Managing Non-Error Promise Rejections Following Invisible reCAPTCHA v3 Integration on Google Cloud Platform

Challenges in Managing Promise Rejections with reCAPTCHA v3 in React Applications

Integrating Google’s invisible reCAPTCHA v3 into a React application provides an extra layer of security, helping to prevent malicious bot activity. However, new issues can emerge after deployment, as developers may encounter unexpected errors. One such problem that developers face is the , which can be particularly frustrating to debug.

After releasing a new version of an application, developers may notice error reports in their Sentry dashboards, such as an error with the message "Non-Error promise rejection captured with value: Timeout." This specific issue can complicate user interactions, particularly for those already logged into the application but not directly interacting with reCAPTCHA.

In this case, while reCAPTCHA was successfully integrated and applied on the login page, errors still surfaced during non-login interactions. It raises questions about why a timeout error related to reCAPTCHA appears when the user isn’t actively going through the login process. Understanding the cause of these issues requires a deep dive into how the is loaded and managed across different parts of the app.

This article will explore the underlying causes of this error, examine potential solutions, and offer best practices for handling promise rejections in React apps, particularly when working with Google Cloud services like reCAPTCHA v3.

Command	Example of use
useEffect()	A React hook used for running side effects in function components. In the context of reCAPTCHA, it's used to load and execute the reCAPTCHA when the component is mounted.
loadReCaptcha()	Loads the reCAPTCHA library asynchronously. This is critical when using Webpack to ensure the script is loaded correctly for token generation.
executeReCaptcha()	Executes the invisible reCAPTCHA to generate a token for verification. This function runs the challenge on the client side.
axios.post()	Used to send a POST request to the Google reCAPTCHA API for token verification. The POST request includes the reCAPTCHA token and secret key.
timeout: 5000	Sets a 5-second timeout for the reCAPTCHA API request to avoid hanging requests and handle server response delays.
response.data.success	Checks the success status returned from the Google reCAPTCHA API, indicating whether the token verification was successful or not.
response.data['error-codes']	Accesses error codes returned by the Google reCAPTCHA API when token validation fails, useful for debugging specific failures.
ECONNABORTED	An error code in Node.js indicating that the request has been aborted due to a timeout, used to specifically handle cases where the reCAPTCHA API doesn’t respond in time.
setError()	A React state setter function to store error messages in the component's state, allowing for more robust error handling in the front-end reCAPTCHA process.

In-Depth Analysis of Handling reCAPTCHA Promise Rejections in React Applications

The front-end script begins by utilizing React’s hook, which is essential for executing side effects, such as loading external libraries. In this case, the reCAPTCHA library is loaded when the component mounts. The function is called to ensure the reCAPTCHA script is available for token generation, a crucial step since this feature isn't needed for the entire app but only for specific pages like the login. By placing this code within useEffect, the script executes once when the page loads, efficiently managing script loading.

Once the script is loaded, the function is used to trigger the token generation process. This function sends the invisible challenge to the user’s browser, generating a token that is used to verify user authenticity. If the token generation fails, the error is caught and set in the component’s state using the function. This structure allows developers to handle errors effectively without disrupting the user experience, displaying appropriate error messages when necessary. The token is then returned for further use in login or other processes.

On the backend, a Node.js script is employed to handle token validation. The command is used to send a POST request to Google's reCAPTCHA API. The token received from the front end, along with the secret key, is included in the request. If the token is valid, the API responds with a success flag, which is checked using . This method ensures that only valid tokens allow the user to proceed, adding an extra layer of security to the login process. A 5-second timeout is configured in the axios request to prevent the server from waiting indefinitely.

If the API request fails or takes too long to respond, the error code is used to handle the timeout specifically. This is important because timeouts can often lead to unhandled promise rejections, as seen in the original problem. The backend script catches these errors, logs them, and returns appropriate error messages to the client. This detailed error handling, including timeout management, ensures that the application doesn’t fail silently and provides better insights into potential issues with the reCAPTCHA service or network delays.

