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nixos/switch-to-configuration: Ignore some unit keys

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Some unit keys don't need to restart the service to make them effective.
Reduce the amount of service restarts by ignoring these keys
This commit is contained in:
Janne Heß 2022-03-06 19:22:04 +01:00
parent acb535fb61
commit c96180c53f
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GPG Key ID: 69165158F05265DF
4 changed files with 71 additions and 18 deletions
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3
nixos/doc/manual/development/unit-handling.section.md
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@ -17,7 +17,8 @@ checks:
them and comparing their contents. If they are different but only
`X-Reload-Triggers` in the `[Unit]` section is changed, **reload** the unit.
The NixOS module system allows setting these triggers with the option
[systemd.services.\<name\>.reloadTriggers](#opt-systemd.services). If the
[systemd.services.\<name\>.reloadTriggers](#opt-systemd.services). There are
some additional keys in the `[Unit]` section that are ignored as well. If the
unit files differ in any way, the following actions are performed:
- `.path` and `.slice` units are ignored. There is no need to restart them

5
nixos/doc/manual/from_md/development/unit-handling.section.xml
View File

@ -38,8 +38,9 @@
<emphasis role="strong">reload</emphasis> the unit. The NixOS
module system allows setting these triggers with the option
<link linkend="opt-systemd.services">systemd.services.&lt;name&gt;.reloadTriggers</link>.
If the unit files differ in any way, the following actions are
performed:
There are some additional keys in the <literal>[Unit]</literal>
section that are ignored as well. If the unit files differ in
any way, the following actions are performed:
</para>
<itemizedlist>
<listitem>

67
nixos/modules/system/activation/switch-to-configuration.pl
View File

@ -226,10 +226,20 @@ sub unrecord_unit {
sub compare_units {
my ($old_unit, $new_unit) = @_;
my $ret = 0;
# Keys to ignore in the [Unit] section
my %unit_section_ignores = map { $_ => 1 } qw(
X-Reload-Triggers
Description Documentation
OnFailure OnSuccess OnFailureJobMode
IgnoreOnIsolate StopWhenUnneeded
RefuseManualStart RefuseManualStop
AllowIsolate CollectMode
SourcePath
);
my $comp_array = sub {
my ($a, $b) = @_;
return join("\0", @{$a}) eq join("\0", @{$b});
return join("\0", @{$a}) eq join "\0", @{$b};
};
# Comparison hash for the sections
@ -238,6 +248,18 @@ sub compare_units {
foreach my $section_name (keys %{$old_unit}) {
# Missing section in the new unit?
if (not exists $section_cmp{$section_name}) {
# If the [Unit] section was removed, make sure that only keys
# were in it that are ignored
if ($section_name eq 'Unit') {
foreach my $ini_key (keys %{$old_unit->{'Unit'}}) {
if (not defined $unit_section_ignores{$ini_key}) {
return 1;
}
}
next; # check the next section
} else {
return 1;
}
if ($section_name eq 'Unit' and %{$old_unit->{'Unit'}} == 1 and defined(%{$old_unit->{'Unit'}}{'X-Reload-Triggers'})) {
# If a new [Unit] section was removed that only contained X-Reload-Triggers,
# do nothing.
@ -255,8 +277,8 @@ sub compare_units {
my @old_value = @{$old_unit->{$section_name}{$ini_key}};
# If the key is missing in the new unit, they are different...
if (not $new_unit->{$section_name}{$ini_key}) {
# ... unless the key that is now missing was the reload trigger
if ($section_name eq 'Unit' and $ini_key eq 'X-Reload-Triggers') {
# ... unless the key that is now missing is one of the ignored keys
if ($section_name eq 'Unit' and defined $unit_section_ignores{$ini_key}) {
next;
}
return 1;
@ -264,19 +286,30 @@ sub compare_units {
my @new_value = @{$new_unit->{$section_name}{$ini_key}};
# If the contents are different, the units are different
if (not $comp_array->(\@old_value, \@new_value)) {
# Check if only the reload triggers changed
if ($section_name eq 'Unit' and $ini_key eq 'X-Reload-Triggers') {
$ret = 2;
} else {
return 1;
# Check if only the reload triggers changed or one of the ignored keys
if ($section_name eq 'Unit') {
if ($ini_key eq 'X-Reload-Triggers') {
$ret = 2;
next;
} elsif (defined $unit_section_ignores{$ini_key}) {
next;
}
}
return 1;
}
}
# A key was introduced that was missing in the old unit
if (%ini_cmp) {
if ($section_name eq 'Unit' and %ini_cmp == 1 and defined($ini_cmp{'X-Reload-Triggers'})) {
# If the newly introduced key was the reload triggers, reload the unit
$ret = 2;
if ($section_name eq 'Unit') {
foreach my $ini_key (keys %ini_cmp) {
if ($ini_key eq 'X-Reload-Triggers') {
$ret = 2;
} elsif (defined $unit_section_ignores{$ini_key}) {
next;
} else {
return 1;
}
}
} else {
return 1;
}
@ -284,10 +317,14 @@ sub compare_units {
}
# A section was introduced that was missing in the old unit
if (%section_cmp) {
if (%section_cmp == 1 and defined($section_cmp{'Unit'}) and %{$new_unit->{'Unit'}} == 1 and defined(%{$new_unit->{'Unit'}}{'X-Reload-Triggers'})) {
# If a new [Unit] section was introduced that only contains X-Reload-Triggers,
# reload instead of restarting
$ret = 2;
if (%section_cmp == 1 and defined $section_cmp{'Unit'}) {
foreach my $ini_key (keys %{$new_unit->{'Unit'}}) {
if (not defined $unit_section_ignores{$ini_key}) {
return 1;
} elsif ($ini_key eq 'X-Reload-Triggers') {
$ret = 2;
}
}
} else {
return 1;
}

14
nixos/tests/switch-test.nix
View File

@ -64,6 +64,11 @@ in {
};
};
simpleServiceDifferentDescription.configuration = {
imports = [ simpleService.configuration ];
systemd.services.test.description = "Test unit";
};
simpleServiceModified.configuration = {
imports = [ simpleService.configuration ];
systemd.services.test.serviceConfig.X-Test = true;
@ -497,6 +502,15 @@ in {
assert_lacks(out, "\nstarting the following units:")
assert_lacks(out, "the following new units were started:")
# Only changing the description does nothing
out = switch_to_specialisation("${machine}", "simpleServiceDifferentDescription")
assert_lacks(out, "stopping the following units:")
assert_lacks(out, "NOT restarting the following changed units:")
assert_lacks(out, "reloading the following units:")
assert_lacks(out, "\nrestarting the following units:")
assert_lacks(out, "\nstarting the following units:")
assert_lacks(out, "the following new units were started:")
# Restart the simple service
out = switch_to_specialisation("${machine}", "simpleServiceModified")
assert_contains(out, "stopping the following units: test.service\n")