On 2015-10-02 19:52, Walter Heck wrote:
I'm personally more of a fan of what some programming languages call
interfaces; a sort of contract if you will that a module implements.
Yes that is good - does not solve the issue of modules having the same
name though - either the module name must change, or modules must be
installed with both author and name and then referenced the same way.
- henrik
So for instance olindata::galera could look for any class that
implements the IMysql interface. That way, I don't really need to worry
if the end-user is using puppetlabs::mysql or example42::mysql, as long
as they implement the IMysql interface I can guarantee it does what I need.
This would have pretty heavy impact on how you write code right now, but
it would be a rather elegant solution imho.
interface IMysql::server identified by
'9ff3d80b-b02d-4994-b4da-e1ff205304ea' {
Service['mysql']
Package['mysql-server']
File['apache2.conf']
}
class puppetlabs::mysql implements
IMysql['9ff3d80b-b02d-4994-b4da-e1ff205304ea'] {
[.. SNIP..]
# file, service, package here like normal
}
class example42::mysql implements
IMysql['9ff3d80b-b02d-4994-b4da-e1ff205304ea'] {
[.. SNIP..]
# file, service, package here like normal
}
class olindata::galera {
package { 'galera':
require => Package['IMysql::server::mysql-server']
}
}
Or something along those lines. Question remains where the
IMysql::server interface then needs to be declared, and how we would
manage the GUID registration of interfaces.
Comments, thoughts?
Walter
On Tuesday, February 10, 2015 at 5:52:37 PM UTC+1, henrik lindberg wrote:
On 2015-10-02 1:23, Trevor Vaughan wrote:
> I was talking with a few folks today about potential resolutions to
> module namespace issues.
>
> == Fundamental Issue ==
>
> puppetlabs_apache -- Installs To --> apache
> example42_apache -- Installs To --> apache
> theforeman_apache -- Installs To --> apache
>
> You get my point...
>
> == Current Solutions ==
>
> Right now, there are two ways to solve this problem if you want
some of
> your nodes to use puppetlabs_apache and others to use
theforeman_apache.
>
> 1) Modify the module and force the namespace:
> - puppetlabs_apache -- Installs To --> puppetlabs_apache
> - theforeman_apache -- Installs To --> theforeman_apache
>
> * Isssue: You can't just use outside code at will. You have to
modify
> *everything* that uses the above code.
>
> 2) You have to create a separate environment for each host group
> (potentially each host) that you want to have use the differing
code.
>
> * Issue: This is a LOT of overhead for a couple of modules
and may
> have other ramifications in terms of performance as you get up in
number.
>
> So, would it be possible to allow multiple versions of a module
to exist
> in the same namespace but only use one during a given run?
>
Basically no, this is not possible without adding some kind of
mechanism
to filter out modules on the modulepath. This will need to be done per
environment anyway. Remember that modules can contribute all sorts of
extensions to puppet (faces, indirections, facts, functions, types, and
with future parser also bindings). For performance reasons (and
bootstrapping, etc.) these are scanned when the environment loads (some
scans are lazy, but may take place before manifests really starts to be
evaluated).
- henrik
> == The First Proposal ==
>
> Inspired by RVM Gemsets, how about allowing modules to declare which
> version of a given module they will use?
>
> /etc/puppet/modules/apache/puppetlabs/{files,modules,manifests}
> /etc/puppet/modules/apache/theforeman/{files,modules,manifests}
> /etc/puppet/modules/apache/<author>/{files,modules,manifests}
>
> Then, use could be dictated by something like: include
apache@puppetlabs.
>
> Unfortunately, this really comes down to the parser being able to
> understand the following:
>
> include apache => See if there are any @'s and use that one
> include apache@puppetlabs => include the Puppetlabs apache
> include apache@puppetlabs && include apache@theforeman => Fail,
conflict
>
> == Alternative ==
>
> One possible alternative is to just use the metadata.json file to
> dictate which module will be used when loading other modules.
>
> Again, if there is a conflict, that is a failure but *only* if
the code
> attempts to use both at the same time.
>
> The benefit here is that it should make things very unambiguous
while
> the drawback (if it really is) is that you *must* put a
metadata.json
> file in every module that you create.
>
> This is just a set of thoughts that I hope get us moving in a
direction
> where this type of thing is possible and I look forward to
hearing what
> people think (good, bad, or ugly)!
>
> Thanks,
>
> Trevor
>
> --
> Trevor Vaughan
> Vice President, Onyx Point, Inc
> (410) 541-6699
> tvau...@onyxpoint.com <javascript:> <mailto:tvau...@onyxpoint.com
<javascript:>>
>
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