--- title: Charmhub | Deploy Istio using Charmhub - The Open Operator Collection description: Deploy the latest version of Istio as a Kubernetes Operator on any cloud. url: https://charmhub.io/istio-k8s/libraries/istio_metadata --- # Istio [Canonical Observability](https://charmhub.io/publisher/observability "View all packages from Canonical Observability") * [Canonical Observability](https://charmhub.io/publisher/observability "View all packages from Canonical Observability") Platform: 1.31/stable 82 ``` juju deploy istio-k8s --channel 1.31/stable ``` [Learn to deploy on juju >](https://juju.is/docs/juju/manage-applications) [Toggle side navigation](https://charmhub.io/istio-k8s/libraries/istio_metadata#drawer) ## charms.istio\_k8s.v0.istio\_metadata * [*Docstrings*Docstrings](https://charmhub.io/istio-k8s/libraries/istio_metadata) [*Code*Source code](https://charmhub.io/istio-k8s/libraries/istio_metadata/source-code) * + Download Fetch library ``` charmcraft fetch-lib charms.istio_k8s.v0.istio_metadata ``` [Download istio\_metadata.py](https://charmhub.io/istio-k8s/libraries/istio_metadata/download) + *Last updated* 10 Jul 2025 + *Revision* Library version 0.2 istio\_metadata. This library implements endpoint wrappers for the istio-metadata interface. The istio-metadata interface is used to transfer information about an instance of Istio, such as its root namespace. Typically, this is useful for charms that need details on how to interface with Istio. ##### Usage ###### Requirer IstioMetadataRequirer is a wrapper for pulling data from the istio-metadata interface. To use it in your charm: * observe the relation-changed and relation-broken events for this relation wherever your charm needs to use this data (this endpoint wrapper DOES NOT automatically observe any events) * wherever you need access to the data, call `IstioMetadataRequirer(...).get_data()` An example implementation is: ``` class FooCharm(CharmBase): def __init__(self, framework): super().__init__(framework) istio_metadata = IstioMetadataRequirer(self.model.relations, "istio-metadata") self.framework.observe(self.on["istio-metadata"].relation_changed, self._on_istio_metadata_changed) self.framework.observe(self.on["istio-metadata"].relation_broken, self._on_istio_metadata_changed) def _on_istio_metadata_changed(self): data = istio_metadata.get_data() ... ``` Where you also add relation to your `charmcraft.yaml` or `metadata.yaml` (note that IstioMetadataRequirer is designed for relating to a single application and must be used with limit=1 as shown below): ``` requires: istio-metadata: limit: 1 interface: istio_metadata ``` ###### Provider IstioMetadataProvider is a wrapper for publishing data to charms related using the istio-metadata interface. Note that `IstioMetadataProvider` *does not* manage any events, but instead provides a `publish` method for sending data to all related applications. Triggering `publish` appropriately is left to the charm author, although generally you want to do this at least during the `relation_joined` and `leader_elected` events. An example implementation is: ``` class FooCharm(CharmBase): def __init__(self, framework): super().__init__(framework) self.istio_metadata = IstioMetadataProvider( relation_mapping=self.model.relations, app=self.app, relation_name="istio-metadata", ) self.framework.observe(self.on.leader_elected, self.do_something_to_publish) self.framework.observe(self._charm.on["istio-metadata"].relation_joined, self.do_something_to_publish) self.framework.observe(self.on.some_event_that_changes_istio_metadata, self.do_something_to_publish) def do_something_to_publish(self, e): self.istio_metadata.publish(...) ``` Where you also add the following to your `charmcraft.yaml` or `metadata.yaml`: ``` provides: istio-metadata: interface: istio_metadata ``` --- Index * [class IstioMetadataAppData](https://charmhub.io/istio-k8s/libraries/istio_metadata#istiometadataappdata) * [class IstioMetadataRequirer](https://charmhub.io/istio-k8s/libraries/istio_metadata#istiometadatarequirer) * + [def \_\_init\_\_( self, relation\_mapping, relation\_name)](https://charmhub.io/istio-k8s/libraries/istio_metadata#istiometadatarequirer-__init__) * + [def relations( self)](https://charmhub.io/istio-k8s/libraries/istio_metadata#istiometadatarequirer-relations) * + [def get\_data( self)](https://charmhub.io/istio-k8s/libraries/istio_metadata#istiometadatarequirer-get_data) * [class IstioMetadataProvider](https://charmhub.io/istio-k8s/libraries/istio_metadata#istiometadataprovider) * + [def \_\_init\_\_( self, charm, relation\_mapping, app, relation\_name)](https://charmhub.io/istio-k8s/libraries/istio_metadata#istiometadataprovider-__init__) * + [def relations( self)](https://charmhub.io/istio-k8s/libraries/istio_metadata#istiometadataprovider-relations) * + [def publish( self, root\_namespace)](https://charmhub.io/istio-k8s/libraries/istio_metadata#istiometadataprovider-publish) #### class IstioMetadataAppData Description Data model for the istio-metadata interface. None #### class IstioMetadataRequirer Description Endpoint wrapper for the requirer side of the istio-metadata relation. None Methods IstioMetadataRequirer. \_\_init\_\_( *self* , relation\_mapping: RelationMapping , relation\_name: str ) Initialize the IstioMetadataRequirer object. Arguments relation\_mapping The RelationMapping of a charm (typically `self.model.relations` from within a charm object). relation\_name The name of the wrapped relation. Description This object is for accessing data from relations that use the istio-metadata interface. It **does not** autonomously handle the events associated with that relation. It is up to the charm using this object to observe those events as they see fit. Typically, that charm should observe this relation's relation-changed event. This object is for interacting with a relation that has limit=1 set in charmcraft.yaml. In particular, the get\_data method will raise if more than one related application is available. IstioMetadataRequirer. relations( *self* ) Description Return the relation instances for applications related to us on the monitored relation. None IstioMetadataRequirer. get\_data( *self* ) Return data for at most one related application, raising if more than one is available. Description Useful for charms that always expect exactly one related application. It is recommended that those charms also set limit=1 for that relation in charmcraft.yaml. Returns None if no data is available (either because no applications are related to us, or because the related application has not sent data). #### class IstioMetadataProvider Description The provider side of the istio-metadata relation. None Methods IstioMetadataProvider. \_\_init\_\_( *self* , charm: CharmBase , relation\_mapping: RelationMapping , app: Application , relation\_name: str ) Initialize the IstioMetadataProvider object. Arguments charm The charm instantiating this object. relation\_mapping The RelationMapping of a charm (typically `self.model.relations` from within a charm object). app This application. relation\_name The name of the relation. Description This object is for serializing and sending data to a relation that uses the istio-metadata interface - it does not automatically observe any events for that relation. It is up to the charm using this to call publish when it is appropriate to do so, typically on at least the charm's leader\_elected event and this relation's relation\_joined event. IstioMetadataProvider. relations( *self* ) Description Return the applications related to us under the monitored relation. None IstioMetadataProvider. publish( *self* , root\_namespace: str ) Post istio-metadata to all related applications. Arguments root\_namespace The root namespace of the Istio deployment. Description This method writes to the relation's app data bag, and thus should never be called by a unit that is not the leader otherwise ops will raise an exception.