How to store app data

Apps usually have configuration data that can be changed by the user during runtime:

• access keys to the external APIs (e.g. a key to a payment gateway)
• preferences like how the app should look (e.g. customized messages)
• optional features which can be turned off or on (e.g. if an additional notification should be sent to the user)

Depending on the type of app you are creating, you might need a dedicated database for such data. However, in most cases, a simpler solution will be perfectly fine.

A solution built-in in Saleor is privateMetadata.

What is Metadata and what are its features

Apps are one of the classes implementing ObjectWithMetadata interface, which can be used to store additional data in the Saleor database.

privateMetadata field in the app object can be accessed only by the app itself or the users with MANAGE_APPS permission. The field returns a list of key and value pairs that can contain any string, including stringified JSON.

From the app developer's perspective there are a few pros in using it:

• you don't need additional infrastructure to keep the data
• it plays well with the multi-tenant approach; each registered Saleor instance has its own preferences
• when the app is uninstalled, the data is automatically removed

Using the Metadata

You can access the API directly, or use the utils provided by the SDK.

With GraphQL API

To get private metadata, run the query:

query {
  app {
    privateMetadata {
      key
      value
    }
  }
}

ID argument

If you run the query with the app registration token, you don't need to specify the ID argument in the app query.

Which will return:

{
  "data": {
    "app": {
      "privateMetadata": [
        {
            "key": "Example key",
            "value": "example value"
        }
      ]
    }
  },

Setting new keys or updating the existing ones:

mutation {
  updateMetadata(
    id: "QXBwOjE3OA=="
    input: [{ key: "new metadata", value: "example value" }]
  ) {
    errors {
      field
      message
    }
  }
}

With App SDK MetadataManager

note

The full documentation of the manager can be found in the App SDK docs.

Using this abstraction will give you a nicer interface to interact with and additional caching to improve performance.

Entries in the manager are stored using the structure:

  key: string;
  value: string;
  domain?: string;

Optional domain field

Since metadata will be copied if you clone the database of your Saleor instance, we recommend adding the parameter domain to prevent misusing secret keys from different domains.

Interacting with the API is done with the methods:

• get: (key: string, domain?: string) => Promise<string | undefined>
• set: (settings: SettingsValue[] | SettingsValue) => Promise<void>

EncryptedMetadataManager

If you want to keep secrets, like non-public API keys, we recommend using EncryptedMetadataManager. It will encrypt the values for the additional layer of security. get and set methods have the same interface.

note

If you prefer to see the managers in action, there is an example repository which comes with UI implementation and API endpoints.