Re: Services and log management/monitoring

["Ludovic Courtès" <ludo@gnu.org>]

Hi,

rendaw <7e9wc56emjakcm@s.rendaw.me> skribis:

> I think fundamentally what I'd most like to know is when should I use a
> Shepherd service vs a non-Shepherd service.  Maybe it's as simple as: if
> you don't have any specific requirements always define a Shepherd service.

It’s hard to answer that question in the abstract.  Do you have an
example in mind that we could work through?

> As a metaphor, maybe Shepherd services would be similar to the plain
> units in systemd.

Yes, I think so.

> Beyond what a service actually is though I have a few more questions:
>
> * Both
> https://www.gnu.org/software/guix/manual/en/html_node/Service-Composition.html
> and
> https://www.gnu.org/software/guix/manual/en/html_node/Shepherd-Services.html#Shepherd-Services
> appear to show a dependency graph.

The first page shows a service extension graph.

The second page shows a graph of dependencies among Shepherd services.

These are two different beasts.

>   Are the dependency graphs Shepherd and non-Shepherd services
> entirely separate?  Or maybe I'm completely misunderstanding
> "extension" in this context.  Can an inet service depend on a non-inet
> service?  Can an inet service depend on a d-bus service?  * Is there a
> way to hook into service events - that is, run some code when a
> service starts or stops?

An inetd service cannot “depend” on a non-inetd service; a D-Bus service
cannot depend on a non-D-Bus service.  Both D-Bus and inetd have their
own notion of what a service is, how to start it, etc., which is
separate from what the Shepherd does.

I reckon that calling everything a “service” does not help understand
all this…

HTH,
Ludo’.