/
service-order.nix
61 lines (60 loc) · 1.49 KB
/
service-order.nix
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# Ordering Services
#
# Given a set of services, make them run one at a time in a specific
# order, on a timer.
{ lib, ... }:
{
# Given a list of systemd service, give each one an After
# attribute, so they start in a specific order. The returned
# list can be converted in to a systemd.services attrset with
# `lib.listToAttrs`.
#
# Example:
#
# mkOrderedChain [
# { name = "foo"; value = { script = "true"; }; }
# { name = "bar"; value = { script = "true"; }; }
# ]
#
# => [
# {
# name = "foo";
# value = {
# script = "true";
# unitConfig = { After = []; };
# };
# }
# {
# name = "bar";
# value = {
# script = "true";
# unitConfig = { After = [ "bar" ]; };
# };
# }
#
mkOrderedChain = jobs: let
unitConfigFrom = job: job.unitConfig or {};
afterFrom = job: (unitConfigFrom job).After or [];
previousFrom = collector:
if collector ? previous
then [collector.previous]
else [];
ordered = builtins.foldl'
(collector: item: {
services = collector.services
++ [{
inherit (item) name;
value = item.value // {
unitConfig = (unitConfigFrom item.value) //
{
After = (afterFrom item.value) ++
(previousFrom collector);
};
};
}];
previous = item.name;
})
{ services = []; }
jobs;
in ordered.services;
}