// Step 1: Load reCAPTCHA using Webpack
import { useState, useEffect } from 'react';
import { loadReCaptcha, executeReCaptcha } from 'recaptcha-v3';

// Step 2: Add hook to manage token and errors
const useReCaptcha = () => {
  const [token, setToken] = useState(null);
  const [error, setError] = useState(null);

  useEffect(() => {
    const loadCaptcha = async () => {
      try {
        await loadReCaptcha();
        const result = await executeReCaptcha('login');
        setToken(result);
      } catch (err) {
        setError('Failed to load reCaptcha or capture token.');
      }
    };
    loadCaptcha();
  }, []);
  return { token, error };
};

// Step 3: Call token function in login form
const LoginForm = () => {
  const { token, error } = useReCaptcha();
  if (error) console.error(error);

  const handleSubmit = async (event) => {
    event.preventDefault();
    // Send token and form data to backend
    if (token) {
      // Add logic to submit form
    } else {
      alert('ReCaptcha validation failed');
    }
  };

  return (
    <form onSubmit={handleSubmit}>
      <input type="submit" value="Submit"/>
    </form>
  );
};

// Step 1: Import axios for API call and configure environment variables
const axios = require('axios');
const RECAPTCHA_SECRET = process.env.RECAPTCHA_SECRET;

// Step 2: Create token verification function
const verifyReCaptcha = async (token) => {
  try {
    const response = await axios.post(
      'https://www.google.com/recaptcha/api/siteverify',
      `secret=${RECAPTCHA_SECRET}&response=${token}`,
      { timeout: 5000 } // 5-second timeout
    );

    if (response.data.success) {
      return { success: true, score: response.data.score };
    } else {
      return { success: false, errorCodes: response.data['error-codes'] };
    }
  } catch (error) {
    if (error.code === 'ECONNABORTED') {
      throw new Error('reCAPTCHA request timed out');
    }
    throw new Error('Error verifying reCAPTCHA token');
  }
};

// Step 3: Validate the token in your route
app.post('/login', async (req, res) => {
  const token = req.body.token;
  if (!token) {
    return res.status(400).json({ error: 'No token provided' });
  }
  try {
    const result = await verifyReCaptcha(token);
    if (result.success) {
      res.json({ message: 'Login successful', score: result.score });
    } else {
      res.status(401).json({ error: 'reCAPTCHA failed', errors: result.errorCodes });
    }
  } catch (error) {
    res.status(500).json({ error: error.message });
  }
});

Ensuring Robust reCAPTCHA Integration Across Multiple Pages

One key aspect often overlooked when implementing reCAPTCHA in a React application is managing the reCAPTCHA script across multiple pages or routes. While reCAPTCHA might be implemented for specific functionalities like login, the script is often loaded globally, which can lead to unnecessary resource usage or errors such as the captured with value: Timeout. This typically occurs when users navigate to other parts of the app where reCAPTCHA isn't needed, but the script is still active.

A common solution to this problem is to conditionally load the reCAPTCHA script only on the pages that require it. Instead of bundling the script for the entire application, developers can dynamically import the script using React’s lazy loading or async loading methods. This reduces the potential for errors, like the timeout issue in routes that don’t use reCAPTCHA. By limiting the scope of where the script runs, performance improves and unexpected errors are minimized.

Another consideration is the lifecycle management of the reCAPTCHA instance. When the reCAPTCHA script is loaded globally, it can stay active even after navigating away from the login page, leading to or stale tokens. To avoid this, it’s essential to ensure that reCAPTCHA instances are properly cleaned up when users navigate to different routes, preventing stale requests and unnecessary API calls.

1. What causes the Non-Error promise rejection in reCAPTCHA v3?
2. The error typically occurs due to the reCAPTCHA script timing out or failing to generate a token in non-login routes. To avoid this, ensure that the command is called only on required pages.
3. Can I load the reCAPTCHA script only on certain routes in a React app?
4. Yes, by using React’s lazy loading or dynamic imports, you can conditionally load the reCAPTCHA script only on the necessary routes, improving performance.
5. How can I handle reCAPTCHA token timeouts?
6. You can manage timeouts by setting a specific timeout using when sending the token to the backend for validation, preventing infinite waits.
7. Why does the reCAPTCHA script stay active after navigating away from the login page?
8. This happens when the script is globally loaded. Make sure to clean up the reCAPTCHA instance by using appropriate React lifecycle methods.
9. What’s the best way to handle reCAPTCHA errors in production?
10. Use React state management to track errors and display meaningful messages when the function is triggered. This helps manage issues like token failures gracefully.

Integrating reCAPTCHA v3 with React can introduce unexpected challenges, particularly when promise rejections occur due to timeout issues. Proper script management and conditional loading help address these problems effectively.

By optimizing both the front-end and back-end handling of reCAPTCHA, developers can ensure better performance, security, and user experience across different routes of the application, even for logged-in users not directly interacting with reCAPTCHA.