Re: s6 usability (was: runit patches to fix compiler warnings on RHEL 7)

From: Jeff <sysinit_at_yandex.com>
Date: Sat, 30 Nov 2019 15:32:01 +0100

30.11.2019, 11:15, "Laurent Bercot" <ska-supervision_at_skarnet.org>:
> This is very interesting. I thought that having a s6- prefix was a *good*
> thing, because I valued clarity above everything, and especially above
> terseness. I understand the advantages of having commands named "sv" and
> "chpst", but I believed, in my naïveté, that it wasn't a good idea for a
> specialized package to tread on a large namespace; and to me the s6-
> prefix would help users recognize exactly the domain of the command
> they're using, and then they could abstract it away and focus on the
> real command name.

totally agreed, Laurent.

using a dedicated namespace prefix like "s6-" is a very good idea.
this avoids nameclashes (i. e. overwriting on installation) with similar
utilities of other supervision suites and frees Laurent from the task
of coming up with proper AND unique command names. consider
nameclashes of several "init" program for example.

the solution here could be a simple symlink to the original s6 tool without
the prefix if you prefer (maybe even located in an other dir than /bin).

> The number of executables is a choice; I like to have more, smaller,
> executables than less, bigger ones. One function, one tool. It makes
> code easier to write; this is not really for historical reasons, it's a
> design choice. Personally, it's easier for me to remember several
> process state change command names than all the options to chpst.
> whenever I use chpst, I always need to check the doc; when I use
> something like softlimit or setuidgid, I may need to check the doc for
> specific options, but I always remember which command I want and its
> general syntax. So, I suppose it comes down to individual preference
> there.

using a single combined tool is more efficient since it avoids wasteful further
exec chaining steps, though.

> Would a generic "s6" command, that takes alternative syntax and rewrites
> itself into "internal" commands, help? It could emulate runit syntax,
> among other things.
>
> s6 runsv ... -> s6-supervise ...
> s6 sv ... -> s6-svc ...
> s6 chpst ... -> various s6-prefixed process state change commands
>
> My plan is for the future s6-frontend package to include such a
> one-stop-shop command that controls various aspects of an s6
> installation,
> but if this command can help with s6 adoption, I can work on it much
> earlier than the rest of the s6-frontend functionality.
>
> Or, if you have other ideas that could help with easier assimilation of
> the s6 commands, I'm very open to suggestions.

Busy/ToyBox style ?

> Would entirely removing s6's dependency on execline help clear that
> misunderstanding and help with s6 adoption? This could be made possible
> by:
> - duplicating el_semicolon() functionality in s6-ftrig-listen.c
> (it's not elegant, but clearing the dep may be worth it)
> - adding an alternative '?' processor directive to s6-log, that spawns
> the processor using /bin/sh instead of execlineb. (The '!' directive
> would still be there; processor invocations using '!' would just fail
> if execline is not installed.)

sounds not too bad, IMO. though i personally can live without it,
especially since the other suites also provide loggers (without any
execline deps of course), he can use dt encore's "multilog" utility.

> s6-rc, however, absolutely cannot do without execline, since it uses
> autogenerated execline scripts.

could you document the way s6-rc works (i. e. its architecture) somewhere ?
or are users requested to follow your C code to find out how it works
exactly ?

> But s6-rc is a different beast, that
> requires a lot more involvement than s6 anyway, and that isn't needed
> at all if we're just talking about runit-like functionality.

indeed.
Received on Sat Nov 30 2019 - 14:32:01 UTC