[systemd-devel] `Found ordering cycle on _SERVICE_` loops due to `local-fs.target` with `Requires` instead of `Wants` for mounts generated from `/etc/fstab`

[John Florian]

On 2018-04-25 04:53, Lennart Poettering wrote:
> There have been requests in improving the cycle breaking algorithm,
> but not much has been done in this area, since it's not clear what can
> be done. Ultimately it's just polishing a broken situation, and
> the better way out is to fix things properly, i.e. just correct the
> cycle in the dependencies in the first place.

Having been the author of numerous custom services that are intended to 
wedge into those provided by systemd/Fedora I've faced resolving these 
several times and I've never felt all that competent at the task.  
Lennart, you were immensely helpful on one occasion by pointing me to 
`systemctl show FOO` but even then hunting the problem down was far from 
simple (for me).  I've done the dot/graphviz thing and found it just as 
useless to me as when I've tried applying it to Puppet's 
ordering/dependency looping.  I'm not blaming those tools (or systemd) 
because I'm well aware much of the problem is my inability to use them 
effectively.  The graphs always seem to be overly simple and revealing 
no problem or overly detailed and obscuring the problem.  Compound that 
with "an arrow pointing this way means what exactly?"

Is there anything else that could be done to make hunting these loops 
down easier?  Is there an example of any product that has a similar 
situation where they excel at helping the developer?  Or are we already 
there and I just need more practice?  I'm sure part of my struggle is 
just not encountering these very regularly and integrating into much 
that I'm only partly familiar with, but the result is the same, 
trepidation and loathing.