bug#28765: [PATCH] config: Conditionally configure daemon offload script.

[Eric Bavier <ericbavier@centurylink.net>]

On Tue, 10 Oct 2017 16:17:46 +0200
ludo@gnu.org (Ludovic Courtès) wrote:

> Eric Bavier <ericbavier@centurylink.net> skribis:
> 
> > On Tue, 10 Oct 2017 08:49:49 +0200
> > ludo@gnu.org (Ludovic Courtès) wrote:
> >  
> >> Hello,
> >> 
> >> Eric Bavier <ericbavier@centurylink.net> skribis:
> >>   
> >> > On Mon, 09 Oct 2017 23:07:10 +0200
> >> > ludo@gnu.org (Ludovic Courtès) wrote:
> >> >    
> >> >> Eric Bavier <bavier@cray.com> skribis:
> >> >>     
> >> >> > From 984e324370c2c17d8d1a982adf2884112c9e64b7 Mon Sep 17 00:00:00 2001
> >> >> > From: Eric Bavier <bavier@cray.com>
> >> >> > Date: Mon, 9 Oct 2017 13:58:04 -0500
> >> >> > Subject: [PATCH] config: Conditionally configure daemon offload script.      
> >> >>                    ^
> >> >> Nitpick: rather “build:”, which is for all things build-related.
> >> >>     
> >> >> > * config-daemon.ac (nix/scripts/offload): Configure only if offloading enabled.      
> >> >> 
> >> >> It LGTM, but is it helpful?  guix-daemon does not invoke ‘guix offload’
> >> >> when it’s missing, as can be seen in guix-daemon.cc:
> >> >> 
> >> >>   #ifdef HAVE_DAEMON_OFFLOAD_HOOK
> >> >>         /* Use our build hook for distributed builds by default.  */
> >> >>   …    
> >> >
> >> > Or maybe something like this would be preferable, to avoid exporting
> >> > NIX_BUILD_HOOK if Guix has been configured to disable the daemon
> >> > offload hook?
> >> >
> >> > --- a/build-aux/pre-inst-env.in
> >> > +++ b/build-aux/pre-inst-env.in
> >> > @@ -50,13 +50,9 @@ NIX_LIBEXEC_DIR="@abs_top_builddir@/nix/scripts" # for 'guix-authenticate'
> >> >  export NIX_ROOT_FINDER NIX_SUBSTITUTERS NIX_LIBEXEC_DIR
> >> >  
> >> >  NIX_BUILD_HOOK="$abs_top_builddir/nix/scripts/offload"
> >> > -if [ -x "$NIX_BUILD_HOOK" ]
> >> > -then
> >> > -    export NIX_BUILD_HOOK
> >> > -else
> >> > -    # No offloading support.
> >> > -    unset NIX_BUILD_HOOK
> >> > -fi
> >> > +@BUILD_DAEMON_OFFLOAD_TRUE@export NIX_BUILD_HOOK
> >> > +@BUILD_DAEMON_OFFLOAD_FALSE@# No offloading support.
> >> > +@BUILD_DAEMON_OFFLOAD_FALSE@unset NIX_BUILD_HOOK    
> >> 
> >> It’s nicer (you’re welcome to push this change!), but it’s equivalent to
> >> what’s already here, no?  
> >
> > It's not quite equivalent.  The current situation would end up always
> > exporting NIX_BUILD_HOOK because it is always generated by
> > config.status.  
> 
> Oooh, got it.
> 
> >> Is there a problem that we are trying to solve in the first place, or is
> >> it more about making things nicer?  
> >
> > The problem is libstore/build.cc executing NIX_BUILD_HOOK even if the
> > daemon offload hook is disabled, i.e. when guile-ssh is missing.
> >
> > Make sense?  
> 
> Yes, definitely.
> 
> Then you can definitely commit the pre-inst-env.in patch; the
> config-daemon.ac patch can’t hurt either.

pre-inst-env patch pushed as 7740228e3523e3e0e4c007eb1f1b224575d16574