Azure Application Gateway Current Connections
I have noticed unusual behavior, related to Current Connection metrics, between the Azure Application Gateway V1 SKU and the V2 SKU.
Under the V1 SKU, gateway connections remained low in comparison to the total number of requests. By comparison, under the V2 SKU, gateway connections are substantially higher than the total number of requests, and exhibits this continued growth, then sudden drop.
This behavior is illustrated by comparing the two graphs below. I'll note that the application behind the gateway did not change in any way. Is anyone able to offer insight into why we're seeing this behaviour?
V1 Gateway -- the orange line is Current Connections (sum), and the purple line is the Total Requests (sum).
V2 Gateway -- the orange line is Current Connections (sum), and the purple line is the Total Requests (sum).
I engaged the Microsoft team who were able to identify this issue as a bug within the latest version of the V2 application gateway. This bug resulted in abnormal reporting of the connections metric.
In my case, they advised that they rolled back the version of our V2 application gateway, and I presume are working on a permanent fix in the meantime.
This resulted in connection metrics being reported correctly by the gateway (orange line below is the connections -- note the immediate drop and the return to nominal values once the rollback occurred).
Should you happen to encounter this issue within your own application gateways, I encourage you to submit a support ticket.