How to return an error but continue to retry in react- query

When using React Query, we can leverage its automatic retry functionality to handle failed requests. React Query defaults to retrying failed requests, especially when failures are caused by network issues or server problems. We can control this behavior by configuring the retry strategy, including the number of retries and retry intervals.

1. Configuring Retry Count

We can specify the number of retries by passing the retry parameter when using useQuery or useMutation. For example:

javascript
import { useQuery } from 'react-query';

const fetchUserData = async () => {
  const response = await fetch('/api/user');
  if (!response.ok) {
    throw new Error('Network response was not ok');
  }
  return response.json();
};

const { isLoading, error, data } = useQuery('userData', fetchUserData, {
  retry: 3,  // If the request fails, retry up to 3 times
});

In this example, if the request to /api/user fails, React Query will automatically retry up to three times.

2. Custom Retry Logic

In addition to setting a fixed number of retries, we can define more complex retry logic by passing a function. This function takes two parameters: failureCount (the number of failures) and error (the error object), and returns a boolean indicating whether to continue retrying based on these parameters.

javascript
const { isLoading, error, data } = useQuery('userData', fetchUserData, {
  retry: (failureCount, error) => {
    // Retry only on specific error codes
    if (error.status === 503) {  // For example, retry only when the server returns a 503 Service Unavailable status
      return true;
    } else {
      return false;
    }
  }
});

3. Configuring Retry Delay

We can configure the delay between retries using the retryDelay parameter. This parameter can be a fixed millisecond value or a function that returns the delay time based on the retry attempt.

javascript
const { isLoading, error, data } = useQuery('userData', fetchUserData, {
  retry: 3,
  retryDelay: retryAttempt => Math.min(1000 * 2 ** retryAttempt, 30000)  // Exponential backoff strategy
});

In this example, if the request fails, the retry delay will be exponentially increasing but capped at 30 seconds.

Through these configurations, React Query provides flexible and powerful ways to handle and optimize failed requests caused by network issues or other reasons, thereby improving the robustness and user experience of the application. When using React Query, if your request fails, you might want to automatically retry it, which is very useful for handling unstable networks or data synchronization failures. React Query provides highly flexible retry strategies that can be configured in various ways.

Basic Usage

By default, React Query retries failed requests up to three times. This is the library's default setting, and you don't need additional configuration to benefit from it. This default behavior can be overridden in individual queries or globally configured.

Custom Retry Count

You can customize the number of retries by setting the retry option. For example, if you want a query to retry up to five times on failure, you can set it as:

javascript
useQuery('todos', fetchTodos, {
  retry: 5
});

Advanced Retry Strategy

In addition to setting a fixed number of retries, React Query allows you to define a retry strategy function that decides whether to retry based on the number of failures and error type.

For example, if you want to retry only on specific errors, you can do:

javascript
useQuery('todos', fetchTodos, {
  retry: (failureCount, error) => {
    // Retry only when the error is a network error
    if (error.status === 504) {
      return true;
    }
    return false;
  }
});

Delayed Retries

Sometimes, immediately retrying may not be a good choice, especially when the server is under heavy load or undergoing maintenance. React Query allows you to set the delay between retries using the retryDelay option. This option can be a fixed time (in milliseconds) or a function that returns a dynamically calculated delay.

javascript
useQuery('todos', fetchTodos, {
  retry: 4,
  retryDelay: (attemptIndex) => Math.min(1000 * 2 ** attemptIndex, 30000)
});

In this example, the retry delay uses an exponential backoff strategy, where the waiting time increases with each retry but is capped at 30 seconds.

Summary

Using React Query's retry mechanism can help you build more robust data fetching logic. With flexible configuration options, you can easily adjust retry behavior based on specific scenarios, whether it's simple retries with a fixed count or complex strategies based on error types and failure counts. This can significantly improve the user experience and data consistency of your application.