AgentToServer aggregatable capabilities

[RassK]

Background

Some agents cannot perform restarts and package upgrades themselves, which means there must be a supervisor.
Agents with integrated OpAmp client can connect directly or via a supervisor to a backend, which creates a conflict in capabilities depending on whether the agent is directly connected or connected via a supervisor.

The capabilities in question are:
AgentCapabilities.AcceptsRestartCommand
AgentCapabilities.AcceptsPackages

Possible solutions

AgentCapabilities.AcceptsRestartCommand seems easy to handle. I think in 99% of cases, the supervisor doesn't need to consult the agent to determine, if it can perform restart or not. So the agent always reports missing the capability and the supervisor adds this capability when relaying the message to the backend.

AgentCapabilities.AcceptsPackages seems quite tricky. Usually, there is a global installation which you can possibly update using a supervisor. On the other hand, it's possible that the agent is integrated into a customer's application at build time (like using a NuGet package), which definitely is not upgradable. Now the agent must indicate that the package is locked and not upgradable, so the supervisor is not going to add the capability.

These cases can be solved by custom capabilities in my mind (even though "capability" seems like an incorrect word for this). I'm just wondering if such standard cases can be more clearly defined... or does anybody have better opinions?

[tigrannajaryan]

I am not sure I fully understand what this is about. You are describing a scenario where the Agent reports its capability to the Supervisor and the Supervisor needs to decide which of the capabilities to forward as-is and which ones to override. Is that the question?

[RassK]

I am not sure I fully understand what this is about. You are describing a scenario where the Agent reports its capability to the Supervisor and the Supervisor needs to decide which of the capabilities to forward as-is and which ones to override. Is that the question?

This part is correct, in case there is a supervisor.

[tigrannajaryan]

I don't see what we need in the spec for this. This seems to be a particular concern of some Supervisors and some Agents and how they interact together. Yes, the Supervisor needs to make a decision about whether AcceptsPackages capability reporting by the Agent is what the Supervisor wants to report to the Server as is or it wants to override it. I think this is very application/environment-specific decision. I am not sure we can have anything about this in the spec.

[RassK]

Possibly requires flags like "requires supervisor for restart", "requires supervisor for packages", "downstream client is supervisor". If those are present then direct OpAMP server communication knows to aggregate that if restarts and package updates are possible or not.