Event '<relation name>-relation-created'

Event > List of events> Relation events > <relation name>-relation-created

See also: A charm’s life, The lifecycle of charm relations, Discussion on hooks: relation-departed and relation-broken, Relation-broken hook not running in peers relation, Charm hooks

Before juju v.3.0, ‘integrations’ were called ‘relations’. Remnants of this persist in the names, options, and output of certain commands, and in integration event names.

relation-created is a “setup” event and, emitted when an application is related to another. Its purpose is to inform the newly related charms that they are entering the relation.

If juju is aware of the existence of the relation “early enough”, before the application has started (i.e. before the application has started = start has run), this event will be fired as part of the Setup phase. An important consequence of this fact is, that for all peer-type relations, since juju is aware of their existence from the start, those relation-created events will always fire before start.

Similarly, if an application is being scaled up, the new unit will see relation-created events for all relations the application already has during the Setup phase.

Contents:

Emission sequence

Scenario Example Command Resulting Events
Integrate juju integrate foo bar (all foo & bar units): *-relation-created --> *-relation-joined -> *-relation-changed
Scale up an integrated app juju add-unit -n1 foo (new foo unit): install -> *-relation-created -> leader-settings-changed -> config-changed -> start

In the following scenario, one deploys two applications and relates them “very early on”. For example, in a single command.

Scenario Example Command Resulting Events
Deploy and quickly integrate juju deploy foo; juju deploy bar; juju integrate foo bar (all units): same as previous case.

Relation Data

Starting from when *-relation-created is received, relation data can be read-written by units, up until when the corresponding *-relation-broken is received.

Observing this event in Ops

In Ops, you can observe the event like you would any other:
self.framework.observe(
    charm.on.<relation name>_relation_created, 
    self._on_<relation name>_relation_created
)

The RelationCreatedEvent event object does not expose any specific attributes.

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