Charms upgrade

The Juju command to use is upgrade-charm. For extra guidance see Upgrading applications in the Juju documentation.

Please read the following before continuing:

Note

A charm upgrade affects all corresponding units; upgrading on a per-unit basis is not currently supported.

Upgrade order

There is no special order in which to upgrade the charms. The order described here is based on the upgrade order for OpenStack upgrades, which, in turn, is the order used by internal testing.

Note

Although it may be possible to upgrade some charms concurrently it is recommended that charm upgrades be performed sequentially (i.e. one at a time). Verify a charm upgrade before moving on to the next.

The general order is:

  1. all principle charms

  2. all subordinate charms

The precise order within the group of principle charms is shown in the below table.

Principle charms

Order

Charm

1

percona-cluster or mysql-innodb-cluster

2

rabbitmq-server

3

ceph-mon

4

keystone

5

aodh

6

barbican

7

ceilometer

8

ceph-fs

9

ceph-radosgw

10

cinder

11

designate

12

designate-bind

13

glance

14

gnocchi

15

heat

16

manila

17

manila-generic

18

neutron-api

19

neutron-gateway

20

placement

21

nova-cloud-controller

22

openstack-dashboard

23

nova-compute

24

ceph-osd

25

swift-proxy

26

swift-storage

Upgrade testing for subordinate charms does not follow a prescribed order. Once all the principle charms have been processed all the subordinate charms can then be upgraded in any order.

Perform the upgrade

Prior to upgrading a charm, say keystone, a (partial) output to juju status may look like:

App       Version  Status   Scale  Charm     Store       Rev  OS      Notes
keystone  15.0.0   active       1  keystone  jujucharms  306  ubuntu

Unit             Workload  Agent  Machine  Public address  Ports      Message
keystone/0*      active    idle   3/lxd/1  10.248.64.69    5000/tcp   Unit is ready

Here, as deduced from the Keystone service version of ‘15.0.0’, the cloud is running Stein. The ‘keystone’ charm however shows a revision number of ‘306’. Upon charm upgrade, the service version will remain unchanged but the charm revision is expected to increase in number.

So to upgrade this ‘keystone’ charm (to the most recent promulgated version in the Charm Store):

juju upgrade-charm keystone

The upgrade progress can be monitored via juju status. Any encountered problem will surface as a message in its output. This sample (partial) output reflects a successful upgrade:

App       Version  Status   Scale  Charm     Store       Rev  OS      Notes
keystone  15.0.0   active       1  keystone  jujucharms  309  ubuntu

Unit             Workload  Agent  Machine  Public address  Ports      Message
keystone/0*      active    idle   3/lxd/1  10.248.64.69    5000/tcp   Unit is ready

This shows that the charm now has a revision number of ‘309’ but Keystone itself remains at ‘15.0.0’.

Caution

Any software changes that may have (exceptionally) been made to a charm currently running on a unit will be overwritten by the target charm during the upgrade.

Upgrade target revisions

By default the upgrade-charm command will upgrade a charm to its latest stable revision (a possible multi-step upgrade). This means that intervening revisions can be conveniently skipped. Use the --revision option to specify a target revision.

The current revision can be discovered via juju status output (see column ‘Rev’). For the ceph-mon charm:

App       Version  Status  Scale  Charm     Store       Rev  OS      Notes
ceph-mon  13.2.8   active      3  ceph-mon  jujucharms   48  ubuntu

The latest available stable revision of a charm can be obtained by querying the Charm Store with the charm snap:

sudo snap install charm --classic
charm pull ceph-mon

Sample output:

cs:ceph-mon-48

Based on the above, the ceph-mon charm does not require an upgrade.

Important

As stated earlier, any kind of upgrade should first be tested in a pre-production environment. OpenStack charm upgrades have been tested for single-step upgrades only (N+1).