[erlang-questions] Future of epmd

Per Hedeland per@REDACTED
Wed Nov 7 20:15:54 CET 2012

Dmitry Demeshchuk <demeshchuk@REDACTED> wrote:
>1. When we send ALIVE2_REQ and reply with ALIVE2_RESP, we establish a TCP
>connection. Closing of which is a signal of node disconnection. This
>approach does have a point, since we can use keep-alive and periodically
>check that the node is still here on the TCP level.

No, the point is rather the opposite - since this is always a local
loopback connection, epmd is guaranteed (by the OS/kernel) to
"immediately" find out that the erlang node died (or disconnected), by
means of socket close (EOF) - no matter how the death came about. TCP
keep-alives, that by necessity incur a delay (and the default is
typically huge) before detection of a problem, are not only inferior but
pointless in this scenario.

--Per Hedeland

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