All error codes

server_not_stopped

HTTP 409 Server must be stopped for this operation

What happened

Changing the plan requires the server to be powered off, and this one is running. Cores, memory and the system disk are resized while the machine is down.

What to do

Stop the server with POST /v1/servers/{id}/actions/power-off, wait for the task to finish, then repeat the same request with the same idempotency key.

Retrying

Change the state this refers to, then repeat the same request with the same idempotency key.

How it arrives

{
    "type": "https://docs.fiberax.com/errors/server_not_stopped",
    "title": "Server must be stopped for this operation",
    "status": 409,
    "code": "server_not_stopped",
    "request_id": "a277dcd1ca652c65"
}

Branch your code on code, never on the wording of title.