Explanation
Application Gateway currently has seven metrics to view performance counters.
Metrics are a feature for certain Azure resources where you can view performance counters in the portal. For Application Gateway, the following metrics are available:
* Total Requests
* Failed Requests
* Current Connections
* Healthy Host Count
* Response Status
* Throughput
* Unhealthy Host count
You can filter on a per backend pool basis to show healthy/unhealthy hosts in a specific backend pool References: https://docs.microsoft.com/en-us/azure/application-gateway/application-gatewaydiagnostics# Metrics