Axios interceptor to retry sending FormData

ONLINECAST

2 min read

·

06-10-2024

10

0

Share

Mastering Axios Interceptors: Efficiently Retrying FormData Submissions

Problem: Imagine you're building an application that allows users to upload files. You're using Axios to send the FormData to your server, but sometimes network issues or other unforeseen circumstances can lead to the request failing. How can you automatically retry these requests to ensure the upload is successful without manual intervention?

The Solution: Axios Interceptors to the rescue! These powerful tools allow you to intercept and modify requests and responses before they reach your application code. Let's explore how to leverage them to gracefully retry FormData uploads.

Understanding the Challenge

Here's a typical scenario:

const formData = new FormData();
formData.append('file', fileInput.files[0]);

axios.post('/upload', formData)
  .then(response => {
    // Success!
  })
  .catch(error => {
    // Handle the error 
  });

While this works, it doesn't account for potential network hiccups. If the upload fails, the user might experience frustration and have to manually retry. Let's fix this with interceptors.

The Power of Axios Interceptors

Axios interceptors allow you to:

• Modify Requests: Add headers, manipulate data, or even cancel a request before it's sent.
• Handle Responses: Modify data, check for errors, or transform the response.

Here's how to implement a retry mechanism:

// Create a function to retry the request
const retryRequest = (config, error) => {
  const retryCount = config.retryCount || 0;

  // Maximum retries (e.g., 3 attempts)
  if (retryCount > 3) {
    // Final error handling
    return Promise.reject(error);
  }

  // Increase the retry count
  config.retryCount = retryCount + 1;

  // Wait for a certain time before retrying
  return new Promise((resolve) => {
    setTimeout(() => {
      resolve(axios(config));
    }, 1000); // Retry after 1 second
  });
};

// Define the Axios interceptor
axios.interceptors.request.use(
  config => {
    // Add retryCount property to track attempts
    if (config.data instanceof FormData) {
      config.retryCount = 0;
    }
    return config;
  },
  error => {
    return Promise.reject(error);
  }
);

// Define the retry interceptor
axios.interceptors.response.use(
  response => {
    return response;
  },
  error => {
    // Only retry for FormData requests
    if (error.config.data instanceof FormData) {
      return retryRequest(error.config, error);
    }

    return Promise.reject(error);
  }
);

// Send the FormData
const formData = new FormData();
formData.append('file', fileInput.files[0]);

axios.post('/upload', formData)
  .then(response => {
    // Success!
  })
  .catch(error => {
    // Handle the final error after retrying
  }); 

Explanation:

1. retryRequest function: This function takes the request configuration and the error as arguments. It checks if the retry count has exceeded the maximum, handles final errors, and uses setTimeout to delay the retry attempt.
2. Request Interceptor: We add a retryCount property to the configuration object for FormData requests.
3. Response Interceptor: If the response is an error and the data was FormData, the retryRequest function is called.
4. Error Handling: Make sure to handle the final error after the retries have been exhausted.

Key Points:

• Customization: Adjust the retry count, delay time, and error handling logic to fit your specific needs.
• Network Considerations: Be mindful of potential backoff strategies to prevent flooding the server with too many requests.
• User Feedback: Inform users about the retry attempts to maintain transparency.

Beyond the Basics

Interceptors can be used for various tasks, like:

• Authentication: Add authentication tokens to every request.
• Logging: Log every request and response for debugging.
• Error Handling: Centralized error handling across your application.

By mastering Axios interceptors, you can dramatically improve the reliability and user experience of your application, especially when dealing with potentially unreliable network connections.