Application gateway error 502

Question

I have set up a new Application Gateway by following the documentation. I have configured the backend pool and connected it to an App Service via FQDN. But, somehow I receive error 502 every time I browse to the gateway. Browsing to the website directly works without issues .

Answer 1

You need to set up the health probes via ARM templates or using PowerShelI as they cannot be setup through Azure Portal if you have web apps in your backend pools. You need to leave the host field empty and set -PickHostNameFromBackendAddress property.

This code snippet should resolve your error:

# Create a probe with the PickHostNameFromBackendHttpSettings switch for web apps
$probeconfig = New-AzureRmApplicationGatewayProbeConfig -name webappprobe -Protocol Http -Path / -Interval 30 -Timeout 120 -UnhealthyThreshold 3 -PickHostNameFromBackendHttpSettings    

# Define the backend http settings
$poolSetting = New-AzureRmApplicationGatewayBackendHttpSettings -Name appGatewayBackendHttpSettings -Port 80 -Protocol Http -CookieBasedAffinity Disabled -RequestTimeout 120 -PickHostNameFromBackendAddress -Probe $probeconfig