Azure Functions Node.js Stream Sample

The app in this repo streams a large file (96mb by default) named input.txt to a file output.txt and logs the progress.

Prerequsites

• Version 4.0.5530 of Azure Functions Core Tools
• Node.js v18+

Run the app

1. Add a local.settings.json file with the following contents:

   {
       "IsEncrypted": false,
       "Values": {
           "AzureWebJobsStorage": "",
           "FUNCTIONS_WORKER_RUNTIME": "node",
           "FUNCTIONS_REQUEST_BODY_SIZE_LIMIT": "4294967296"
       }
   }

2. Run npm install.

3. Run npm start. This will build the app, create the large input file, and start the app.

4. Leave the previous terminal running and open a new terminal to execute a function.

   • If you want to simulate streaming a request, run npm run streamRequest.
   • If you want to simulate streaming a response, run npm run streamResponse.

5. You should see progress in the console as the file is processed. It happens fast for a 96mb file, but as long as you see a chunk count greater than 1, you know your data was streamed.

App contents

• src/functions/*: The actual functions for your app
• src/scripts/*: Scripts used to create the large file and send requests to Azure Functions
• src/constants.ts: A file with several settings that you can change to modify the behavior of the app.

Next steps

1. If you want to make it even more fun, change the value of fileSize in src/constants.ts to a larger value (the max as defined in local.settings.json above is 4 GB).
2. If you haven't already, read our blog post for this feature.