epmd: Introduce erlang port mapper daemon service #43812
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Also I've addressed @peterhoeg comments from #34265 in this PR |
GrahamcOfBorg
added
6.topic: erlang
6.topic: nixos
peterhoeg
reviewed
Jul 19, 2018
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Apart from one tiny thing, this is great! |
added 2 commits
July 19, 2018 17:32
That way 'epmd' can be started by systemd using socket activation. This is important to have when there is more than one Erlang system used on the same host. Support for this exists since 17.0: erlang/otp@b7c95ea Configure flag was added in 17.1: erlang/otp@12cd5e5
Having socket-activated epmd means that there always be only a single instance managed centrally. Because Erlang also starts it automatically if not available, and in worst case scenario 'epmd' can be started by some Erlang application running under systemd. And then restarting this application unit will cause complete loss of names in 'epmd' (if other Erlang system are also installed on this host). E.g. see at which lengths RabbitMQ goes to recover from such situations: https://github.com/rabbitmq/rabbitmq-server/blame/7741b37b1efa97ac9b17685cc626bd35ee52ca16/src/rabbit_epmd_monitor.erl#L36 Having the only one socket-activated epmd completely solves this problem.
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Hi @peterhoeg. I've removed |
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Motivation for this change
Having socket-activated epmd means that there always be only a single instance managed centrally. Because Erlang also starts it automatically if not available, and in worst case scenario 'epmd' can
be started by some Erlang application running under systemd. And then restarting this application unit will cause complete loss of names in 'epmd' (if other Erlang system are also installed on this host).
E.g. see at which lengths RabbitMQ goes to recover from such situations:
https://github.com/rabbitmq/rabbitmq-server/blame/7741b37b1efa97ac9b17685cc626bd35ee52ca16/src/rabbit_epmd_monitor.erl#L36
Having the only one socket-activated epmd completely solves this problem.
Things done
sandboxinnix.confon non-NixOS)nix-shell -p nox --run "nox-review wip"./result/bin/)nix path-info -Sbefore and after)