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On Wed, Mar 25, 2015 at 3:58 PM, Sean Dague <sean at dague.net> wrote:

> On 03/25/2015 03:16 AM, Deepak Shetty wrote:
> >
> >
> > On Wed, Mar 25, 2015 at 11:29 AM, Deepak Shetty <dpkshetty at gmail.com
> > <mailto:dpkshetty at gmail.com>> wrote:
> >
> >
> >
> >     On Wed, Mar 25, 2015 at 12:58 AM, Ian Wienand <iwienand at redhat.com
> >     <mailto:iwienand at redhat.com>> wrote:
> >
> >         On 03/24/2015 03:17 PM, Deepak Shetty wrote:
> >         > For eg: Look at [1]
> >         > [1]
> https://github.com/stackforge/devstack-plugin-glusterfs/blob/master/devstack/settings
> >
> >         > I would like ability to change these while I use the
> enable_plugin
> >         > apporach to setup devstack w/ GlusterFS per my local glusterfs
> setup
> >
> >         So I think the plugin should do
> >
> >
>  CINDER_ENABLED_BACKENDS=${CINDER_ENABLED_BACKENDS:-glusterfs:glusterfs,lvm:lvm1}
> >
> >         i.e. provide a default only if the variable is unset.
> >
> >
> >     Bah! That was easy, i should have figured that myself :)
> >     Thanks for catching that
> >
> >
> >
> >         This seems like one of those "traps for new players" and is one
> >         concern I have with devstack plugins -- that authors keep having
> to
> >         find out lessons learned independently.  I have added a note on
> this
> >         to the documentation in [1].
> >
> >         -i
> >
> >         [1] https://review.openstack.org/#/c/167375/
> >
> >
> >     Great, i +1'ed it.
> >
> >     Also i posted patch to fix settings file @
> >     https://review.openstack.org/167494
> >
> >
> > Ian,
> >    Looks like usign bash default in settings file of plugin is not
> > working, in my patch it didn't use glusterfs driver, it used LVM
> (default)
> > I think whats happening here is that by the time settings file is
> > sourced, CINDER_ENABLED_BACKENDS is already set to lvm by lib/cinder
> > so settings file's default value is never taken
> >
> > IIUC there are 3 scenarios (taking CINDER_ENABLED_BACKENDS as example
> var) :
> >
> > 1) localrc doesn't have CINDER_ENABLED_BACKENDS and enable_plugin
> >     - Here we want the lib/cinder's default value to be taken
> >     - this should work fine
> >
> > 2) localrc doesn't have CINDER_ENABLED_BACKENDS but has enable_plugin
> > glusterfs
> >     - Here we want the plugin's default values to be taken, but its not
> > as lib/cinder already initialized CINDER_ENABLED_BACKENDS to use lvm
> backend
> >     - Thus broken
> >
> > 3) localrc has both CINDER_ENABLED_BACKENDS and enable_plugin glusterfs
> > specified
> >     - Here we want CINDER_ENABLED_BACKENDS present in my localrc to be
> > chosen
> >     - This will work as by the time settings file is sourced
> > CINDER_ENABLED_BACKENDS is already initialised to my value in localrc
> >
> > So #2 scenario would need some changes in stack.sh handling of plugin
> code ?
>
> Right, so this code runs late enough that you don't get to change the
> defaults. I think that's ok.
>
> I would instead do the following:
>
> 1) CINDER_ENABLED_BACKENDS+=,glusterfs:glusterfs
>
> or
>
> 2) CINDER_ENABLED_BACKENDS=glusterfs:glusterfs
>
> in the plugin.
>
> Clearly, if you've enabled the plugin, you want glusterfs. I think that
> in most cases you probably only want glusterfs as your backend, so
> option #2 seems sensible.
>


#1 is needed for multi-backend testing
#2 is needed for single-backend testing

#2 is what we currently, we blindly override the var, but that forces the
devstack user to
use the config given in the plugin, I wanted a way to either use plugin
config or override it

I think #1 is better, since it gives the power in localrc to do:

1) CINDER_ENABLED_BACKENDS=
This will ensure lib/cinder doesn't populate it and plugin adds
glusterfs:glusterfs for single backend

2) No mention of CINDER_ENABLED_BACKENDS in localrc
This will make it CINDER_ENABLED_BACKENDS=lvm:lvm-driver1,
glusterfs:glusterfs for multi-backend

Also for vars in settings file that are backend specific (hence not touched
by lib/cinder):

GLUSTERFS_LOOPBACK_DISK_SIZE & CINDER_GLUSTERFS_SHARES

They can remain as :
GLUSTERFS_LOOPBACK_DISK_SIZE=${GLUSTERFS_LOOPBACK_DISK_SIZE:-8G}

CINDER_GLUSTERFS_SHARES=${CINDER_GLUSTERFS_SHARES:-"127.0.0.1:
/vol1;127.0.0.1:/vol2"}

(as mentioned in the patch @
https://review.openstack.org/#/c/167494/1/devstack/settings)

This will give the end user the ability to change loopback size and/or
gluster server IPs
based on the needs of his/her local setup

Agree ?

If yes, then we must mention this in the plugin.rst in a nice way for other
plugin writers to
understand properly :) ?

thanx,
deepak


>
>
>         -Sean
>
> --
> Sean Dague
> http://dague.net
>
>
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