Hi William,

Things are not black and white:
there is a huge difference between a fix with limited impact (like adding some check in configuration tools or in the server) and redesigning something that is used in many different contexts for every request handled by the server ...

In the first case we could easily mitigate the risk by testing and be fairly confident, in the second case the tests are too complex to achieve the same confidence and we should take this kind of risk only if there were a serious benefit to balance it, but in this case, there are other solutions with less risks.

I can understand it could seem too conservervative and frustrating but that is the price when working on mature projects. If you do not do that, the product becomes unstable, and users quickly abandon it.

Regards,
Pierre

On Mon, Oct 19, 2020 at 1:27 AM William Brown <wbrown@suse.de> wrote:

> On 16 Oct 2020, at 17:48, Pierre Rogier <progier@redhat.com> wrote:
>
> Hi William,
> I agree with your architecture points and that is why I said my proposal is a less appealing trade off.
>
> My real concern is your last point:
> we just do not know and IMHO we are unable to predict what (or if) config will cause problems, and I am afraid we will only discover it when people start to complain.
> So I still think that the benefit/risk ratio is bad)
>

I think this wasn't my point. The thing is *any* change will have that "unknown" risk. Our job is to qualify and identify as many of those risks as we can, to remove them as unknowns. Think about the work recently to merge the changelog to the main db, or BDB to LMDB work, even changing from perl to python for installation. These are all significantly larger changes, which would be "much riskier" but all of them have been managed effectively by the team communicating, coordinating, analysing, designing and testing changes.

So I really don't accept this "unknown" risk argument. I have laid out a design that explores the configuration, how it works today and how the values are currently trusted, and a process to manage and understand this change in a way to minimise the risk. There are associated tests, and it passes with address sanitiser, and other test cases for mapping trees, replication and others.

If we just say "unknown risk" at every change we make we'd never progress. We may as well packup and go home, the project is completed.

So I still stand by my design and the PR I have submitted in this case, and if there are concerns about esoteric configurations, then we should identify and understand them too beyond the testing I have already provided.

—
Sincerely,

William Brown

Senior Software Engineer, 389 Directory Server
SUSE Labs, Australia
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