more informative logging for (shepherd) services

[Florian Dold]

Hi Guix,

is there a way to obtain more informative logging from services that are
started directly or indirectly (by GuixSD service) via shepherd?

It seems right now, only what is sent to the syslog is logged.  However,
it would be immensely helpful if

1. the actual commands run by the shepherd for a service
2. the stdout/stderr of the service
3. the exit code of a process when it unexpectedly terminates

would also be available.  Is there there a way to enable this or plans
to implement it?

The make-forkexec-constructor of Shepherd does have a log-file
parameter, so (2) is already kind of possible.  However, some GuixSD
services (for example fcgiwrap) do not allow to pass this option down to
the shepherd service.  Any way around this?

I'm currently struggling to get the fcgiwrap service to run, as the logs
only tell me that it couldn't be started, and that it's getting disabled
after too many retries.

Generally, how do folks debug GuixSD/shepherd services?  I found it
pretty difficult, as it looks like the Guile code that defines a service
is minified and somewhere in the store.  Is there a way to ask shepherd
for the definition of a service?

- Florian