Azure Application Gateway: Deregistering Instances

Question

Is using Remove-AzApplicationGatewayBackendAddressPool and removing completely the instance from the backend-pool the only way to explicitly deregister an instance?

Isn't there something similar to other gateways where you disable it but not remove it from the pool?

I know you can deregister with a custom health probe but I need to do it explicitly since according to Microsoft:

Connection draining helps you achieve graceful removal of backend pool members during planned service updates. This setting is enabled via the backend http setting and can be applied to all members of a backend pool during rule creation. Once enabled, Application Gateway ensures all deregistering instances of a backend pool don't receive any new request while allowing existing requests to complete within a configured time limit. This applies to both backend instances that are explicitly removed from the backend pool by a user configuration change, and backend instances that are reported as unhealthy as determined by the health probes. The only exception to this are requests bound for deregistering instances, which have been deregistered explicitly, because of gateway-managed session affinity and continues to be proxied to the deregistering instances.

You can only keep drain connections while keeping session affinity by explicitly deregistering the instance. That is, after the instance is deregistered the users with sessions in the instance that was deregistered must continue the connection to that instance.

Thanks.

Answer 1

Hi @TS-FW ,

We currently do not have an option for deregistering backend pool instances except to manually fail the probe on the server itself or remove it from the backend pool

I can understand that you have a requirement for it and it would be great if you can share this as feedback on https://feedback.azure.com/forums/217313-networking so that users can upvote it. The feedbacks are regularly reviewed by the Product Group team and taken into consideration for the next feature developement provided there's enough upvotes.

Hope this helps. Do feel free to let me know if there's anything else i can assist you with.

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