Proposal: drop rails and its reverse-dependencies from Ubuntu 19.04 [Re: Maintaining language-specific module package stacks]

[Matthias Klose]

On 06.04.19 00:14, Steve Langasek wrote:
> Hi Balint,
> 
> On Thu, Apr 04, 2019 at 02:45:23PM +0200, Balint Reczey wrote:
>>> This is short-sighted, and greatly influenced by the voices of language-specific
>>> upstream communities.  As seen at several occasions at PyCon: Ask an upstream
>>> community, which Linux distribution they use (majority of hands go up for
>>> Ubuntu), and then how many of those use the system Python (majority of hands go
>>> down).  Please ask this Python question to an upstream Java, upstream Ruby
>>> community, and I assume that nobody cares and uses the Python as distributed by
>>> Ubuntu.  Ask the Java and Python communities the same question about Ruby, and
>>> these are probably happy with the Ruby found on Ubuntu.  Now remove the Ruby,
>>> Python and Java stacks, and probably nobody will be happy anymore.
> 
>> This is very true and this is the raison d'être for distributions.
> 
>> There is also a benefit of having the long tail packages in each
>> language stack that was not mentioned.
> 
>> How would you test the ruby interpreter without the wast amount of
>> gems in the archive? With build-time or hand-made tests?
> 
>> No. The autopkgtest infrastructure that continuously sweeps through
>> the packages in the archive catches the regressions that could have
>> been easily introduced to the archive, but without reverse
>> dependencies of the ruby interpreter no tests would be triggered and
>> we would ship an interpreter that would break our users' systems in
>> million ways.
> 
> The critical limitation here is that an autopkgtest failure by itself only
> tells you "these two package versions when used together cause the test to
> fail".  It takes effort to answer the subsequent questions:
> 
>  - Is this a valid test, or is it based on wrong assumptions?
>  - Is this a regression in the interpreter, or a deliberate change in the
>    language?
>  - Is the package whose test is failing something that we should fix, or is
>    it dead upstream and we should remove it?

you are missing here:

 - is our test infrastructure reliable?
 - are we running the test with the right assumptions?
 - does our test infrastructure allow to pass autopkg tests in all
   conditions?

But this probably is another thread ...

> These questions take even more effort to answer for ruby than for other
> languages, because the Ubuntu developers doing this investigation don't
> actually speak ruby.
> 
> So no, I don't think the long tail of autopkgtests on ruby modules improves
> the quality of the intepreter, in proportion to the effort spent on
> analyzing the autopkgtest failures.
> 
>> Even if big parts of the language stack's are somewhat outdated they
>> were tested together and provide a stable base for building systems on
>> and we should not just slash those big parts as a policy, only drop
>> the pieces which somehow got into the release pocket, but don't let
>> more important packages in due to failing autopkgtests or broken
>> builds.
> 
> We don't really have a lightweight way of deciding that one package is "more
> important" than another, either.

we have that.  It's called the main/universe split.  This isn't reflected in
autopkg tests at all.

>> Regarding rails I agree with dropping it from Disco, but this is more
>> of a call for help to get it in again in Disco+1 if there is a strong
>> community around it rather than discouraging people from maintaining
>> language stacks in Ubuntu or Debian.
> 
> Agreed!  The intention here is absolutely not to say that rails can't be
> part of Ubuntu, but to say that rails in its present state is not a net
> benefit to our users.

In the meantime somebody apparently did remove the packages with failing autopkg
tests which were already removed in Debian.  That's a good thing, however it has
kind of a smell if this only happens after such escalations.

Now the situation is:

rails (2:4.2.10-0ubuntu4 to 2:5.2.2+dfsg-6ubuntu1)
  Invalidated by dependency
  Depends: rails puma (not considered)

puma (- to 3.12.0-2)
  58 days old
  autopkgtest for puma/3.12.0-2: amd64: Regression ♻ , arm64: Regression ♻ ,
    armhf: Regression ♻ , i386: Regression ♻ , ppc64el: Regression ♻ ,
    s390x: Regression ♻

rails is ready to migrate, there is no puma package in the release pocket. the
failing puma autopkg test in -proposed shouldn't be any concern.

Filed LP: #1824049 for that.

Now we could go on removing puma from -proposed, and then rails should migrate.
How can we do that without removal?

So these removal requests come down to archive-removals not being processed on a
regular basis, and an additional removal or britney fix.  Again, please lets fix
these issues first before relying on removals on a large style.

Matthias