Working with actions

Juju charms can describe actions that users can take on deployed applications.

Actions are scripts that can be triggered on a unit via the command line. Parameters for an action are passed as a map, either defined in a YAML file or given through the UI, and are validated against the schema defined in actions.yaml. See Actions for the charm author for more information.

The following commands are specified for dealing with actions:

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

Action commands

`actions`

Lists the actions defined for a service.

For example, with the 'git' charm deployed, you can see which actions it supports with the following command:

juju actions git

You should see something similar to this:

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 a service, append the --schema argument to the actions command. For example, here's the beginning of the output from juju actions git --schema --format yaml:

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
...

Note: 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.

`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, like this:

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 add the --wait option to this command. This causes the Juju client to wait for the action to run, and then return the results and other information in YAML format.

For example, running the command:

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

Will return something like:

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 also possible to specify a 'timeout' value, expressed in hours(h), minutes(m), seconds(s), milliseconds(ms) or nanoseconds(ns). In this case, 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.

Example params.yaml:

repo: myproject
sure: no

With the above example params.yaml file, we could remove the myproject git repository with the following command:

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 to make sure the whitespace is not collapsed into one line, like in this example where foo is an action and the parameter bar is defined in the actions.yaml file shown just after the example:

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.

Example 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)

`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, for example, we'd enter the following:

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

This will return something like the following:

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

`show-action-status`

Queries the status of an action.

For example, We could check on the progress of git's add-repo action with the following command:

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 5 different 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 <service/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 in Debugging hooks.