Update subscriptions in a similar fashion to Targets Discovery mechanism

[zerogvt]

Hello 👋

gNMIc is a great project! Thanks a mil for sharing and supporting it!

I'm in the process of adopting it as part of a statistics NMI pipeline. So far it works great and it is very promising. Only thing that I'm not sure I get right is the next use case:

Say that subscriptions need to change over the course of time. E.g. imagine I need to get stats on dropped packets on installed filters. Imagine that these filters might come and go all the time due to a management system constantly adjusting the routers. In this case I'll need to keep updating my subscriptions so that they are in sync with the filter names.

It would be great if that could be done via a mechanism similar to the targets discovery, i.e. if gNMIc could get these updates and remove obsolete subscriptions and add new subscriptions on the fly.

Atm it seems I'll need to get the subscription updates from my backend, insert them in the configuration file and restart the gNMIc cluster which can be done but it is a bit cumbersome and deviates from the targets discovery workflow.

It'd be great if you got it into the roadmap somewhere if you see value in it.

Anyhow, thanks again!

Best