Charm delivery¶
Overview¶
Juju charms are delivered via the online Charmhub. This page provides charm delivery information in the context of the OpenStack Charms project.
Channels¶
The notion of channels is central to the delivery of the correct OpenStack charm.
By definition, a channel is comprised of three components: track, risk level, and branch. If a component is not specified at deploy time a default value will be used.
Unlike many charms in the Charmhub, the OpenStack Charms project leverages tracks extensively in order to manage a different array of supported charm versions for each supported combination of OpenStack release and Ubuntu series.
The Charmhub can be queried for a charm’s supported channels. For utmost clarity, this should be done on a per-series basis. For example, to query the channels for the glance charm on the ‘focal’ series:
juju info --series focal glance
Alternatively, the Charmhub web site can be visited: https://charmhub.io/glance
Important
For deployments that are running non-channel (legacy) charms, please see special charm operation All charms - migration to channels.
Tracks¶
A charm’s track corresponds to a given release of its payload. When the associated upstream project uses well-known release names, the track will use that name as its version number. Otherwise, the track’s name will typically be based on a version number or a release date. For example:
Charm |
Example tracks |
|---|---|
nova-compute |
wallaby, xena |
ceph-mon |
octopus, pacific |
rabbitmq-server |
3.8, 3.9 |
ovn-central |
21.03, 21.09 |
latest track¶
Generally speaking, the latest track is a special track whose purpose is to
conveniently point to the latest version of a piece of software.
Warning
The OpenStack Charms project strongly advises against the use of the
latest track due to its implicit nature. In doing so, a future charm
upgrade may result in a charm version that does not support your current
OpenStack release.
Risk levels¶
There are four risk levels that are potentially available for any track:
edge, beta, candidate, and stable. Charms will be promoted
through these levels based on the OpenStack Charms team policy on software
maturity.
Branches¶
There is the possibility for a further subdivision of tracks and risk levels into Charmhub “branches”, which are meant to provide short-lived releases (e.g. quick bug fix).
Channels and tracks for OpenStack charms¶
Important
The information in this section will be updated as new tracks become available.
Note
Charms that support the following OpenStack releases will soon be managed by a single track: Queens, Rocky, Stein, and Train.
The below tables give the tracks that are available for several categories of charms across all series.
Group |
Tracks |
|---|---|
OpenStack service charms |
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Ceph charms |
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OVN charms |
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MySQL charms |
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Trilio charms |
|
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Charm |
Tracks |
|---|---|
hacluster |
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pacemaker-remote |
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rabbitmq-server |
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vault |
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percona-cluster |
|
Provider-specific subordinate charms¶
Some services interact with provider-specific subordinate charms in order to enable a specific SDN, storage plugin, etc. Although these are considered supporting charms, they nonetheless often enable specific functionality for an OpenStack service. They therefore follow the same track-naming schema as do the OpenStack service charms.
This is the list of provider-specific subordinate charms:
cinder-ceph
cinder-lvm
cinder-netapp
cinder-purestorage
neutron-openvswitch
neutron-api-plugin-arista
neutron-api-plugin-ironic
neutron-api-plugin-ovn
keystone-saml-mellon
Installation sources¶
Most charms in the OpenStack Charm project support either the
openstack-origin or source configuration option. This options sets the
software sources of the hosting machine.
In order to ensure that a charm’s channel will lead to the installation of the correct software version, these options will be set automatically according to the associated track. This is particularly important when a track spans multiple series (e.g. Ussuri is supported on both the ‘bionic’ and ‘focal’ series).
