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nixos/lix: prepare for socket activation changes

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After [1], nix-daemon will be socket-activated, and the service options need to
be set on the template unit. In the meantime, it does approximately nothing and
is harmless.

[1] https://gerrit.lix.systems/c/lix/+/4719
This commit is contained in:
Alois Wohlschlager
2025-12-14 15:53:41 +01:00
parent a6c7a5b4b5
commit d82e12e0dd
1 changed files with 65 additions and 52 deletions
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nixos/modules/programs/lix.nix
+65 -52
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@@ -10,6 +10,26 @@ let
nixPackage = cfg.package.out;
commonNixDaemonConfig = {
path = [
nixPackage
config.programs.ssh.package
];
environment =
cfg.envVars
// {
CURL_CA_BUNDLE = config.security.pki.caBundle;
}
// config.networking.proxy.envVars;
serviceConfig = {
CPUSchedulingPolicy = cfg.daemonCPUSchedPolicy;
IOSchedulingClass = cfg.daemonIOSchedClass;
IOSchedulingPriority = cfg.daemonIOSchedPriority;
};
};
makeNixBuildUser = nr: {
name = "nixbld${toString nr}";
value = {
@@ -39,61 +59,54 @@ in
systemd.sockets.nix-daemon.wantedBy = [ "sockets.target" ];
systemd.services.nix-daemon = {
path = [
nixPackage
config.programs.ssh.package
];
systemd.services."nix-daemon@" = lib.mkMerge [
commonNixDaemonConfig
{
# Do not kill connections serving established connections on upgrade.
restartIfChanged = false;
}
];
environment =
cfg.envVars
// {
CURL_CA_BUNDLE = config.security.pki.caBundle;
}
// config.networking.proxy.envVars;
systemd.services.nix-daemon = lib.mkMerge [
commonNixDaemonConfig
{
restartTriggers = [ config.environment.etc."nix/nix.conf".source ];
serviceConfig = {
CPUSchedulingPolicy = cfg.daemonCPUSchedPolicy;
IOSchedulingClass = cfg.daemonIOSchedClass;
IOSchedulingPriority = cfg.daemonIOSchedPriority;
};
# `stopIfChanged = false` changes to switch behavior
# from stop -> update units -> start
# to update units -> restart
#
# The `stopIfChanged` setting therefore controls a trade-off between a
# more predictable lifecycle, which runs the correct "version" of
# the `ExecStop` line, and on the other hand the availability of
# sockets during the switch, as the effectiveness of the stop operation
# depends on the socket being stopped as well.
#
# As `nix-daemon.service` does not make use of `ExecStop`, we prefer
# to keep the socket up and available. This is important for machines
# that run Nix-based services, such as automated build, test, and deploy
# services, that expect the daemon socket to be available at all times.
#
# Notably, the Nix client does not retry on failure to connect to the
# daemon socket, and the in-process RemoteStore instance will disable
# itself. This makes retries infeasible even for services that are
# aware of the issue. Failure to connect can affect not only new client
# processes, but also new RemoteStore instances in existing processes,
# as well as existing RemoteStore instances that have not saturated
# their connection pool.
#
# Also note that `stopIfChanged = true` does not kill existing
# connection handling daemons, as one might wish to happen before a
# breaking Nix upgrade (which is rare). The daemon forks that handle
# the individual connections split off into their own sessions, causing
# them not to be stopped by systemd.
# If a Nix upgrade does require all existing daemon processes to stop,
# nix-daemon must do so on its own accord, and only when the new version
# starts and detects that Nix's persistent state needs an upgrade.
stopIfChanged = false;
restartTriggers = [ config.environment.etc."nix/nix.conf".source ];
# `stopIfChanged = false` changes to switch behavior
# from stop -> update units -> start
# to update units -> restart
#
# The `stopIfChanged` setting therefore controls a trade-off between a
# more predictable lifecycle, which runs the correct "version" of
# the `ExecStop` line, and on the other hand the availability of
# sockets during the switch, as the effectiveness of the stop operation
# depends on the socket being stopped as well.
#
# As `nix-daemon.service` does not make use of `ExecStop`, we prefer
# to keep the socket up and available. This is important for machines
# that run Nix-based services, such as automated build, test, and deploy
# services, that expect the daemon socket to be available at all times.
#
# Notably, the Nix client does not retry on failure to connect to the
# daemon socket, and the in-process RemoteStore instance will disable
# itself. This makes retries infeasible even for services that are
# aware of the issue. Failure to connect can affect not only new client
# processes, but also new RemoteStore instances in existing processes,
# as well as existing RemoteStore instances that have not saturated
# their connection pool.
#
# Also note that `stopIfChanged = true` does not kill existing
# connection handling daemons, as one might wish to happen before a
# breaking Nix upgrade (which is rare). The daemon forks that handle
# the individual connections split off into their own sessions, causing
# them not to be stopped by systemd.
# If a Nix upgrade does require all existing daemon processes to stop,
# nix-daemon must do so on its own accord, and only when the new version
# starts and detects that Nix's persistent state needs an upgrade.
stopIfChanged = false;
};
}
];
# Set up the environment variables for running Nix.
environment.sessionVariables = cfg.envVars;