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.
So, this 1 million request is for all your Azure Function app. So, there are metrics which are available to track the execution , so you need to write a script to capture that across all Azure function App and then check if that crosses > 4,00,000 GB-s.
You can use this PowerShell sample:
Get-AzMetric -ResourceId /subscriptions/<AZURE_SUBSCRIPTION_ID>/resourceGroups/metrics-testing-consumption/providers/Microsoft.Web/sites/metrics-testing-consumption -MetricName FunctionExecutionUnits,FunctionExecutionCount -AggregationType Total -TimeGrain 01:00:00 -StartTime 2019-09-11T21:46:00Z -EndTime 2019-09-11T23:18:00Z
Reference : https://learn.microsoft.com/en-us/azure/azure-functions/functions-consumption-costs?tabs=azure-powershell