NodeJS Fetch: Handle Network Error Type on same fetch request

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29-09-2024

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Mastering Node.js Fetch: Handling Network Error Types on the Same Request

You've encountered a common challenge in Node.js development: how to gracefully handle different types of network errors within a single fetch request. This article explores the solution, empowering you to build more robust and responsive Node.js applications.

The Problem: Network Error Types

Imagine you're fetching data from an API using Node.js's fetch function:

const fetch = require('node-fetch');

async function fetchData() {
  try {
    const response = await fetch('https://api.example.com/data');
    const data = await response.json();
    console.log(data);
  } catch (error) {
    console.error('Error fetching data:', error);
  }
}

fetchData();

This code gracefully handles any error thrown during the fetch process. However, it provides limited insight into the specific error type.

Possible Network Errors:

• Connection Refused: The server might not be reachable, leading to a ECONNREFUSED error.
• Timeout: The server might not respond within the set timeout, resulting in a ETIMEDOUT error.
• Network Issue: A temporary network glitch might interrupt the connection, causing an EHOSTUNREACH or ENETUNREACH error.
• Server Error: The server might return an HTTP error code (e.g., 404 Not Found, 500 Internal Server Error).

The Challenge: Distinguishing between these different network errors is crucial for providing meaningful feedback to the user and implementing appropriate retry strategies.

The Solution: Fine-Grained Error Handling

To handle specific network error types, we leverage the response object returned by the fetch function. Here's the updated code:

const fetch = require('node-fetch');

async function fetchData() {
  try {
    const response = await fetch('https://api.example.com/data');

    // Check for HTTP error status
    if (!response.ok) {
      throw new Error(`HTTP error! Status: ${response.status}`);
    }

    const data = await response.json();
    console.log(data);
  } catch (error) {
    // Handle specific error types
    if (error.code === 'ECONNREFUSED') {
      console.error('Connection refused! Server might be down.');
    } else if (error.code === 'ETIMEDOUT') {
      console.error('Request timed out! Server might be overloaded.');
    } else if (error.code.startsWith('EHOST')) {
      console.error('Network unreachable! Check your internet connection.');
    } else {
      console.error('General error:', error);
    }
  }
}

fetchData();

Explanation:

1. response.ok: The response.ok property checks if the HTTP response status code is in the range of 200-299 (success). If not, it throws a custom error indicating the HTTP status.
2. error.code: If the fetch throws an error, we check the error.code property. It provides valuable information about the specific network error, allowing you to handle it accordingly.

Best Practices for Robust Error Handling

• Retry Mechanisms: Implement retry logic for transient errors like connection refused or timeouts.
• Backoff Strategies: Introduce exponential backoff to avoid overwhelming the server during repeated retries.
• Error Logging: Log all network errors for debugging and monitoring.
• User Feedback: Provide clear and helpful messages to the user based on the detected error type.

Conclusion

By understanding the nuances of network error types and implementing appropriate error handling strategies, you can build Node.js applications that are resilient, informative, and user-friendly.

Remember, this solution is a foundation for further customization based on your specific needs. Explore additional error handling techniques and integrate them seamlessly into your Node.js applications.