On Tue, Jun 23, 2020 at 08:30:37AM -0400, Josh Boyer wrote:
On Tue, Jun 23, 2020 at 8:01 AM Miro Hrončok
> On 22. 06. 20 21:36, Josh Boyer wrote:
> >> I'd like to ask whether RHEL 9 has decided for default modular streams
> >> their failure in Fedora, whether this decision is final and what was the
> >> reasoning behind it.
> > That's an interesting question. I think for the purposes of this
> > discussion, we should acknowledge that usage of default module streams
> > in Fedora and usage in RHEL aren't equivalent. Therefore, failure of
> > adoption in Fedora doesn't necessarily equate to failure in RHEL.
> > With that context, I'll continue.
> Before we continue with that context, could you please elaborate on this?
If I must.
> Obviously we can say "usage of default module streams in Fedora and RHEL is
> different" and to some extent this will always be true. However I would like
> know why they are *significantly* different to justify saying the failure in
> Fedora does not necessarily mean RHEL would experience the same failure.
For all the same reasons SCLs and containers are widely used and
adopted in RHEL, but not Fedora. (And before people say "Fedora has
containers", I know that. They're fine. That doesn't mean you see a
massive adoption of Fedora base images on a wide scale.)
> What makes RHEL so different that the failure is not relevant to it? Is it the
> stable nature of RHEL content? Is it the limited scope of RHEL content? Is it
> the less "wild" development process? Is it something different?
- Moves much much slower
- Has a base distribution that is extremely stable and does not
version bump often across the "platform" layer of libraries, etc
- Has a lifecycle that is equivalent to 20 Fedora releases (yes, twenty)
- Has a broader downstream ecosystem of ISVs and products that require
stability and continuity
A default module stream in Fedora, which is only around for 13 months,
provides little value when the next Fedora release likely is going to
have a different default or a newer version in 6mo anyway. Fedora
moves the entire distribution too fast for there to be a lot of usage
there. RHEL can pin on a default and have that be the default on a
long enough timeline that it actually works.
I have most definitely been less involved than Miro on the modularity work, so I
may be wrong (and will happily stand corrected if so) about the following.
If I understood correctly one of the major issue with default streams were
basically upgrades: how do we go from Fn to Fn+1?
RHEL has the advantages that your points #1 and #3 above high-light, however, I
expect that the upgrade question of default stream will still show up between
say RHEL8 and RHEL9.
I seem to recall that RHEL does not officially support upgrades from version N
to N+1, is that correct?
If so, there is right here a key difference between Fedora and RHEL: the life
cycle of a default stream is fixed to the life cycle of the underlying OS
without supported possibilities to move from version N to N+1.
If we were to do that in Fedora (not support N -> N+1), it is likely that the
default stream question would be much less problematic and vice-versa if Red Hat
start supporting upgrades from RHEL8 to RHEL9, the default stream question would
likely become much more challenging there.