Scenario > State
In the context of Scenario, State refers to a monolithic data structure representing all data that is available to a charm at runtime. Simplifying somewhat, that information can be categorized depending on its source:
- data coming from the juju controller and mediated by hook tools
- data coming from the locally stored unit state (the unit state db)
- data coming from environment variables
- data coming from the workload and mediated by Pebble calls in the case of kubernetes charms
The State encapsulates all these types of data in a unified, immutable data structure.
More in detail, the information contained in State can be summarised as follows: in this table you can find
- the name of the State component
- its type in Python (and a link to the reference doc, where available)
- the source of the data at runtime for that component, i.e. what part of the charm runtime this data is meant to mock
- whether the data is writeable by the charm during hook execution
| State component | type | source | write |
|---|---|---|---|
config |
Dict |
hook tool(s): config-get
|
no |
relations |
List[Relation] |
hook tool(s): relation-[get\|set\|list\|ids]
|
no* |
networks |
List[Network] |
hook tool(s): network-get
|
no |
unit_status |
StatusBase |
hook tool(s): status-[get\|set]
|
yes |
app_status |
StatusBase |
hook tool(s): status-[get\|set]
|
yes |
workload_version |
str |
hook tool(s): workload-version-set
|
yes |
leader |
bool |
hook tool(s): is-leader
|
no |
secrets |
List[Secret] |
hook tool(s): secret-[get\|set\|grant\|revoke\|add\|ids\|info-get\|remove]
|
yes* |
deferred |
List[DeferredEvent] | local unit state db | yes |
stored_state |
List[StoredState] | local unit state db | yes |
model |
Model | envvars | no |
unit_id |
int | envvars | no |
containers |
List[Container] | (kubernetes only:) Pebble API | yes |
All data is readable according to the Juju access control rules: e.g. a follower unit cannot read its leader’s unit databag, nor write any databag other than its own.
See more: