What is Azure Functions runtime version settings and daily usage quota(GB-Sec)

In the Azure Functions App, we have Function runtime settings which contains two settings

Azure functions supports 3 versions of runtime host 1.x, 2.x and 3.x.  Azure Function Runtime is a specific version runtime where your function app runs on top of it. Once you develop and deploy the function app with a specific runtime host it shows runtime version values (relevant values are ~1, ~2  or ~3) in Runtime version. 

To understand more on application settings refer http://www.dotnetmirror.com/articles/microsoft-azure/234/how-to-add-or-update-app-settings-in-azure-functions-from-portal

{
   "name": "FUNCTIONS_EXTENSION_VERSION",
   "value": "~3",
   "slotSetting": false
 }

Note: If you are changing runtime value 3 to  1, you will get a message as “Your app is currently running version ~3 and has existing functions. Switching to version ~1 is not recommended since it can introduce breaking changes to languages and bindings. Are you sure you want to continue?” Before you change runtime setting, make sure your app and code is working.

Fig : Azure Functions runtime settings

To understand bit more on Azure Functions Runtime refer http://www.dotnetmirror.com/articles/microsoft-azure/228/what-is-azure-functions-runtime

The other option we have under Function runtime settings is Daily Usage Quota which is useful if you are running your Function in consumption plan. Your function app pricing depends on the amount of memory you consume. By setting daily usage quota, your function app will be stopped until the next day at 0:00AM UTC once it reaches the defined limit.

Azure Functions consumption plan is billed based on per-second resource consumption and executions.  Consumption plan pricing includes a monthly free grant of 1 million requests and 4,00,000 GB-s of resource consumption per month per subscription in pay-as-you-go pricing across all function apps in that subscription.