Dear Fujii-san, Zhihong,
I attached the latest version.
The biggest change is that callbacks are no longer un-registered at the end of transactions.
FDW developer must enable or disable timeout instead, via new APIs.
The timer will be turned on when:
* new GUC is >= 0, and
* anyone calls TryEnableRemoteServerCheckingTimeout().
I think this version is reduced overhead, but it might not be developer friendly...
Best Regards,
Hayato Kuroda
FUJITSU LIMITED