Guide to Polling in React Query

React Query is a powerful tool for managing server state in React applications. Polling with React Query enables continuous data fetching at specified intervals, ensuring that the application's data remains fresh and up-to-date. This guide covers everything you need to know about it.

What is polling in React Query?

Polling is a technique where a data fetching operation is executed repeatedly at regular intervals. This is particularly useful in applications where real-time data updates are crucial. React Query's polling mechanism is straightforward to implement and manage.

How to set up polling in React Query

To set up polling, use the useQuery hook with the refetchInterval option. This option accepts a number representing the interval in milliseconds.

import { useQuery } from 'react-query';

const fetchData = async () => {
    // Fetch data logic
};

const Component = () => {
    const { data, isLoading, error } = useQuery('dataKey', fetchData, {
        refetchInterval: 2000, // Poll every 2000ms
    });

    // Component logic
};

How to control polling in React Query

React Query offers several options to control the polling behavior:

• refetchIntervalInBackground: Set this to true to continue polling even when the browser window is not focused.
• enabled: Control whether the query is enabled or disabled. Polling will only occur when the query is enabled.
• refetchOnWindowFocus: Automatically refetch data when the window regains focus.

const { data } = useQuery('dataKey', fetchData, {
    refetchInterval: 2000,
    refetchIntervalInBackground: true,
    enabled: true,
    refetchOnWindowFocus: true
});

How to optimize polling in React Query

To prevent unnecessary network requests and optimize your application, consider the following strategies:

• Use staleTime to specify how long data is considered fresh, reducing the frequency of refetches.
• Implement onSuccess and onError callbacks to handle successful and failed fetches, respectively.
• Combine polling with query caching to minimize the impact on performance.

const { data } = useQuery('dataKey', fetchData, {
    refetchInterval: 2000,
    staleTime: 5000,
    onSuccess: (data) => {
        // Handle successful fetch
    },
    onError: (error) => {
        // Handle error
    }
});

Handling background updates

When implementing polling in an application that runs in the background, it's crucial to manage network and CPU usage. Use refetchIntervalInBackground judiciously and consider reducing the polling frequency when the application is not in focus.