Apt layer released

[Adam Stokes]

Cool thanks for the additional info, I'm going to integrate this into my
layers now

On Thu, Jan 28, 2016 at 11:46 AM, Stuart Bishop <stuart.bishop at canonical.com
> wrote:

> On 28 January 2016 at 23:01, Adam Stokes <adam.stokes at canonical.com>
> wrote:
> > Why would someone want to use this instead of what's provided in
> > charmhelpers?
>
> This wraps what is provided in charmhelpers.
>
> To use raw charmhelpers, you need to write the hooks and handlers to
> call its features at the right time and in the right order. You need
> to call fetch.configure_sources, whenever the relevant config items
> change. You need to install the list of extra packages, whenever the
> relevant config item changes. You need to repin held packages, if the
> option is set, whenever new packages are installed. To use the layer,
> you just add an entry to layers.yaml and get it all done for you, and
> it is all done consistently across all charms using the layer. You
> don't have to worry about inconsistencies between your
> reimplementation of the wheel with the next charms reimplementation of
> the wheel causing confusion to users.
>
> It also removes all the boilerplate. You don't need to include all
> that gumph in your config.yaml.
>
> It sets reactive states your handlers can wait on so you don't have to
> set reactive states your handlers can wait on.
>
> By requesting a package install and having handlers wait on the
> install to complete, you get to write highly decoupled code without
> losing efficiency. Several different handlers in different parts of
> the code base and even in different layers can all schedule the
> packages they care about to be installed, and have a single apt-get
> update run, and only if necessary.
>
> Improvements to the layer improve all charms using the layer. When
> Juju charm configuration gets richer data structures, we can write all
> the migration, compatibility and deprecation stuff once and all charms
> get it next time they are built. Fixes in the charmhelpers codebase
> can't fix its callsites or improve the documentation in your
> config.yaml.
>
> So you want to use it to save initial work and future maintenance :)
>
>
>
> --
> Stuart Bishop <stuart.bishop at canonical.com>
>
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