[systemd-devel] After= and Wants= doesn't seem to have an effect

[Christopher Wong]

I think the temperature-controller.service is stopped due to the Before=temperature-controller.service in coco-wiper-manager.service.


There are no BindsTo=

The Conflicts=shutdown.target only.


I will do some more investigations after New Year.


Thank you for your time and explanations!


Merry X'mas and Happy New Year!

Christopher Wong

________________________________
From: Anita Zhang <the.anitazha at gmail.com>
Sent: Thursday, December 23, 2021 9:21:48 AM
To: Christopher Wong
Cc: systemd-devel at lists.freedesktop.org
Subject: Re: [systemd-devel] After= and Wants= doesn't seem to have an effect

I think the telling part is "temperature-controller.service/start finished, result=canceled". When another job for the same unit comes in (e.g. "temperature-controller.service: Trying to enqueue job temperature-controller.service/stop/replace") then the first job gets canceled and replaced by the new one (this is the default behavior which I think can be overridden). The bad part is systemd doesn't have logs to tell you why the stop transaction was issued. Maybe you can use `systemctl show temperature-controller.service` to see if there are BindsTo= or Conflicts= dependencies that are not listed in the unit files and causing the stop job to get issued.

As for your other point about why opticsd.service runs after temperature-controller.service's stop job, I think this is by design. According to https://github.com/systemd/systemd/blob/4d484e14bb9864cef1d124885e625f33bf31e91c/src/core/job.c#L1659-L1698 if  "b" starts after "a", but "a" has a stop job queued, then "a" will stop, then "b" will start. Substitute opticsd for "b" and temperature-controller for "a". The Wants= property issued a start job so what you're expecting is "a" starts, then "b" starts. But due to the canceled job mentioned above, you're instead left with "a" stops, then "b" starts.

Hope that helps,
Anita

On Wed, Dec 22, 2021 at 10:15 AM Christopher Wong <Christopher.Wong at axis.com<mailto:Christopher.Wong at axis.com>> wrote:

The code is being run on systemd 247.6. I finally got some debug logs to share (see below). The starting of opticsd.service is held back, waiting for temperature-controller.service, which is good. However, the line right after: Job 721, which is a stop job for temperature-controller finished with result=done. That seems to trigger the continuation of opticsd.service. I don't have the logs for when Job 107 was started and why Job 721 is created. My guess is that temperature-controller is waiting for coco-wiper-manager as indicated in Job 722 and Job 809. Could this really be a bug and I am that lucky to stumble into it?


Dec 22 18:03:17 axis-b8a44f278c56 systemd[1]: Got message type=method_call sender=n/a destination=org.freedesktop.systemd1 path=/org/freedesktop/systemd1 interface=org.freedesktop.systemd1.Manager member=StopUnit cookie=1 reply_cookie=0 signature=ss error-name=n/a error-message=n/a
Dec 22 18:03:17 axis-b8a44f278c56 systemd[1]: temperature-controller.service: Trying to enqueue job temperature-controller.service/stop/replace
Dec 22 18:03:17 axis-b8a44f278c56 systemd[1]: Added job temperature-controller.service/stop to transaction.
Dec 22 18:03:17 axis-b8a44f278c56 systemd[1]: temperature-controller.service: Job 107 temperature-controller.service/start finished, result=canceled
Dec 22 18:03:17 axis-b8a44f278c56 systemd[1]: Sent message type=signal sender=org.freedesktop.systemd1 destination=n/a path=/org/freedesktop/systemd1 interface=org.freedesktop.systemd1.Manager member=JobRemoved cookie=1 reply_cookie=0 signature=uoss error-name=n/a error-message=n/a
Dec 22 18:03:17 axis-b8a44f278c56 systemd[1]: temperature-controller.service: Installed new job temperature-controller.service/stop as 721
Dec 22 18:03:17 axis-b8a44f278c56 systemd[1]: temperature-controller.service: Enqueued job temperature-controller.service/stop as 721
Dec 22 18:03:17 axis-b8a44f278c56 systemd[1]: Sent message type=signal sender=org.freedesktop.systemd1 destination=n/a path=/org/freedesktop/systemd1/unit/temperature_2dcontroller_2eservice interface=org.freedesktop.DBus.Properties member=PropertiesChanged cookie=2 reply_cookie=0 signature=sa{sv}as error-name=n/a error-message=n/a
Dec 22 18:03:17 axis-b8a44f278c56 systemd[1]: Sent message type=signal sender=org.freedesktop.systemd1 destination=n/a path=/org/freedesktop/systemd1/unit/temperature_2dcontroller_2eservice interface=org.freedesktop.DBus.Properties member=PropertiesChanged cookie=3 reply_cookie=0 signature=sa{sv}as error-name=n/a error-message=n/a
Dec 22 18:03:17 axis-b8a44f278c56 systemd[1]: Sent message type=signal sender=org.freedesktop.systemd1 destination=n/a path=/org/freedesktop/systemd1 interface=org.freedesktop.systemd1.Manager member=JobNew cookie=4 reply_cookie=0 signature=uos error-name=n/a error-message=n/a
Dec 22 18:03:17 axis-b8a44f278c56 systemd[1]: Sent message type=method_return sender=org.freedesktop.systemd1 destination=n/a path=n/a interface=n/a member=n/a cookie=5 reply_cookie=1 signature=o error-name=n/a error-message=n/a
Dec 22 18:03:17 axis-b8a44f278c56 systemd[1]: opticsd.service: starting held back, waiting for: temperature-controller.service
Dec 22 18:03:17 axis-b8a44f278c56 systemd[1]: temperature-controller.service: Job 721 temperature-controller.service/stop finished, result=done
Dec 22 18:03:17 axis-b8a44f278c56 systemd[1]: Sent message type=signal sender=org.freedesktop.systemd1 destination=n/a path=/org/freedesktop/systemd1 interface=org.freedesktop.systemd1.Manager member=JobRemoved cookie=6 reply_cookie=0 signature=uoss error-name=n/a error-message=n/a
Dec 22 18:03:17 axis-b8a44f278c56 systemd[1]: Failed to read pids.max attribute of cgroup root, ignoring: No data available
Dec 22 18:03:17 axis-b8a44f278c56 systemd[1]: opticsd.service: Forked /usr/bin/udevadm as 561
Dec 22 18:03:17 axis-b8a44f278c56 systemd[1]: Sent message type=signal sender=org.freedesktop.systemd1 destination=n/a path=/org/freedesktop/systemd1/unit/opticsd_2eservice interface=org.freedesktop.DBus.Properties member=PropertiesChanged cookie=7 reply_cookie=0 signature=sa{sv}as error-name=n/a error-message=n/a
Dec 22 18:03:17 axis-b8a44f278c56 systemd[1]: Sent message type=signal sender=org.freedesktop.systemd1 destination=n/a path=/org/freedesktop/systemd1/unit/opticsd_2eservice interface=org.freedesktop.DBus.Properties member=PropertiesChanged cookie=8 reply_cookie=0 signature=sa{sv}as error-name=n/a error-message=n/a
Dec 22 18:03:17 axis-b8a44f278c56 systemd[1]: opticsd.service: Changed dead -> start-pre
Dec 22 18:03:17 axis-b8a44f278c56 systemd[1]: Starting Optics daemon...
...


