Working with actions

Actions are scripts that are triggered via the client, and applied to a unit. They are described within individual charms. An action’s parameters are defined as a map in a YAML file, and are validated against the schema defined in actions.yaml. See Actions for the charm author for detailed information.

Action commands

The following commands are used to manage actions:

  • actions : list actions defined for a service
  • run-action : queue an action for execution
  • show-action-output : show output of an action by ID
  • show-action-status : show status of all actions filtered by optional ID

Command 'actions'

Lists the actions defined for an application.

For example, with the ‘git’ charm deployed, you can see the actions it supports:

juju actions git

Sample output:

Action            Description
add-repo          Create a git repository.
add-repo-user     Give a user permissions to access a repository.
add-user          Create a new user.
get-repo          Return the repository's path.
list-repo-users   List all users who have access to a repository.
list-repos        List existing git repositories.
list-user-repos   List all the repositories a user has access to.
list-users        List all users.
remove-repo       Remove a git repository.
remove-repo-user  Revoke a user's permissions to access a repository.
remove-user       Remove a user.

To show the full schema for all the actions on an application, append the --schema option.

For example:

juju actions git --schema --format yaml

Partial output:

add-repo:
  additionalProperties: false
  description: Create a git repository.
  properties:
    repo:
      description: Name of the git repository.
      type: string
  required:
  - repo
  title: add-repo
  type: object

The full schema is under the properties key of the root action. Actions rely on JSON-Schema for validation. The top-level keys shown for the action (description and properties) may include future additions to the feature.

Command 'run-action'

Triggers an action.

This command takes a unit (or multiple units) as an argument and returns an ID for the action. The ID can be used with juju show-action-output <ID> or juju show-action-status <ID>.

If an action requires parameters, these can be passed directly. For example, we could create a new ‘git’ repository by triggering the ‘add-repo’ action and following this with the name we’d like to give the new repository:

juju run-action git/0 add-repo repo=myproject

This will return the ID for the new action:

Action queued with id: 3a7cc626-4c4c-4f00-820f-f881b79586d10

As mentioned, this command can be applied to more than one unit (of the same application). So if there were two git units you can also do:

juju run-action git/0 git/1 add-repo repo=myproject

To run an action on an application leader append the string “/leader” to the application name:

juju run-action postgresql/leader switchover --string-args master=postgresql/1

When running short-lived actions from the command line, it is more convenient to use the --wait option. This causes the client to wait for the action to run, and then return the results and other information in YAML format.

For example:

juju run-action git/0 list-repos --wait

Sample output:

action-id: 09563275-87bc-4224-81ef-8282ad7e9d63
results:
  docs1: /var/git/docs1.git
  myproject: /var/git/myproject.git
status: completed
timing:
  completed: 2017-06-18 11:20:10 +0000 UTC
  enqueued: 2017-06-18 11:20:07 +0000 UTC
  started: 2017-06-18 11:20:10 +0000 UTC

This avoids having to run a separate command to see the results of the action (although you can still run show-action-output using the action-id that was returned).

For actions which may take longer to return, it is possible to specify a ‘timeout’ value, expressed in hours(h), minutes(m), seconds(s), milliseconds(ms) or nanoseconds(ns). If the action has completed before the specified period is up, it will return the results as before. If the action has not completed, the command will simply return the ID and status, enabling the user to continue issuing commands. For instance:

juju run-action git/0 list-repos --wait=10ns

Ten nanoseconds isn’t much time to get anything done, so in this case the output will be similar to:

action-id: 10fb05d9-d220-4a07-825e-a1258b1a868b
status: pending
timing:
  enqueued: 2017-06-18 11:27:15 +0000 UTC

You can also set parameters indirectly via a YAML file, although you can override those parameters by providing them directly. Consider the contents of a file params.yaml:

repo: myproject
sure: no

We could then remove the ‘myproject’ git repository in this way:

juju run-action git/0 remove-repo --wait --params=params.yaml sure=yes

If you have an action that requires multiple lines, use YAML quoting. In the below example, ‘foo’ is an action and ‘bar’ is a parameter defined in file actions.yaml (shown right after):

juju run-action unit/0 foo bar="'firstline
secondline
thirdline
fourthline'"

YAML quoting uses both single ’ and double " quotes to surround the part that should not be moved to one line.

The contents of actions.yaml:

#!/usr/bin/python3

from subprocess import call
import sys
with open("/tmp/out", mode='w') as out:
  call(['action-get','bar'],stdout=out)
sys.exit(0)

Command 'show-action-output'

Shows the results returned from an action with the given ID.

To see the output from the add-repo action we executed earlier, we’d enter the following:

juju show-action-output 3a7cc626-4c4c-4f00-820f-f881b79586d10

Sample output:

results:
  dir: /var/git/myproject.git
status: completed
timing:
  completed: 2018-06-18 13:46:12 +0000 UTC
  enqueued: 2018-06-18 13:46:11 +0000 UTC
  started: 2018-06-18 13:46:11 +0000 UTC

Command 'show-action-status'

Queries the status of an action.

We could check on the progress of git’s add-repo action in this way:

juju show-action-status 3a7cc626-4c4c-4f00-820f-f881b79586d1

This will output the status of the action, shown here as ‘completed’:

actions:
- id: 3a7cc626-4c4c-4f00-820f-f881b79586d1
  status: completed
  unit: git/0

There are five possible values for the status of an action:

  • pending : the default status when an action is first queued.
  • running : the action is currently running.
  • completed : the action ran to completion as intended.
  • failed : the action did not complete successfully.
  • cancelled : the action was cancelled before being run.

Debugging actions

To debug actions, use the debug-hooks command, like this:

juju debug-hooks <unit> [action-name action-name2 ...]

For example, if you want to check the add-repo action of the ‘git’ charm, use:

juju debug-hooks git/0 add-repo

Learn more about debugging charms on the Debugging hooks page.

Last updated 3 months ago. Help improve this document in the forum.