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nixos/switch-to-configuration: Document and test socket-activated services

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This commit is contained in:
Janne Heß 2022-02-25 14:32:44 +01:00
parent ad267cc9cf
commit 1def557525
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4 changed files with 169 additions and 20 deletions
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15
nixos/doc/manual/development/unit-handling.section.md
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@ -41,17 +41,18 @@ checks:
`RefuseManualStop` in the `[Unit]` section, and `X-OnlyManualStart` in the
`[Unit]` section.
- The rest of the behavior is decided whether the unit has `X-StopIfChanged`
in the `[Service]` section set (exposed via
- Further behavior depends on the unit having `X-StopIfChanged` in the
`[Service]` section set to `true` (exposed via
[systemd.services.\<name\>.stopIfChanged](#opt-systemd.services)). This is
set to `true` by default and must be explicitly turned off if not wanted.
If the flag is enabled, the unit is **stop**ped and then **start**ed. If
not, the unit is **restart**ed. The goal of the flag is to make sure that
the new unit never runs in the old environment which is still in place
before the activation script is run.
before the activation script is run. This behavior is different when the
service is socket-activated, as outlined in the following steps.
- The last thing that is taken into account is whether the unit is a service
and socket-activated. Due to a bug, this is currently only done when
`X-StopIfChanged` is set. If the unit is socket-activated, the socket is
stopped and started, and the service is stopped and to be started by socket
activation.
and socket-activated. If `X-StopIfChanged` is **not** set, the service
is **restart**ed with the others. If it is set, both the service and the
socket are **stop**ped and the socket is **start**ed, leaving socket
activation to start the service when it's needed.

22
nixos/doc/manual/from_md/development/unit-handling.section.xml
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@ -88,9 +88,10 @@
</listitem>
<listitem>
<para>
The rest of the behavior is decided whether the unit has
Further behavior depends on the unit having
<literal>X-StopIfChanged</literal> in the
<literal>[Service]</literal> section set (exposed via
<literal>[Service]</literal> section set to
<literal>true</literal> (exposed via
<link linkend="opt-systemd.services">systemd.services.&lt;name&gt;.stopIfChanged</link>).
This is set to <literal>true</literal> by default and must
be explicitly turned off if not wanted. If the flag is
@ -100,17 +101,22 @@
is <emphasis role="strong">restart</emphasis>ed. The goal of
the flag is to make sure that the new unit never runs in the
old environment which is still in place before the
activation script is run.
activation script is run. This behavior is different when
the service is socket-activated, as outlined in the
following steps.
</para>
</listitem>
<listitem>
<para>
The last thing that is taken into account is whether the
unit is a service and socket-activated. Due to a bug, this
is currently only done when
<literal>X-StopIfChanged</literal> is set. If the unit is
socket-activated, the socket is stopped and started, and the
service is stopped and to be started by socket activation.
unit is a service and socket-activated. If
<literal>X-StopIfChanged</literal> is
<emphasis role="strong">not</emphasis> set, the service is
<emphasis role="strong">restart</emphasis>ed with the
others. If it is set, both the service and the socket are
<emphasis role="strong">stop</emphasis>ped and the socket is
<emphasis role="strong">start</emphasis>ed, leaving socket
activation to start the service when it’s needed.
</para>
</listitem>
</itemizedlist>

