Apt layer released

Thu Jan 28 17:15:53 UTC 2016

This is so cool! I hope we can integrate this in the bigdata Charms.
Letting users install additional dependencies is something that would come
in handy!

2016-01-28 16:48 GMT+01:00 Stuart Bishop <stuart.bishop at canonical.com>:

> The Apt layer is more code broken out from my PostgreSQL charm work
> that will be used by future Cassandra charm work.
>
> It provides a simple, charms.reactive friendly interface for dealing
> with apt sources and deb packages. But I think its main utility is
> providing consistent configuration for those extra features required
> for real world production deploys without charmers needing to add a
> single line of code; specifying custom apt sources, package signing
> keys, package version pinning, and a list of arbitrary additional
> packages to install. It also finally documents these options,
> previously only found in the bowels of charmhelpers.core.fetch (which
> provides the underlying implementation).
>
>
>
> # Apt layer
>
> The Apt layer for Juju enables layered charms to more easily deal with
> deb packages and apt sources in a simple and efficient manner. It
> provides consistent configuration for operators, allowing them to
> easily specify custom apt sources and additional debs required for
> their particular installations.
>
> ## Configuration
>
> The charm may provide defaults for these service configuration
> (config.yaml) options, and the operator may override them as required.
>
>     * `extra_packages`
>
>       A space separated list of additional deb packages to install on
>       each unit.
>
>     * `package_status`
>
>       'install' or 'hold'. When set to hold, packages installed using
>       the Apt layer API will be pinned, so that they will not be
>       automatically upgraded when package updates are performed. 'hold'
>       is particularly useful for allowing a service such as Landscape
>       to automatically apply security updates to most of the system,
>       whilst holding back any potentially service affecting updates.
>
>     * `install_sources`
>
>       A list of apt sources containing the packages that need to be
> installed.
>       Each source may be either a line that can be added directly to
>       sources.list(5), or in the form ppa:<user>/<ppa-name> for adding
>       Personal Package Archives, or a distribution component to enable.
>       The list is a yaml list, encoded as a string. The nicest way of
>       declaring this in a yaml file looks like the following (in
> particular,
>       the | character indicates that the value is a multiline string):
>
>       ```
>         install_sources: |
>             - ppa:stub/cassandra
>             - deb http://www.apache.org/dist/cassandra/debian 21x main
>       ```
>
>     * `install_keys`
>
>       A list of GPG signing keys to accept. There needs to be one entry
>       per entry in install_sources. null may be used if no keep is
>       needed, which is the case for PPAs and for the standard Ubuntu
>       archives. Keys should be full ASCII armoured GPG public keys.
>       GPG key ids are also accepted, but in most environments this
>       mechanism is not secure. The install_keys list, like
>       install_sources, must also be a yaml formatted list encoded as
>       a string:
>
>       ```
>         install_keys: |
>             - null
>             - |
>               -----BEGIN PGP PUBLIC KEY BLOCK-----
>               Version: GnuPG v1
>
>
> mQINBFQJvgUBEAC0KcYCTj0hd15p4fiXBsbob0sKgsvN5Lm7N9jzJWlGshJ0peMi
>
> kH8YhDXw5Lh+mPEHksL7t1L8CIr1a+ntns/Opt65ZPO38ENVkOqEVAn9Z5sIoZsb
>
> AUeLlJzSeRLTKhcOugK7UcsQD2FHnMBJz50bxis9X7pjmnc/tWpjAGJfaWdjDIo=
>               =yiQ4
>               -----END PGP PUBLIC KEY BLOCK-----
>       ```
>
> ## Usage
>
> Queue packages for installation, and have handlers waiting for
> these packages to finish being installed:
>
> ```
> from reactive import apt
>
> @hook('install')
> def install():
>     apt.queue_install(['git'])
>
> @when_not('apt.installed.gnupg')
> def install_gnupg():
>     apt.queue_install(['gnupg'])
>
> @when('apt.installed.git')
> @when('apt.installed.gnupg')
> def grabit():
>     clone_repo()
>     validate_repo()
> ```
>
> ### API
>
> Several methods are exposed in the reactive.apt Python package.
>
>     * `add_source(source, key=None)`
>
>       Add an apt source.
>
>       A source may be either a line that can be added directly to
>       sources.list(5), or in the form ppa:<user>/<ppa-name> for adding
>       Personal Package Archives, or a distribution component to enable.
>
>       The package signing key should be an ASCII armoured GPG key. While
>       GPG key ids are also supported, the retrieval mechanism is insecure.
>       There is no need to specify the package signing key for PPAs or for
>       the main Ubuntu archives.
>
>       It is preferable if charms do not call this directly to hard
>       coded apt sources, but instead have these sources listed
>       as defaults in the install_sources config option. This allows
>       operators to mirror your packages to internal archives and
>       deploy your charm in environments without network access.
>
>       Sets the `apt.needs_update` reactive state.
>
>     * `queue_install(packages, options=None)`
>
>       Queue one or more deb packages for install. The actual package
>       installation will be performed later by a handler in the
>       apt layer. The `apt.installed.{name}` state will be set once
>       the package installed (one state for each package).
>
>       If a package has already been installed it will not be reinstalled.
>
>       If a package has already been queued it will not be requeued, and
>       the install options will not be changed.
>
>     * `installed()`
>
>       Returns the set of deb packages installed by this layer.
>
>     * `purge(packages)`
>
>       Purge one or more deb packages from the system
>
> --
> Stuart Bishop <stuart.bishop at canonical.com>
>
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