State service
- Concept
- 3 minutes
The state service provides a key-value storage for your app to store internal states.
It can store essential data needed for the app's functioning in its context. Data access is configurable: either to all users or confined to a specific user's context. These states are only accessible from their respective apps and can't be accessed using a different app or ad-hoc functions.
If the data set is extensive (see Limitations) or multiple users need to collaborate on the data, the document service may be a better fit.
Concepts
You need to know the following concepts to work with the state service.
User app states
You can use user app states to store information that is relevant only to a specific user and app context. For example, the configurable state of components that are used in your app. User app states persist across that user's sessions and devices.
App states
Be aware that all app users can read app states. If your use case allows for a user-scoped state, best practice is to use the the user app state.
App states are accessible to all users; therefore, you can share specific states essential to the app's context. For example, you can create a workflow that fetches third-party data into your app function. Your app stores this information in its app state. All users of your app can then access this data.
There are also use cases for writing an app state in browser code. For example, the app can allow the user to share some meta information (that is only relevant in the context of this app) with other users.
Limitations
Generic key-value-based state storage, where the key and value are simple strings, allows you to manage the state design according to your app's specific needs.
For example, instead of using multiple small chunks of state, you can use one more significantly larger state as an alternative. The limits the app must abide by for either case are listed below.
- User app states: Each user is allowed up to 16 states per app. User app state values must not exceed 32 KB. User app state keys must not exceed 200 characters.
- App states: A single app state value must not exceed 10 MB. The sum of all app state values for a single app must not exceed 50 MB. An app state key must not exceed 200 characters.
Any operation violating these limits will result in an error. You can delete states to avoid imminent quota violations.
Reset states
Administrators (users with the policy "AppEngine - Admin") can clear all app states and user app states of an app in the by selecting the Reset state context menu entry. In addition, any user can also trigger the clearance of their user app states.