Functions project and scaffold an HTTP-triggered function with Azure Functions Core Tools.
• Configure a Cosmos DB output binding that targets a specific database and container.
• Reference a pre-configured application setting as the binding's connection rather than embedding credentials.
• Deploy a function project to an existing Function App running on a Flex Consumption plan.
• Invoke a deployed HTTP function and confirm the output binding persisted a document.

Prerequisites

Before attempting this challenge, you should be comfortable with:

• The Azure Functions trigger and binding model
• Basic JavaScript or Node.js
• Azure Cosmos DB for NoSQL concepts (account, database, container, partition key)
• Running commands in a terminal with the Azure CLI already authenticated