On 05/28/2015 05:35 PM, Simo Sorce wrote:
On Thu, 2015-05-28 at 17:18 +0200, Ludwig Krispenz wrote:
On 05/28/2015 05:03 PM, Martin Kosek wrote:
On 05/28/2015 04:59 PM, Ludwig Krispenz wrote:
On 05/28/2015 04:46 PM, Simo Sorce wrote:
On Thu, 2015-05-28 at 15:54 +0200, Ludwig Krispenz wrote:
On 05/28/2015 03:26 PM, Simo Sorce wrote:
On Thu, 2015-05-28 at 14:11 +0200, Petr Spacek wrote:
On 28.5.2015 10:49, Martin Kosek wrote:
On 05/28/2015 09:05 AM, Petr Spacek wrote:
On 28.5.2015 08:55, Jan Cholasta wrote:
Dne 26.5.2015 v 16:32 Petr Spacek napsal(a):
On 26.5.2015 16:16, Martin Kosek wrote:
On 05/26/2015 04:13 PM, thierry bordaz wrote:
On 05/26/2015 02:12 PM, Petr Spacek wrote:
Hello,

it came to my mind that domain level for topology plugin should
actually be
number 2, not 1.

We already used number 1 for incompatible changes in DNS tree and I
believe
that it is not a good idea to have two places which say 'version 1'
but and
actually mean two different things. (DNS tree version 1 + domain
level 1)

Patch is attached.



Hello,
The fix looks good but that seems strange to have to set the initial
version of
the topology plugin to 2.0. (IIUC That is the version that will be
written in
dse.ldif)
I would rather expects that topology plugin 1.0, would activate
itself if the
DomainLevel is 2.0 or more.
If topology plugin 1.0 sets an internal DomainLevel_trigger=2.0 then
activate
itself if DomainLevel >= DomainLevel_trigger.

Let's wait for Ludwig feedback.

thanks
thierry
My personal opinion on this is to start with Domain Level 1
regardless. We
already "solved" the DNS forwarders otherwise, with docs, async
updates etc. I
do not think we will be returning to implementing proper Domain Level
support
for that anyway.

So I rather think that all the "Domain Level starts with 0, 1 is
unused, 2 is
the top one" will cause unforeseen issues I would rather like to avoid.
I'm more worried about confusion in future. To to me it simply seems
easier to
bump one integer now than to document and explain (to users & new
developers)
why we have two "ones" which mean something else.

Code-wise it is just an integer.

Also, it can simplify logic in future when we decide to do another
incompatible change in DNS tree because we will have only one integer
to test
(instead of checking two separate version attribute in DNS tree & domain
level).
+1, but I think the minimum supported domain level should be 1, not 0,
because
0 means the server uses the old DNS schema, which we do not support
anymore,
right?
Good point!

It may be a good point, but it does not make the situation easier. You still
have RHEL/CentOS 6.x IPA out there, where some of them already support
the new
DNS forwarders and some don't - and neither of them support Domain Levels -
i.e. have Domain Level 0.

As I said, I still see more complications with this proposals than
benefits...
I would argue that it actually helps.

If domain level = 1 then we can be *sure* that all replicas support the new
DNS semantics.

If domain level = 0 then we know nothing (because of patched RHEL 6) and
it is
a warning sign for diagnostic tools and also us when it comes to debugging.
First of all  a domain level is something we change *RARELY*, and it is
a whole number and it is an all or nothing thing.

I do not understand why plugin versions matter at all, plugin version
have nothing to do with domain levels. Each plugin *whatever* the
version MUST always support at least 2 levels, because every domain you
have will have to go through a domain_level transition when a new domain
level comes out.

Finally no single developer should be allowed to decide on  anew domain
level, this must be a well ponder team decision as all plugins that need
to change behavior based on domain level will be affected so a thorough
review of what changes are needed across all plugins must be done every
time someone propose a change that requires a domain level bump.

Last but not least we should consider domain levels as something that
changes *very* slowly, because otherwise you'll have to support many
domain levels within any plugins that have to change behavior according
to the domain level.
I would say that the domain level should not change more frequently than
once a year or so. It would be too much code churn to do otherwise.

So for now domain_level should be set to 0. And the topology plugin will
be enabled only when we turn it to 1. However we shouldn't turn it to 1
until we have the replica promotion code at least, because only then we
can make full use of the topology plugins.

The DNS mess is unfixable, unless Petr you volunteer to backport code to
change the behavior of the DNS based on the domain level, if that's the
case then you can tie old behavior to level 0 and new behavior to level
= 1, but I do not think you want to do that given we already have
"level 0" servers that sport the new code and changed the data in the
directory, so let's just ignore DNS for the purpose of this discussion,
except for nothing that once we finally switch to level 1 then all
servers must be running with the newer DNS schema and older is not
supported.

Ah, I almost forgot, there is no "domain level for XYZ plugin", the
domain level is one for the whole server, I want to make it very clear,
because the title and part of the discussion seem to imply that you have
per-plugin domain levels. If anything like that actually exist in the
topology plugin code it must be ripped out now, plugin version and
domain level are completely disjointed things and no correlation should
or can exist, the only thing that can exist is whether the server, as a
whole, supports a specific domain level or not.

So once we decide domain level X comes to existence we basically freeze
what it means and any new development that may require a domain level
bump risk being delayed until we are ready for a new domain level bump,
which should not happen very often.

So let's make it very clear what level 1 means because the next release
will then support only 0 and 1, and once a new version will come out
with support for "level 2" we want be able to use any of the features
tied to level 2 until all servers in the next release have been
upgraded, and that may be a years long process, so we can't just churn
domain level numbers as we need to support working on older levels for
extended periods.
Hi Simo,

you say the topology plugin should only activate itself if the domain
level is >= 1, at the moment this is done
by checking if plugin_version (1.0) >= domain_level (1).
I do not understand what this means

If you want a different method/fields for decision, how do you want it
handled ?
I do not see why you need to check for the topology plugin version, what
you need is a "min_domain_level" version for now and just check:
if domain_level >= min_domain_level:
      do stuff
but right now installation sets
ipaMinDomainLevel: 0
ipaMaxDomainLevel: 1

in the master entry, so we would always do stuff.
Topology should not care about these settings at all, this is only for
domainlevel API to validate if the level can be raised or not. Topology plugin
should be only checking the effective Domain Level in cn=ipa,cn=etc,SUFFIX.
and then ? it reads domain level to be say 1, what is the trigger.
now I am confused, Simo say it should not compare it to the plugin
version, you say it should not compare to the server level,

so what ? hard code on domain level 1?
In the plugin you should have this variable as a global (for the plugin)

int topology_min_domain_level = 1

You *know* the plugin can activate only if domain_level is 1, it is ok
to hard code it, once we release the code we will never change this.
The plugin will be forever and ever enabled only if the global domain
level you read from cn=ipa,cn=etc,SUFFIX is >= 1
this is ok, if we all agree
only this thread started suggesting that the plugin should only start when it is >= 2 and have level 1 for the DNS stuff - so, even if this wasn't valid, sometimes it could help to have a config value to compare to.

but I am fine with hard coding it in the plugin to 1

It doesn't matter if in 2025 we are at topology plugin version 7.0 and
the domain level supported are now 0 through 42, you will still enable
the basic behavior at domain level >= 1

Later on additional features may be conditional on other domain levels,
and eventually we may even become incompatible with domain level 1 and
require a higher level, but that will always be something you know
statically in the code, you will never have a reason or a way to
dynamically change domain level support within the plugin.

Simo.


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