9
nixos/modules/system/activation/switch-to-configuration.pl
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@ -307,6 +307,7 @@ sub handleModifiedUnit {
# seem to get applied on daemon-reload.
} elsif ($unit =~ /\.mount$/) {
# Reload the changed mount unit to force a remount.
# FIXME: only reload when Options= changed, restart otherwise
$unitsToReload->{$unit} = 1;
recordUnit($reloadListFile, $unit);
} elsif ($unit =~ /\.socket$/) {
@ -339,7 +340,7 @@ sub handleModifiedUnit {
# If this unit is socket-activated, then stop the
# socket unit(s) as well, and restart the
# socket(s) instead of the service.
my $socketActivated = 0;
my $socket_activated = 0;
if ($unit =~ /\.service$/) {
my @sockets = split(/ /, join(" ", @{$unitInfo{Service}{Sockets} // []}));
if (scalar @sockets == 0) {
@ -347,13 +348,15 @@ sub handleModifiedUnit {
}
foreach my $socket (@sockets) {
if (defined $activePrev->{$socket}) {
# We can now be sure this is a socket-activate unit
$unitsToStop->{$socket} = 1;
# Only restart sockets that actually
# exist in new configuration:
if (-e "$out/etc/systemd/system/$socket") {
$unitsToStart->{$socket} = 1;
recordUnit($startListFile, $socket);
$socketActivated = 1;
$socket_activated = 1;
}
# Remove from units to reload so we don't restart and reload
if ($unitsToReload->{$unit}) {
@ -368,7 +371,7 @@ sub handleModifiedUnit {
# that this unit needs to be started below.
# We write this to a file to ensure that the
# service gets restarted if we're interrupted.
if (!$socketActivated) {
if (!$socket_activated) {
$unitsToStart->{$unit} = 1;
recordUnit($startListFile, $unit);
}

