Handling API Errors Explained

Key Concepts

• Error Handling in APIs
• HTTP Status Codes
• Custom Error Responses
• Logging Errors
• Exception Handling
• Testing Error Scenarios
• Graceful Degradation

Error Handling in APIs

Error handling in APIs is crucial for providing meaningful feedback to clients when something goes wrong. Proper error handling ensures that clients can understand what happened and take appropriate action.

HTTP Status Codes

HTTP status codes are three-digit numbers that indicate the outcome of an HTTP request. Common status codes include 200 (OK), 400 (Bad Request), 404 (Not Found), and 500 (Internal Server Error). These codes help clients understand the nature of the error.

from flask import Flask, jsonify

app = Flask(__name__)

@app.route('/resource/')
def get_resource(id):
    if id < 0:
        return jsonify({"error": "Invalid ID"}), 400
    return jsonify({"id": id, "data": "Some data"}), 200
    

Custom Error Responses

Custom error responses allow you to provide more detailed information about the error. This can include error messages, error codes, and suggestions for resolving the issue. Custom responses make the API more user-friendly.

@app.errorhandler(404)
def not_found(error):
    return jsonify({"error": "Resource not found", "code": 404}), 404

@app.errorhandler(500)
def internal_error(error):
    return jsonify({"error": "Internal server error", "code": 500}), 500
    

Logging Errors

Logging errors helps in diagnosing and fixing issues. By logging errors, you can track what went wrong, when it happened, and under what conditions. This is essential for maintaining and improving the API.

import logging

logging.basicConfig(level=logging.ERROR)

@app.route('/log_error')
def log_error():
    try:
        # Some code that might raise an error
        raise ValueError("An error occurred")
    except ValueError as e:
        logging.error(f"Error: {str(e)}")
        return jsonify({"error": "An error occurred"}), 500
    

Exception Handling

Exception handling involves catching and managing exceptions that occur during the execution of the API. This prevents the API from crashing and ensures that errors are handled gracefully.

@app.route('/divide//')
def divide(a, b):
    try:
        result = a / b
    except ZeroDivisionError:
        return jsonify({"error": "Division by zero"}), 400
    return jsonify({"result": result}), 200
    

Testing Error Scenarios

Testing error scenarios ensures that your API handles errors correctly. By simulating various error conditions, you can verify that the API responds appropriately and that error messages are clear and helpful.

def test_divide_by_zero():
    response = app.test_client().get('/divide/10/0')
    assert response.status_code == 400
    assert response.json == {"error": "Division by zero"}
    

Graceful Degradation

Graceful degradation involves designing the API to continue functioning, albeit with reduced capabilities, when errors occur. This ensures that the API remains usable even when parts of it fail.

@app.route('/degrade')
def degrade():
    try:
        # Some critical operation
        raise Exception("Critical error")
    except Exception:
        return jsonify({"warning": "Service degraded", "data": "Partial data"}), 206