Re: [gentoo-dev] [RFC] Deadlines for next Python implementations

[Patrick McLean]

On Mon, 01 Jun 2020 22:27:19 +0200
Michał Górny <mgorny@g.o> wrote:

> Hi, everyone.
>
> I'd like to be more proactive in avoiding the mess like Python 3.6->3.7
> switch were.  For this reason, I think it would be better to set
> and publish some early deadlines.  Even if we aren't going to strictly
> keep to them, it would help people realize how much time there is left
> to finish the preparations.
>
>
> Python 3.6→3.7 migration
> ========================
> We've already switched the profiles but there are still some unmigrated
> packages.  We will continue either migrating them or last riting if
> migration seems unlikely to happen.  Nevertheless, it is wortwhile to
> set some final deadlines.  My proposal is:
>
>
> 2020-08-01  Python 3.7 migration deadline
>
>    After this date, we lastrite all remaining packages that haven't been
>    ported.  This gives people roughly two months, with a ping one month
>    from now.
>
> 2020-09-15  Python 3.6 target removal
>
>    As usual, the interpreter will be kept a bit longer, then moved to
>    ::python.  This accounts for some extra time if people decide to
>    recover last rited packages last minute.

Given that 2020-08-15 is still well over a year before the upstream EOL,
this might be a little premature. How about we the deprecation dates back
by 4 months? We can still have a similar schedule, just a little later. That
way we are deprecating 3.6 less than a year before the EOL upstream.

We can keep the 2.7 removal as-is.

>
> Python 3.7→3.8 migration
> ========================
> The interpreter is stable but there's still lot of migration work to be
> done.  Good news is that because of the delay with 3.7, many packages
> are getting 3.7+3.8 or even 3.7+3.8+3.9 simultaneously, so there will be
> less work in the future.
>
>
> 2020-07-01  Python 3.8 target stable-unmasking goal
>
>    This is not really a deadline but I'd like to aim for resolving
>    depgraph issues and stabilizing everything needed to unmask python3_7
>    target on stable.  Initial set of stablereqs was filed already,
>    and we'll be unmasking the target as soon as the depgraph is clean.
>
> 2020-09-01  Python 3.8 migration warning
>
>    At this point we tell people it's about time to start actively
>    updating their packages.

Under my suggested timeline, I would say we do this 2020-12-01.

> 2020-12-01  Python 3.8 migration deadline
>
>    We lastrite all the unmigrated packages.

This could be pushed back to 2020-05-01 to not be too close to the 3.6
removal. I personally do not have any strong feelings either way about
3.7, so I would be fine removing 3.6 and 3.7 at the same time if that
is easier.

> 2021-01-15  Python 3.7 target removal
>
>    As above.
>
>
> Python 2.7 removal
> ==================
> I would like to continue removing py2.7 from packages where possible,
> and slowly lastriting where clearly impossible.  However,
> for the remaining packages I'd like to set a hard deadline.
>
>
> 2021-01-01  Final Python 2.7 deadline
>
>    That's one year after upstream's EOL.  At this point, we last rite
>    all the remaining py2.7 packages.
>
> 2021-02-15  Python 2.7 target removal
>
>    All packages relying on the target are removed.  The interpreter
>    stays for as long as we need it.
>
>
> General goal
> ============
> As a general goal, I'd like to set timelines like this once we decide
> that the next interpreter goes stable.  The exact lengths are highly
> dependent on properties of the next target.  For example, I suspect
> Python 3.9 will be easier for us; so far my testing has shown issues
> that are rather easy to solve.
>

Here is an attempt at updating version of ASCII art, from what
I can tell, the 'w' at the 3.7->3.8 warning probably belonged
in the 3.7 column, I moved it. As I said above, I am personally
fine if we make 3.6 and 3.7 removals close together (even at
the same time).

Combined timeline
=================
From the above dates:

            2.7 3.6 3.7 3.8
2020-07-01   |   |   |   u    py3.8 target unmasked
             |   |   |   |
             |   |   |   |
             |   |   |   |
             |   |   |   |
             |   |   |   |
             |   |   |   |
2020-12-01   |   |   w   |    py3.7→3.8 migr. warning
             |   |   |   |
             |   |   |   |
2021-01-01   m   |   |   |    py2.7 pkg last rites
             |   |   |   |
             |   |   |   |
2021-02-01   |   m   |   |    py3.6 pkg last rites
             |   |   |   |
2021-02-15   x   |   |   |    py2.7 pkg removal
2021-03-15       x   |   |    py3.6 pkg removal
                     |   |
                     |   |
                     |   |
2021-05-01           m   |    py3.7 pkg last rites
                     |   |
                     |   |
2021-06-15           x   |    py3.7 pkg removal
                         |
                         v