Guix services, logging, and log rotation

Guix services, logging, and log rotation

[Katherine Cox-Buday]

Hey Guix!

I'm slowly working on contributing rsyslog with a Guix service. I have just arrived at trying to allow the user to specify where the Shepherd service sends its log file, and I began thinking about log rotation.

In the manual, SS10.8.3, it says:

> (usually, services that produce log files already take care of that)

I found an excellent example in =hpcguix-web-service-type=. It looks like you can achieve this by extending the =rottlog-service-type=?

#+BEGIN_SRC scheme
  (define hpcguix-web-service-type
    (service-type
     (name 'hpcguix-web)
     (description "Run the hpcguix-web server.")
     (extensions
      (list (service-extension account-service-type
                               (const %hpcguix-web-accounts))
            (service-extension activation-service-type
                               (const %hpcguix-web-activation))
            (service-extension rottlog-service-type
                               (const %hpcguix-web-log-rotations))
            (service-extension shepherd-root-service-type
                               (compose list hpcguix-web-shepherd-service))))))
#+END_SRC

However, I noticed not all services allow users to specify where log files go, or setup log rotation. E.g.:

#+BEGIN_SRC scheme
(define syncthing-service-type
  (service-type (name 'syncthing)
                (extensions (list (service-extension shepherd-root-service-type
                                                     syncthing-shepherd-service)))
                (description
                 "Run @uref{https://github.com/syncthing/syncthing, Syncthing}
decentralized continuous file system synchronization.")))
#+END_SRC

Are these bugs?

Why don't all services allow you to specify where logs go?

I guess if no log location is specified, it just goes in the master shepherd log which is rotated?

Thank you,
--
Katherine

Re: Guix services, logging, and log rotation

[Ludovic Courtès]

Hi,

Katherine Cox-Buday <cox.katherine.e@gmail.com> skribis:

> In the manual, SS10.8.3, it says:
>
>> (usually, services that produce log files already take care of that)
>
> I found an excellent example in =hpcguix-web-service-type=. It looks like you can achieve this by extending the =rottlog-service-type=?

Yes (info "(guix) Log Rotation").

> However, I noticed not all services allow users to specify where log files go, or setup log rotation. E.g.:
>
> #+BEGIN_SRC scheme
> (define syncthing-service-type
>   (service-type (name 'syncthing)
>                 (extensions (list (service-extension shepherd-root-service-type
>                                                      syncthing-shepherd-service)))
>                 (description
>                  "Run @uref{https://github.com/syncthing/syncthing, Syncthing}
> decentralized continuous file system synchronization.")))
> #+END_SRC
>
> Are these bugs?
>
> Why don't all services allow you to specify where logs go?

I think these are omissions rather than bugs.  But really, each daemon
has its own way of dealing with logging: some write to syslog (in which
case we don’t need to add a new log rotation rule), some just write to
stderr (like hpcguix-web, and in this case you need to pass #:log-file
to ‘make-forkexec-constructor’), some write to custom log files that may
or may not be configurable.

I think it’s nice in general for services to provide log rotation
entries, especially when they’re likely to produce verbose logs.

HTH,
Ludo’.