httpbin-like client to test CDN caching and stale-while-revalidate

client.py

#!/usr/bin/env python3

import sys
import time
import urllib.request
from threading import Thread


class fgcolor:
    green = "\x1b[32;20m"
    yellow = "\x1b[33;20m"
    red = "\x1b[31;20m"
    reset = "\x1b[0m"

class IgnoreErrors(urllib.request.HTTPErrorProcessor):
    def http_response(self, request, response):
        return response
    https_response = http_response

def fetch(url):
    t_start = time.time()
    opener = urllib.request.build_opener(IgnoreErrors)
    req = urllib.request.Request(url)
    with opener.open(req) as response:
        ttfb = time.time() - t_start
        ttfb_color = fgcolor.green if ttfb < 0.5 else fgcolor.red

        status = response.status
        status_color = fgcolor.green if 200 <= status < 300 else fgcolor.red

        # Extract some headers.
        age = response.getheader("age", "")
        x_cache = response.getheader("x-cache", "")

        # Extract some info from the body.
        body = response.read()
        body_len = len(body)
        generated_by = "origin"
        if b"Generated by cloudfront" in body:
            generated_by = "CloudFront"
        generated_by_color = fgcolor.green if generated_by == "origin" else fgcolor.red

        print(
            f"ttfb={ttfb_color}{ttfb:5.3f}{fgcolor.reset}"
            f" status={status_color}{status}{fgcolor.reset}"
            f" age={age}"
            f" bytes={body_len}"
            f" generated_by={generated_by_color}{generated_by}{fgcolor.reset}"
            f" x-cache={x_cache}"
        )


url = "https://FIXME.cloudfront.net/?wait_ms=2500&header=cache-control=max-age=10,stale-while-revalidate=27&status_code_after_ms=9000&status_code_after=502&session_ttl_ms=300000&session_id=test001"
if len(sys.argv) > 1:
    url = sys.argv[1]

while True:
    Thread(target=fetch, args=[url]).start()
    time.sleep(0.1)