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Re: updating list of substitutes


From: Pjotr Prins
Subject: Re: updating list of substitutes
Date: Tue, 26 May 2015 14:42:54 +0200
User-agent: Mutt/1.5.21 (2010-09-15)

I am getting really tired of looking at

  substitute-binary: updating list of substitutes from 'http://hydra.gnu.org'...

> What I have learned is that:
> 
> 1. We now have a tar-ball install (awesome!)
> 2. The DB is the authority
> 3. We can't reconstruct the DB from the store 
> 4. Every release fixates the dependencies so if we know the exact
>    release we can recreate the same dependencies 
> 5. We reload the list of substitutes after a fixed time
> 
> Correct?
> 
> One more below on (5):
> 
> On Tue, Apr 21, 2015 at 10:40:28AM +0200, Pjotr Prins wrote:
> > > > Q1: Do we retain older builds of binaries for some time for download?
> > > 
> > > Yes, but the amount of time is unspecified.
> > > 
> > > On hydra.gnu.org it can be quite long in practice, so that would call in
> > > favor of increasing the default TTL in ???guix substitute???.
> > > 
> > > In the longer run, we need servers to advertise their TTL (someone
> > > running ???guix publish??? may have a different TTL.)
> > > 
> > > > Q2: Can we switch off updating list of substitutes? A command line
> > > >     switch would do. '--no-update-supstitutes'
> > > 
> > > No.
> 
> Let me rephrase. Can we have a more lazy approach towards fetching
> substitutes? Rather than a fixed TTL we could fetch the latest list on
> the first failed substitute. I expect, in practise that would save a
> lot of downloads which turn out to be very slow, even on decent
> internet connections. It also saves load on the build server.
> 
> It does mean the initial binary/build overview on package install can
> be wrong but since we retain binaries for a long time (in practise) it
> would be more likely to change between releases anyway. A simple
> message would do:
> 
>   INFO: failed download of substitute XXX (you may want to pull the latest 
> release)
>   INFO: substitute list downloading...
>   INFO: updated substitute list. The following packages will now be built:
>     1. etc etc.
> 
> I think this is actually safer and fairer than a TTL.
> 
> Pj.
> 
> 

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