Remote Agent shutdown and/or pause capability

[djaglowski]

A "shutdown" capability can be useful for retiring unsupported versions / zombie instances.

Is it assumed that the OpAMP connection is lost after the "shutdown"? This would mean "shutdown" is irreversible (unless the Agent us run again after e.g. machine restarts)?

That is how I would define it.

I have implemented a shutdown in a supervised model but not one where the supervisor had a connection. I'll describe that first as a possible model:

• Server sends a shutdown signal to the agent
• The agent process shuts down w/ a particular exit code
• The supervisor checks the exit code and interprets it to mean that it should itself shut down
• If there is an externally driven restart (e.g. machine restart)
  • The agent connects to the server, transmits (among other things) its ID
  • The server recognizes the ID as having been retired, and responds with another "shutdown" signal

In the case where the supervisor has a connection, it may worth differentiating between the cases where a total shutdown is desired, vs waiting for further instructions. Even a standalone agent could differentiate between the two behaviors:

• "shutdown": end the process
• "pause": cease all activity except for the connection to server

Originally posted by @djaglowski in #22 (comment)

[andykellr]

I proposed an implementation in open-telemetry/opamp-go#53 using ServerToAgent.Flags