Re: [RFC V1 6/6] migration: cpr-transfer mode

[Steven Sistare]

On 6/30/2024 3:44 PM, Steve Sistare wrote:
> Add the cpr-transfer migration mode.  Usage:
[...]
> @@ -2144,6 +2158,29 @@ void qmp_migrate(const char *uri, bool has_channels,
>           goto out;
>       }
>   
> +    /*
> +     * For cpr-transfer mode, the target first reads CPR state, which cannot
> +     * complete until cpr_state_save above finishes, then the target creates
> +     * the migration channel and listens.  We must wait for the channel to
> +     * be created before connecting to it.
> +     *
> +     * This implementation of waiting is a hack.  It restricts the channel
> +     * type, and will loop forever if the target dies.  It should be defined
> +     * as a main-loop event that calls connect on the back end.
> +     */
> +    if (s->parameters.mode == MIG_MODE_CPR_TRANSFER) {
> +        SocketAddress *saddr = &addr->u.socket;
> +        if (addr->transport == MIGRATION_ADDRESS_TYPE_SOCKET &&
> +            saddr->type == SOCKET_ADDRESS_TYPE_UNIX) {
> +            while (access(saddr->u.fd.str, F_OK)) {
> +                usleep(1000000);
> +            }

I now have a proper fix for this handshake in my work space.

- Steve