Subscriptions

Realtime sync to your database collections

To subscribe to any collection in a Hasura server with dynamic parameters using GraphQL subscriptions, you can use JavaScript and the graphql-ws library. This setup allows you to receive real-time updates for a generic collection specified by the user, with dynamic filtering criteria.

First, ensure you have the necessary dependencies installed. If they aren't already set up, you can install them with npm or yarn:

npm install graphql graphql-ws

Next, create a JavaScript file that establishes a WebSocket connection and sets up subscriptions to a specified collection with dynamic parameters:

const { createClient } = require('graphql-ws');

const client = createClient({
  url: 'wss://your-hasura-instance.uncodie.com/v1/graphql',
  connectionParams: {
    headers: {
      'Authorization': 'Bearer your-access-token'
    }
  }
});

// Replace `collection_name` with your actual collection name
const collectionName = 'your_collection_name';

const query = `
  subscription getCollectionData($filter: your_filter_type!) {
    ${collectionName}(where: $filter) {
      field1
      field2
      // Add more fields as needed
    }
  }
`;

// Define your dynamic filter here, adjust `your_filter_type` to match your schema
const variables = {
  filter: {
    dynamicField: { _eq: "dynamicValue" }
  }
};

client.subscribe(
  { query, variables },
  {
    next(data) {
      console.log('Data received:', data);
    },
    error(err) {
      console.error('Error:', err);
    },
    complete() {
      console.log('Subscription complete');
    },
  }
);

Replace 'wss://your-hasura-instance.uncodie.com/v1/graphql' with the URL of your Hasura instance and adjust 'your-access-token' with your API access token. Modify your_collection_name and your_filter_type according to the specific collection and filtering criteria you need to use. The dynamicField and dynamicValue in the variables object should be replaced with the actual field and value you want to filter by.

This script dynamically subscribes to updates from any specified collection and filters based on the provided criteria. Whenever there is a change in the database that meets these filters, you will receive notifications through the WebSocket, and the next function will be triggered to handle the incoming data.

Adjust the query and variables as necessary to align with your Hasura schema's specific details and the data fields you need to monitor. This approach allows for great flexibility in handling various collections and dynamic querying conditions.