Since 9.5, you could use cluster_name for this purpose.
> S. Bob <mailto:sbob(at)quadratum-braccas(dot)com>
> Monday, February 18, 2019 12:08 PM
> Hi all;
>
>
> Does PostgreSQL store a unique cluster or instance identifier that we
> can access to identify our instances?
>
>
> Thanks in advance
>
>