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Re: The 🐑 Shepherd gets a service collection

From: Csepp
Subject: Re: The 🐑 Shepherd gets a service collection
Date: Fri, 17 Mar 2023 10:52:36 +0100

Adam Faiz <> writes:

> On 3/16/23 22:14, Ludovic Courtès wrote:
>> The main limitation of mcron for such thing is that it’s entirely
>> static: it reads a list of job specs upfront and then goes on to
>> schedule them.  There’s no communication protocol to talk to it and
>> add/remove jobs on the fly, which is what ‘at’ would need.
> Would it be easier to add dynamic job spec support to mcron than adding a new 
> command scheduler?

Adding timers to Shepherd means Shepherd services can depend on timers
and vice-versa.

But maybe Shepherd could still reuse mcron code internally.

>>> Regarding syslogd, I think a better approach is to tell the services to 
>>> send their output to stdout and stderror,
>>> so that logs don't depend on a separate logging service in the first place.
>> Yes, but:
>>    1. Some daemons include syslog support even today, sometimes
>> optional,
>>       sometimes mandatory.
>>    2. Syslog is a bit more structured than just stdout/stderr
>> output:
>>       there are facilities and levels, for instance—see syslog(3);
>>       syslogd provides interesting filtering capabilities.
> Thanks, it looks like syslog is still important for structured logs.
> Are there issues of logs sent to syslog being lost even when the syslogd 
> service is specified as a requirement of services that use it?
> If not, I think it's not necessary to add a syslogd implementation to the 
> shepherd.
>  >> Per-service logging is already implemented in the Shepherd, but
>    could be streamlined to have a default logs directory:
>> Interesting read, thanks!
>> Regarding the default logs directory, there’s /var/log already, or
>> did
>> you mean something else?
> I do mean /var/log, I felt like #:log-file in make-forkexec-constructor could 
> be improved.
> Rather than always having to specify the absolute log file path,
> #:log-file could just be set as #t and would then default to
> /var/log/$canonical-name of the service.

That is problematic on flash storage and read-only storage.
Syslog has the advantage of working very nicely in memory only.
Also the structure is very nice, you get to see every event on the
system in a chronological order.  You don't get that with log files.
Honestly /var/log should be redirectable to syslog.

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