Implementing Retry Mechanism in Python urllib3 for Resilient HTTP Requests

Last update on February 08 2024 05:28:33 (UTC/GMT +8 hours)

Python urllib3 : Exercise-16 with Solution

Write a Python program that sets up a retry mechanism for failed requests with urllib3.Retry class.

Sample Solution:

Python Code :

# Import necessary libraries
import urllib3
from urllib3.util.retry import Retry
from urllib3.exceptions import MaxRetryError

# Function to make a request with retry mechanism
def make_request_with_retry(url):
    try:
        # Configure the Retry class with desired parameters
        retries = Retry(
            total=3,  # Total number of allowed retries
            backoff_factor=0.5,  # Factor by which retry delays increase
            status_forcelist=[500, 502, 503, 504],  # HTTP status codes to retry
        )

        # Create a PoolManager with the configured Retry class
        http = urllib3.PoolManager(retries=retries)

        # Make a GET request with retry mechanism
        response = http.request('GET', url)

        # Check if the request was successful (status code 200)
        if response.status == 200:
            print("Request Successful:")
            print(response.data.decode('utf-8'))
        else:
            print(f"Error: Unable to fetch data. Status Code: {response.status}")

    except MaxRetryError as e:
        print(f"Error: Maximum retries exceeded. {e}")

# Define the URL for the request
url = 'https://www.example.com'  # Replace with the actual URL

# Make the request with retry mechanism
make_request_with_retry(url)

Sample Output:

Request Successful:
<!doctype html<
<html<
<head<
    <title<Example Domain</title<

    <meta charset="utf-8" /<
    <meta http-equiv="Content-type" content="text/html; charset=utf-8" /<
    <meta name="viewport" content="width=device-width, initial-scale=1" /<
    <style type="text/css"<
    body {
        background-color: #f0f0f2;
        margin: 0;
        padding: 0;
        font-family: -apple-system, system-ui, BlinkMacSystemFont, "Segoe UI", "Open Sans", "Helvetica Neue", Helvetica, Arial, sans-serif;
        
    }
    div {
        width: 600px;
        margin: 5em auto;
        padding: 2em;
        background-color: #fdfdff;
        border-radius: 0.5em;
        box-shadow: 2px 3px 7px 2px rgba(0,0,0,0.02);
    }
    a:link, a:visited {
        color: #38488f;
        text-decoration: none;
    }
    @media (max-width: 700px) {
        div {
            margin: 0 auto;
            width: auto;
        }
    }
    </style<    
</head<

<body<
<div<
    <h1<Example Domain</h1<
    <p<This domain is for use in illustrative examples in documents. You may use this
    domain in literature without prior coordination or asking for permission.</p<
    <p<<a href="https://www.iana.org/domains/example"<More information...</a<</p<
</div<
</body<
</html<


runfile('C:/Users/ME/untitled30.py', wdir='C:/Users/ME')
Request Successful:
<!doctype html<
<html<
<head<
    <title<Example Domain</title<

    <meta charset="utf-8" /<
    <meta http-equiv="Content-type" content="text/html; charset=utf-8" /<
    <meta name="viewport" content="width=device-width, initial-scale=1" /<
    <style type="text/css"<
    body {
        background-color: #f0f0f2;
        margin: 0;
        padding: 0;
        font-family: -apple-system, system-ui, BlinkMacSystemFont, "Segoe UI", "Open Sans", "Helvetica Neue", Helvetica, Arial, sans-serif;
        
    }
    div {
        width: 600px;
        margin: 5em auto;
        padding: 2em;
        background-color: #fdfdff;
        border-radius: 0.5em;
        box-shadow: 2px 3px 7px 2px rgba(0,0,0,0.02);
    }
    a:link, a:visited {
        color: #38488f;
        text-decoration: none;
    }
    @media (max-width: 700px) {
        div {
            margin: 0 auto;
            width: auto;
        }
    }
    </style<    
</head<

<body<
<div<
    <h1<Example Domain</h1<
    <p<This domain is for use in illustrative examples in documents. You may use this
    domain in literature without prior coordination or asking for permission.</p<
    <p<<a href="https://www.iana.org/domains/example"<More information...</a<</p<
</div<
</body<
</html<

Explanation:

Here's a brief explanation of the above Python urllib3 library code:

Import Libraries: Import the necessary libraries, including "urllib3" for making HTTP requests.
Define Function: Create a function "make_request_with_retry()" that takes a URL as a parameter and makes a request with a retry mechanism.
Configure Retry Class: Create a "Retry" class instance with parameters like 'total' (total number of retries), 'backoff_factor' (factor by which retry delays increase), and 'status_forcelist' (HTTP status codes to retry).
Create PoolManager: Create an instance of "urllib3.PoolManager" with the configured 'Retry' class.
Make Request with Retry: Use the "http.request" method to make a GET request with the retry mechanism.
Handle Response: Check if the request was successful (status code 200) and print the response. Otherwise, print an error message.
Exception Handling: Catch and handle 'MaxRetryError' exceptions that might occur when the maximum number of retries is exceeded.
Make Request with Retry: Call the "make_request_with_retry()" function to initiate the request with the configured retry mechanism.

Flowchart:

Python Code Editor :

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