Feature Request: select @@vtgate_hostname; support

[serhatcetinkaya]

Feature Description

Hello, I previously opened #17246 and continued discussion with @harshit-gangal in the community slack. The common decision was to create a feature request for it.

This is a feature request to have some mechanism to run select @@vtgate_hostname; or select @@vtgate_id; from the client and retrieving hostname/host id of the vtgate on the other end of the connection.

Use Case(s)

For the following use case on our side this would be very helpful and save us hours of debugging:

We have our application deployed in 3 different AZ's, similarly vtgate is also deployed in 3 different AZ's and application creates connection to vtgate over a layer 4 load balancer. Rarely we see increased database latency metrics on subset of the application instances. After hours of debugging we figured out requests from one specific AZ to another one had an intermittent issue on cloud provider side and this was the reason. If we'd known which application instance is connected to which vtgate in advance, we could have quickly notice the latency pattern.