143
nixos/tests/switch-test.nix
View File

@ -1,6 +1,46 @@
# Test configuration switching.
import ./make-test-python.nix ({ pkgs, ...} : {
import ./make-test-python.nix ({ pkgs, ...} : let
# Simple service that can either be socket-activated or that will
# listen on port 1234 if not socket-activated.
# A connection to the socket causes 'hello' to be written to the client.
socketTest = pkgs.writeScript "socket-test.py" /* python */ ''
#!${pkgs.python3}/bin/python3
from socketserver import TCPServer, StreamRequestHandler
import socket
import os
class Handler(StreamRequestHandler):
def handle(self):
self.wfile.write("hello".encode("utf-8"))
class Server(TCPServer):
def __init__(self, server_address, handler_cls):
listenFds = os.getenv('LISTEN_FDS')
if listenFds is None or int(listenFds) < 1:
print(f'Binding to {server_address}')
TCPServer.__init__(
self, server_address, handler_cls, bind_and_activate=True)
else:
TCPServer.__init__(
self, server_address, handler_cls, bind_and_activate=False)
# Override socket
print(f'Got activated by {os.getenv("LISTEN_FDNAMES")} '
f'with {listenFds} FDs')
self.socket = socket.fromfd(3, self.address_family,
self.socket_type)
if __name__ == "__main__":
server = Server(("localhost", 1234), Handler)
server.serve_forever()
'';
in {
name = "switch-test";
meta = with pkgs.lib.maintainers; {
maintainers = [ gleber das_j ];
@ -8,6 +48,7 @@ import ./make-test-python.nix ({ pkgs, ...} : {
nodes = {
machine = { pkgs, lib, ... }: {
environment.systemPackages = [ pkgs.socat ]; # for the socket activation stuff
users.mutableUsers = false;
specialisation = rec {
@ -231,6 +272,40 @@ import ./make-test-python.nix ({ pkgs, ...} : {
systemd.services.reload-triggers-and-restart.serviceConfig.X-Modified = "test";
};
simple-socket.configuration = {
systemd.services.socket-activated = {
description = "A socket-activated service";
stopIfChanged = lib.mkDefault false;
serviceConfig = {
ExecStart = socketTest;
ExecReload = "${pkgs.coreutils}/bin/true";
};
};
systemd.sockets.socket-activated = {
wantedBy = [ "sockets.target" ];
listenStreams = [ "/run/test.sock" ];
socketConfig.SocketMode = lib.mkDefault "0777";
};
};
simple-socket-service-modified.configuration = {
imports = [ simple-socket.configuration ];
systemd.services.socket-activated.serviceConfig.X-Test = "test";
};
simple-socket-stop-if-changed.configuration = {
imports = [ simple-socket.configuration ];
systemd.services.socket-activated.stopIfChanged = true;
};
simple-socket-stop-if-changed-and-reloadtrigger.configuration = {
imports = [ simple-socket.configuration ];
systemd.services.socket-activated = {
stopIfChanged = true;
reloadTriggers = [ "test" ];
};
};
mount.configuration = {
systemd.mounts = [
{
@ -676,7 +751,71 @@ import ./make-test-python.nix ({ pkgs, ...} : {
assert_contains(out, "would reload the following units: reload-triggers.service, simple-reload-service.service\n")
assert_contains(out, "would restart the following units: reload-triggers-and-restart-by-as.service, reload-triggers-and-restart.service, simple-restart-service.service, simple-service.service\n")
assert_lacks(out, "\nwould start the following units:")
assert_lacks(out, "as well:")
with subtest("socket-activated services"):
# Socket-activated services don't get started, just the socket
machine.fail("[ -S /run/test.sock ]")
out = switch_to_specialisation("${machine}", "simple-socket")
# assert_lacks(out, "stopping the following units:") nobody cares
assert_lacks(out, "NOT restarting the following changed units:")
assert_lacks(out, "reloading the following units:")
assert_lacks(out, "\nrestarting the following units:")
assert_lacks(out, "\nstarting the following units:")
assert_contains(out, "the following new units were started: socket-activated.socket\n")
machine.succeed("[ -S /run/test.sock ]")
# Changing a non-activated service does nothing
out = switch_to_specialisation("${machine}", "simple-socket-service-modified")
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:")
machine.succeed("[ -S /run/test.sock ]")
# The unit is properly activated when the socket is accessed
if machine.succeed("socat - UNIX-CONNECT:/run/test.sock") != "hello":
raise Exception("Socket was not properly activated") # idk how that would happen tbh
# Changing an activated service with stopIfChanged=false restarts the service
out = switch_to_specialisation("${machine}", "simple-socket")
assert_lacks(out, "stopping the following units:")
assert_lacks(out, "NOT restarting the following changed units:")
assert_lacks(out, "reloading the following units:")
assert_contains(out, "\nrestarting the following units: socket-activated.service\n")
assert_lacks(out, "\nstarting the following units:")
assert_lacks(out, "the following new units were started:")
machine.succeed("[ -S /run/test.sock ]")
# Socket-activation of the unit still works
if machine.succeed("socat - UNIX-CONNECT:/run/test.sock") != "hello":
raise Exception("Socket was not properly activated after the service was restarted")
# Changing an activated service with stopIfChanged=true stops the service and
# socket and starts the socket
out = switch_to_specialisation("${machine}", "simple-socket-stop-if-changed")
assert_contains(out, "stopping the following units: socket-activated.service, socket-activated.socket\n")
assert_lacks(out, "NOT restarting the following changed units:")
assert_lacks(out, "reloading the following units:")
assert_lacks(out, "\nrestarting the following units:")
assert_contains(out, "\nstarting the following units: socket-activated.socket\n")
assert_lacks(out, "the following new units were started:")
machine.succeed("[ -S /run/test.sock ]")
# Socket-activation of the unit still works
if machine.succeed("socat - UNIX-CONNECT:/run/test.sock") != "hello":
raise Exception("Socket was not properly activated after the service was restarted")
# Changing a reload trigger of a socket-activated unit only reloads it
out = switch_to_specialisation("${machine}", "simple-socket-stop-if-changed-and-reloadtrigger")
assert_lacks(out, "stopping the following units:")
assert_lacks(out, "NOT restarting the following changed units:")
assert_contains(out, "reloading the following units: socket-activated.service\n")
assert_lacks(out, "\nrestarting the following units:")
assert_lacks(out, "\nstarting the following units: socket-activated.socket")
assert_lacks(out, "the following new units were started:")
machine.succeed("[ -S /run/test.sock ]")
# Socket-activation of the unit still works
if machine.succeed("socat - UNIX-CONNECT:/run/test.sock") != "hello":
raise Exception("Socket was not properly activated after the service was restarted")
with subtest("mounts"):
switch_to_specialisation("${machine}", "mount")