All error codes

ip_in_use

HTTP 409 IP address is attached to a server

What happened

The public IP address is attached to a server. You either asked to release it, or asked to put it on a new interface while another server still holds it.

What to do

Detach the address first - move that interface to a private network, delete the interface, or delete the server holding it - and then repeat the same request. Detaching happens inside the task that call returns, and the address leaves the server a few seconds before that task turns terminal: wait for the task (or poll GET /v1/ips until the address shows server_id null) and only then release. A release sent while that task is still running answers this same 409.

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/ip_in_use",
    "title": "IP address is attached to a server",
    "status": 409,
    "code": "ip_in_use",
    "request_id": "a277dcd1ca652c65"
}

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