Heartbeat between Primary and Standby replicas

Hello everyone,

I am designing a heartbeat system between replicas to know when a replica
goes down so that necessary measures can be taken. As I see, there are two
ways of doing it:

1) Creating a separate heartbeat process on replicas.
2) Creating a heartbeat message, and sending it over the connection that is
already established between walsender and walreceiver.

With 2, sending heartbeat from walsender to walreceiver seems trivial.
Sending a heartbeat from walreceiver to walsender seems tricky. Going
through the code, it seems that the walreceiver is always in the
PGASYNC_COPY_OUT mode (except in the beginning when handshaking is done).

Can you recommend the right way of doing this?

Thank you.

Regards

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Postgres version = 9.0 beta-4