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## Summary Updates a number of broken file references and broken links. --------- Co-authored-by: kibanamachine <42973632+kibanamachine@users.noreply.github.com> Co-authored-by: Alejandro Fernández Haro <afharo@gmail.com>
88 lines
6.1 KiB
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88 lines
6.1 KiB
Text
---
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id: kibDevDocsPersistableStateIntro
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slug: /kibana-dev-docs/key-concepts/persistable-state-intro
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title: Persistable State
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description: Persitable state is a key concept to understand when building a Kibana plugin.
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date: 2021-02-02
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tags: ['kibana', 'dev', 'contributor', 'api docs']
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---
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“Persistable state” is developer-defined state that supports being persisted by a plugin other than the one defining it. Persistable State needs to be serializable and the owner can/should provide utilities to migrate it, extract and inject any <DocLink id="kibDevDocsSavedObjectsIntro" section="references" text="references to Saved Objects"/> it may contain, as well as telemetry collection utilities.
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## Exposing state that can be persisted
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Any plugin that exposes state that another plugin might persist should implement <DocLink id="kibKibanaUtilsPluginApi" section="def-common.PersistableStateService" text="`PersistableStateService`"/> interface on their `setup` contract. This will allow plugins persisting the state to easily access migrations and other utilities.
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Example: Data plugin allows you to generate filters. Those filters can be persisted by applications in their saved
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objects or in the URL. In order to allow apps to migrate the filters in case the structure changes in the future, the Data plugin implements `PersistableStateService` on <DocLink id="kibDataQueryPluginApi" section="def-public.FilterManager" text="`data.query.filterManager`"/>.
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note: There is currently no obvious way for a plugin to know which state is safe to persist. The developer must manually look for a matching `PersistableStateService`, or ad-hoc provided migration utilities (as is the case with Rule Type Parameters).
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In the future, we hope to make it easier for producers of state to understand when they need to write a migration with changes, and also make it easier for consumers of such state, to understand whether it is safe to persist.
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## Exposing state that can be persisted but is not owned by plugin exposing it (registry)
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Any plugin that owns collection of items (registry) whose state/configuration can be persisted should implement `PersistableStateService`
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interface on their `setup` contract and each item in the collection should implement <DocLink id="kibKibanaUtilsPluginApi" section="def-common.PersistableStateDefinition" text="`PersistableStateDefinition`"/> interface.
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Example: Embeddable plugin owns the registry of embeddable factories to which other plugins can register new embeddable factories. Dashboard plugin
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stores a bunch of embeddable panels input in its saved object and URL. Embeddable plugin setup contract implements `PersistableStateService`
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interface and each `EmbeddableFactory` needs to implement `PersistableStateDefinition` interface.
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Embeddable plugin exposes this interfaces:
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```
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// EmbeddableInput implements Serializable
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export interface EmbeddableRegistryDefinition extends PersistableStateDefinition<EmbeddableInput> {
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id: string;
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...
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}
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export interface EmbeddableSetup extends PersistableStateService<EmbeddableInput>;
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```
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Note: if your plugin doesn't expose the state (it is the only one storing state), the plugin doesn't need to implement the `PersistableStateService` interface.
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If the state your plugin is storing can be provided by other plugins (your plugin owns a registry) items in that registry still need to implement `PersistableStateDefinition` interface.
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## Storing persistable state as part of saved object
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Any plugin that stores any persistable state as part of their saved object should make sure that its saved object migration
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and reference extraction and injection methods correctly use the matching `PersistableStateService` implementation for the state they are storing.
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Take a look at [example saved object](https://github.com/elastic/kibana/blob/8.9/examples/embeddable_examples/server/searchable_list_saved_object.ts#L32) which stores an embeddable state. Note how the `migrations`, `extractReferences` and `injectReferences` are defined.
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## Storing persistable state as part of URL
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When storing persistable state as part of URL you must make sure your URL is versioned. When loading the state `migrateToLatest` method
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of `PersistableStateService` should be called, which will migrate the state from its original version to latest.
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note: Currently there is no recommended way on how to store version in url and its up to every application to decide on how to implement that.
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## Available state operations
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### Extraction/Injection of References
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In order to support import and export, and space-sharing capabilities, Saved Objects need to explicitly list any references they contain to other Saved Objects.
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To support persisting your state in saved objects owned by another plugin, the <DocLink id="kibKibanaUtilsPluginApi" section="def-common.PersistableState.extract" text="`extract`"/> and <DocLink id="kibKibanaUtilsPluginApi" section="def-common.PersistableState.inject" text="`inject`"/> methods of Persistable State interface should be implemented.
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<DocLink
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id="kibDevTutorialSavedObject"
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section="references"
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text="Learn how to define Saved Object references"
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/>
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[See example embeddable providing extract/inject functions](https://github.com/elastic/kibana/blob/8.9/examples/embeddable_examples/public/migrations/migrations_embeddable_factory.ts)
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### Migrations and Backward compatibility
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As your plugin evolves, you may need to change your state in a breaking way. If that happens, you should write a migration to upgrade the state that existed prior to the change.
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<DocLink id="kibDevTutorialSavedObject" section="migrations" text="How to write a migration" />.
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[See an example saved object storing embeddable state implementing saved object migration function](https://github.com/elastic/kibana/blob/8.9/examples/embeddable_examples/server/searchable_list_saved_object.ts)
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[See example embeddable providing migration functions](https://github.com/elastic/kibana/blob/8.9/examples/embeddable_examples/public/migrations/migrations_embeddable_factory.ts)
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## Telemetry
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You might want to collect statistics about how your state is used. If that is the case you should implement the telemetry method of Persistable State interface.
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