[chef] pre-update notifications

[Gregoire Seux < >]

Hello,

I'd like to have pre-update notifications which would be the same as
"notifies" but triggered before resource convergence.

For instance, some packages automatically restart a service during
upgrade and I'd like to downtime the host in supervision _before_
actually starting to upgrade those packages.

Classic notifications would be :

>package "cassandra" do
>  notifies :run, "execute[downtime host]"
>end

but notification is triggered _after_ the upgrade so it is not useful
anymore.

I wondered how to do this and came up with a partial solution switching
to why_run  temporarily to find wether a given resource (package) will
be updated during convergence.
An example is https://gist.github.com/kamaradclimber/6306398
which would execute the resource to downtime only if the package will be
upgrade later.

Does anyone has already encountered such need? and fixed it?

-- 
Grégoire