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## Resource: Realtime Permissions Provider Service Plugin

## Article: Realtime Permissions Provider Service Plugin

## Article Link: https://dev.wix.com/docs/sdk/core-modules/realtime/extensions/realtime-permissions-provider/realtime-permissions-provider-service-plugin.md

## Article Content:

# Realtime Permissions Provider: Sample Flows

This article presents a possible use case and corresponding sample flow that you can support. It provides a useful starting point as you plan your implementation.

## Check permissions for a cross-app subscription

When a subscriber from another app attempts to subscribe to a channel managed by your app, Wix calls your Realtime Permissions service plugin to determine whether the subscriber can receive messages on that channel.

> **Note:** Your app must have a [Realtime Permissions Provider extension](https://dev.wix.com/docs/sdk/core-modules/realtime/extensions/realtime-permissions-provider/extension-config.md) with a deployment URI.

A cross-app subscription includes the following steps:

1. A site visitor or member on another app's site calls [Subscribe](https://dev.wix.com/docs/sdk/core-modules/realtime/realtime/subscriber/subscribe.md) with your app's `appId`, requesting to subscribe to one of your app's [channels or resources](https://dev.wix.com/docs/sdk/core-modules/realtime/realtime/introduction.md#channels-and-channel-resources). 

2. Wix calls [Check Subscriber Permissions](https://dev.wix.com/docs/sdk/core-modules/realtime/extensions/realtime-permissions-provider/check-subscriber-permissions.md) with details of the requested subscription, along with request metadata: 

    ```json
    {
      "request": {
        "channel": {
          "name": "premium-updates",
          "resourceId": "resource-456"
        },
        "subscriber": {
          "id": "2f8b9c1a-4e7d-4a3f-b6c8-9d0e1f2a3b4c",
          "type": "MEMBER"
        },
        "requestingAppId": "a1b2c3d4-e5f6-7890-abcd-ef1234567890"
      },
      "metadata": {
        "requestId": "12340987989.234092734777747",
        "identity": {
          "identityType": "MEMBER",
          "memberId": "2f8b9c1a-4e7d-4a3f-b6c8-9d0e1f2a3b4c"
        },
        "languages": ["en-US"]
      }
    }
    ```

3. Your service plugin applies your permissions logic. For example, the following implementation allows members and admins to subscribe to the `premium-updates` channel but denies visitors: 

    ```js
    import { realtimePermissionsProvider } from '@wix/realtime/service-plugins';

    realtimePermissionsProvider.provideHandlers({
      checkSubscriberPermissions: async (payload) => {
        const { request, metadata } = payload;
        const { channel, subscriber, requestingAppId } = request;

        // Use metadata for site-specific or locale-aware logic. Similarly, use requestingAppId to apply per-app authorization rules.

        // Only allow access to the "premium-updates" channel
        // for members and admins.
        if (channel.name === 'premium-updates') {
          return { read: subscriber.type !== 'VISITOR' };
        }

        // Allow all other channels by default.
        return { read: true };
      },
    });
    ```

    Learn more about [service plugin extensions](https://dev.wix.com/docs/build-apps/develop-your-app/extensions/backend-extensions/service-plugins/about-service-plugin-extensions.md).

    Your implementation must return an object with a `read` boolean. Return `true` to allow the subscription, or `false` to deny it:

    ```json
    {
      "read": true
    }
    ```

4. Wix applies the `read` value from your response. If `read` is `true`, the subscriber starts receiving messages on the channel. If `read` is `false`, Wix denies the subscription and the subscriber doesn't receive messages.

    > **Note:** If your handler throws an error, times out, or is unreachable, Wix denies the subscription with a 503 HTTP status code.