Trigger replication on changes

By default RxDB will periodically sync from the remote GraphQL source. This time interval for the sync to be triggered can be set by using the liveInterval parameter. In this example we have set it to 10 minutes. However, we can also use a GraphQL subscription so that Hasura notifies us as soon as there is a change and trigger replication manually. This is done by the setupGraphQLSubscription method of the GraphQLReplicator class.

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setupGraphQLSubscription(auth, replicationState) {
    // Change this url to point to your hasura graphql url
    const endpointURL = 'wss://my-hasura-instance.hasura.app/v1/graphql'; 
    
    const wsClient = new SubscriptionClient(endpointURL, {
        reconnect: true,
        connectionParams: {
            headers: {
                'Authorization': `Bearer ${auth.idToken}`
            }
        },
        timeout: 1000 * 60,
        onConnect: () => {
            console.log('SubscriptionClient.onConnect()');
        },
        connectionCallback: () => {
            console.log('SubscriptionClient.connectionCallback:');
        },
        reconnectionAttempts: 10000,
        inactivityTimeout: 10 * 1000,
        lazy: true
    });

    const query = `subscription onTodoChanged {
        todos {
            id
            deleted
            isCompleted
            text
        }       
    }`;

    const ret = wsClient.request({ query });

    ret.subscribe({
        next(data) {
            console.log('subscription emitted => trigger run');
            console.dir(data);
            replicationState.run();
        },
        error(error) {
            console.log('got error:');
            console.dir(error);
        }
    });

    return wsClient
}    

The above code uses Apollo subscription client to subscribe to changes on the todos table from hasura. It then triggers replication whenever new data is received.