Re: s6-rc: timeout questions

["Laurent Bercot" <ska-supervision@skarnet.org>]

>- Am I correct in thinking that if a service has properly configured
>timeout-kill and timeout-finish, timeout-down becomes unnecessary and
>even undesirable as it can leave services in an undefined state limbo?
>I know the documentation pretty much says so, but I'm still a bit
>confused by the existence of timeout-down to begin with, if it's
>redundant and unhelpful.

  timeout-kill and timeout-finish are a s6 thing: if present, they're
just copied as is to the service directory that will be managed by
the s6 supervision tree.
  timeout-up and timeout-down are specific to s6-rc: they will be
embedded into the compile database. They do not interact with s6 at
all, they're just a rule for the s6-rc state machine: if the
service does not report being up (resp. down) by the timeout, then
s6-rc marks the transition as failed and stops looking at what
happens with the service.

  For longruns, yes, timeout-kill ensures that the service will
eventually be brought down no matter what. But there are cases where
you *do not want* to kill -9 a daemon (and need a timeout-kill of 0).
timeout-down is useful here, even if it's a pretty niche case.

  And then, of course, the point is that it's needed for oneshots,
which do not have the s6 mechanisms.


>- Can you confirm that timeout-up and timeout-down are also used with
>oneshots? They are defined in the s6-rc-compile documentation, but the
>s6-rc documentation doesn't specifically mention them for oneshots
>state transitions.

  Yes, I confirm that they're also (and primarily) used with oneshots.
They're defined in the "atomic services" section, which comprises
longruns *and* oneshots.

--
  Laurent