[systemd-devel] Depending on services from a service unit template

[Andrei Borzenkov]

01.07.2016 00:50, Paul Menzel пишет:
> Dear Michael, dear Andrei,
> 
> 
> Thank you for replying.
> 
> 
> Am Montag, den 27.06.2016, 15:37 +0200 schrieb Michael Biebl:
>> 2016-06-27 13:49 GMT+02:00 Andrei Borzenkov <arvidjaar at gmail.com>:
>>> On Mon, Jun 27, 2016 at 9:25 AM, Paul Menzel wrote:
> 
>>>> having a template for a service unit like `example at .service`, and
>>>> starting several services from it, is there a way, to let another
>>>> service unit require all services started from that template?
>>>
>>> I do not think it is possible. In other direction it may work with
>>> some workaround (i.e. make every instance of template be required
>>> by specific services).
>>
>> PartOf= in the template service might be what you are looking for.
> 
> From the manual page systemd.unit:
> 
>>        PartOf=
>>            Configures dependencies similar to Requires=, but limited
>> to stopping and restarting of units. When systemd stops or restarts
>> the units listed here, the action is propagated to this unit. Note
>> that this is a one-way dependency — changes to this unit do not
>> affect the listed units.
> 
> So, it could indeed be what I am looking for. In my use case, it
> doesn’t feel right yet though.
> 
> There are several instances of a Web application started from
> example at .service. In front of it is the proxy HAProxy.
> 
> So in my reading, saying that the Web application instances is a *part
> of* HAProxy, doesn’t totally feel/sound right to me.
> 
> Also, asking for `Requires=` was, that HAProxy seems to check the
> configured backends to run, and refuses to start if they don’t. That’s
> why, all the Web applications are required before the HAProxy start-up.
> 
> If I am not mistaken, `PartOf=` does not solve that problem.
> 
> Do you have another suggestion?
> 

This is exact use case I meant. Put

[Install]
RequiredBy=HAProxy.service

in example at .service template; then "systemctl enable
example at instance.service" will automatically add link to
.../HAProxy.service.requires directory.

Downside is that you need to statically configure all instances but as I
understand HAProxy must know them in advance anyway.

In principle, I do not see why we cannot have WantedBy and RequiredBy as
first class directives under [Unit] to spare all these hoops.

-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 198 bytes
Desc: OpenPGP digital signature
URL: <https://lists.freedesktop.org/archives/systemd-devel/attachments/20160701/7f335a94/attachment.sig>