services	platforms	author
app-service, functions	nodejs	ityer

On-demand calculation of Azure consumption cost

This code sample demonstrates how to use Azure billing commerce APIs to find consumption cost per subscription and resource-group. We will use an Azure Function to execute the code.

The challenge

The Billing API and the Consumption API don't expose the cost of the consumption. Instead they only expose the ability to interact with past invoices (which is not service an on-demand need), or receive consumption quantities without cost.

For example, you will be able to tell that some subscription had 5 compute hours, but the cost is not present, nor the price per compute unit.

In addition, some functions are also not available for sponsored accounts.

Explaining the solution

Azure Commerce APIs provides 2 functions:

1. Resource usage. This will give you consumption data for an Azure subscription.
2. Resource RateCard. This will give price and metadata information for resources used in an Azure subscription. It contains mainly a price for each meter.

This solution simply ties all the edges to calculate the actual cost under a single wrapper.

There are 4 steps to extract the cost:

1. Authenticate to Azure and obtain the Credentials object.
2. Use the Credentials object to pull rateCards which are the rates set up for the given account. Rate are also called Meters.
3. Use the Credentials object to pull Consumption data for each resource in the given subscription. Each consumption listing contains the Meter ID from the rate cards. Consumption provides you with a quantity per meterID.
4. The last step is to multiply the rate value with the consumption quantity. This is the cost.

Results can be filtered by resource group or resource tags. The Node.js code makes use of the Azure node.js SDKs.

Deploy the sample to Azure

The automated deployment provisions an Azure Storage account and an Azure Function in a Dynamic compute plan and sets up deployment from source control.

When you setup the Azure Function, you will be requested to supply information and credentials to initialize the function. This is a one time step. Make sure you have in hand:

Name	Type	Description
clientId	string	Your service principal ID
clientSecret	string	Your service principal secret
tenantId	string	Your subscription tenant ID
subscriptionId	string	Subscription ID to pull consumption info for
offerId	string	Must be specific code taken from Microsoft Azure Offer Details

The deployment template has a parameter manualIntegration which controls whether or not a deployment trigger is registered with GitHub. Use true if you are deploying from the main Azure-Samples repo (does not register hook), false otherwise (registers hook). Since a value of false registers the deployment hook with GitHub, deployment will fail if you don't have write permissions to the repo. Iy you want to deploy it from your own repo, make sure your account is authorized GitHub.com, otherwise, it will fail with authentication error.

Calling the function

Once the template is deployed, 2 functions will be created:

1. get-consumption-cost-node: The function will use the provided credentials and parameters to login into Azure, pull both Rate and Consumption data and calculate the actual cost, based on the rates and consumption.
2. download-consumtion-cost: The function will use the provided credentials and parameters to login into Azure, pull both Rate and Consumption data and calculate a detailed report of the actual cost of each resource, based on the rates and consumption. The result is a csv files which can be downloaded from the function.

Optional parameters:

Name	Type	Description
detailed	bool	true if the consumption info should contain details. Optional. relevant only for get-consumption-cost-node
filter	string	A way to limit results only to a specific resource instance info. For example: resource group, tags etc. Optional.
startDate	Date	Start time for the report. The date format is ECMAScript YYYY-MM-DDTHH:mm:ss.sssZ . Optional. Defaults to 24 hours ago
endDate	Date	End time for the report. The date format is ECMAScript YYYY-MM-DDTHH:mm:ss.sssZ. Optional. Defaults to now.
granularity	string	Can be: "Daily" or "Hourly". Optional. Default is Daily.

The paramaters are sent as json in the body of the POST request.

Calling the function

Example of calling the function:

curl -H "Content-Type: application/json" -X POST -d '{"filter":"resource-group-name","detailed":"true"}' https://<function-name>.azurewebsites.net/api/get-consumption-cost-node?code=<code>

If the function will be called from a mobile client or a JavaScript web app, we recommend that you add authentication to your Function using App Service Authentication/Authorization. The API key is usually insufficent for security purposes since it can be discovered by sniffing traffic or decompiling the client app.

The function will take a considerate amount of seconds to execute, because it performs 3 API calls: Login, Get Rates, Get Consumption. A real-world scenario will use caching/sessions to avoid multiple logins and Get rates.

The response

Is an object in the form of:

{ total: (Number, the total cost), details: (Key-Value pairs of resource and cost)}

For example:

{ total: 10.3, details: { res1:5, res2: 5.3}}

Learn more

• Authentication and authorization in Azure App Service