[Elastic Agent] Prevent a second agent from starting.

[ph]

Prevent a second instance of the Agent from running to reduce the problems of collision in the configuration or race in the configuration on disk

[elasticmachine]

Pinging @elastic/ingest-management (Team:Ingest Management)

[ph]

cc @EricDavisX

[EricDavisX]

what is the actual desired behavior if / when this is attempted? Perhaps the behavior should be to un-install the existing agent and then install the new / current agent? I don't know ramifications.

[blakerouse]

@ph I think with #18021 we can easily prevent multiple from running. Being that the GRPC server will be open on a specific port or socket. We can verify that if its already in use then to not start.

[ph]

@blakerouse I think we might need mot than that, I was considering adding an flock on the data folder to make sure only one process can read the file in it. This would prever two agents running on different port accessing the same files.

[blakerouse]

@ph okay I can work on adding the flock

[ruflin]

Is a flock something that is supported cross platform?

[blakerouse]

Seems github.com/gofrs/flock supports both unix and windows, so should be. libbeat already uses that module in its libbeat/cmd/instance/locker.go.

[ph]

@blakerouse sound good., I believe we use it for the exact same thing or even the persisted queue.