Dec 22 18:03:17 axis-b8a44f278c56 systemd[1]: Keeping job coco-wiper-manager.service/start because of temperature-controller.service/start
Dec 22 18:03:17 axis-b8a44f278c56 systemd[1]: temperature-controller.service: Installed new job temperature-controller.service/start as 722
Dec 22 18:03:17 axis-b8a44f278c56 systemd[1]: temperature-controller.service: Enqueued job temperature-controller.service/start as 722
Dec 22 18:03:17 axis-b8a44f278c56 systemd[1]: temperature-controller.service: starting held back, waiting for: coco-wiper-manager.service
Dec 22 18:03:17 axis-b8a44f278c56 systemd[1]: temperature-controller.service: Trying to enqueue job temperature-controller.service/stop/replace
Dec 22 18:03:17 axis-b8a44f278c56 systemd[1]: Added job temperature-controller.service/stop to transaction.
Dec 22 18:03:17 axis-b8a44f278c56 systemd[1]: temperature-controller.service: Job 722 temperature-controller.service/start finished, result=canceled
Dec 22 18:03:17 axis-b8a44f278c56 systemd[1]: temperature-controller.service: Installed new job temperature-controller.service/stop as 809
Dec 22 18:03:17 axis-b8a44f278c56 systemd[1]: temperature-controller.service: Enqueued job temperature-controller.service/stop as 809
Dec 22 18:03:17 axis-b8a44f278c56 systemd[1]: temperature-controller.service: Job 809 temperature-controller.service/stop finished, result=done
Dec 22 18:03:18 axis-b8a44f278c56 systemd[1]: temperature-controller.service: Trying to enqueue job temperature-controller.service/start/replace


Best Regards,

Christopher Wong

________________________________
From: Andrei Borzenkov <arvidjaar at gmail.com<mailto:arvidjaar at gmail.com>>
Sent: Tuesday, December 21, 2021 8:24:35 AM
To: Christopher Wong; systemd-devel at lists.freedesktop.org<mailto:systemd-devel at lists.freedesktop.org>
Subject: Re: [systemd-devel] After= and Wants= doesn't seem to have an effect

On 20.12.2021 17:05, Christopher Wong wrote:
>> # /etc/systemd/system/iris-detection.service
>> [Unit]
>> Description=Iris detection
>> PartOf=opticsd.service
>
>
> How can you tell that it is a loop? iris-detection.service doesn't have any After= as you stated below.

Yes, sorry, you are right.

> Is it due to the PartOf=opticsd.service?
>

I do not think so. Still, loop is possible due to some other dependencies, it is also
possible that actual unit definitions are different (e.g. units files have been changed
after systemd read them).

Running with debig log level may give some more hints.

>
> Best Regards,
>
> Christopher Wong
>
> ________________________________
> From: systemd-devel <systemd-devel-bounces at lists.freedesktop.org<mailto:systemd-devel-bounces at lists.freedesktop.org>> on behalf of Andrei Borzenkov <arvidjaar at gmail.com<mailto:arvidjaar at gmail.com>>
> Sent: Monday, December 20, 2021 1:27:42 PM
> To: systemd-devel at lists.freedesktop.org<mailto:systemd-devel at lists.freedesktop.org>
> Subject: Re: [systemd-devel] After= and Wants= doesn't seem to have an effect
>
> On 20.12.2021 15:06, Christopher Wong wrote:
>> # /etc/systemd/system/iris-detection.service
>> After=temperature-controller.service
>>
>> # /usr/lib/systemd/system/temperature-controller.service
>> After=iris-detection.service
>
> This is loop and systemd is free to break it by ignoring some dependency.
>

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