[Feature Request] Support Subscription Discovery mechanism similar to Target Discovery

[vuthinh0301]

Description

Currently, gnmic supports dynamic Target Discovery (via file, consul, docker, k8s, etc.), which allows targets to be added or removed automatically. However, Subscriptions are still static and require a full instance restart or manual configuration changes whenever we need to update what paths or features we want to subscribe to.

In a dynamic infrastructure, subscription requirements change frequently. Forcing a restart of gnmic just to update subscriptions introduces operational risks and causes data gaps for other active targets.

Expected Behavior / Proposal

I would like to propose a Subscription Discovery feature, similar to how Target Discovery works:

• Dynamic Loading: gnmic could watch a directory, a file, or a key-value store for subscription configurations.
• Hot Reload/Update: When a new subscription is defined or an existing one is modified/deleted via the discovery source, gnmic should dynamically apply the changes to the relevant targets without restarting the entire process.

This enhancement would make subscription management as flexible and cloud-native as target management. Thank you for considering this feature!

[karimra]

If you use the collector mode gnmic collector instead of subscribe command gnmic subscribe, you will be able to modify targets, subscriptions, outputs and inputs via the REST API.

[Wyrtrorm]

Hi @karimra,

Thanks for your explanation, this sounds very useful. I just have one pending question about this new "collector" mode: is there any way to make the data persistent? I mean, if a restart occurs, is there any way to keep all the changes that were made through the API?
This mode pretty much closes the topic of "dynamic" targets/subscriptions/outputs/..., but from what I understand, it loses persistence of that data in the process.
If needed, I'm happy to open a dedicated and detailed issue about this.

Thanks for your work :)

[karimra]

It's not possible today but you can use https://operator.gnmic.dev if you are ok running Kubernetes.
You get instance lifecycle and persistence for free.