scientific-programming-exercises/exam/ex01/proxy.py

"""
Module to fetch new proxies from 
https://www.proxynova.com/proxy-server-list/country-de/
"""

import requests
import logging
import time
from bs4 import BeautifulSoup

from cfg import config

logger = logging.getLogger(__name__)

class NoMoreProxiesException(Exception): 
	pass

def get_data_with_proxy(url, conn_object, visit_first=None):
	cursor = conn_object.cursor()
	# Assume that table name is proxies
	cursor.execute('''SELECT proxy, lasttime_could_not_be_used FROM proxies ORDER BY lasttime_could_not_be_used ASC''')
	headers = {}
	for i, lasttime_could_not_be_used in cursor:
		session = requests.Session()
		session.proxies = { 'http': i}
		try:
			response = session.get(url, headers=headers, timeout=3)
		except Exception as e:
			if(isinstance(e, KeyboardInterrupt)):
				raise e
		# If proxy is invalid/inactive, update lasttime could not be used and go next proxy
			cursor.execute('''UPDATE proxies SET lasttime_could_not_be_used = %s WHERE proxy = %s ''',
					 (time.time(), i))
			continue
		# If text is empty, update lasttime could not be used and go next proxy
		if not response.text or 399 < response.status_code < 600:
			cursor.execute('''UPDATE proxies SET lasttime_could_not_be_used = %s WHERE proxy = %s ''',
					 (time.time(), i))
			continue
		# Be nice to Wikipedia.
		time.sleep(0.1)
		return response.json()
	raise NoMoreProxiesException("No more proxies left")


def fetch_proxies(connection):
	"""
	Fetch new proxies from https://us-proxy.org/ and put them
	in the database ``connection``.
	"""
	resp = requests.request(url="https://www.proxynova.com/proxy-server-list/country-de/", method="GET")
	logger.info("request status code: {}; elapsed us: {}".format(resp.status_code,
				resp.elapsed.microseconds))
	if(resp.status_code != 200):
		logger.error("status code is not 200")
		raise Exception("failed to retrieve proxy list")
	soup = BeautifulSoup(resp.text, "html.parser")

	cursor = connection.cursor()
	cnt = 0
	for ip_addr, port in _get_rows(soup):

		url = "http://{}:{}".format(ip_addr, port)

		if(not proxy_is_in_db(url, connection)):
			cursor.execute("INSERT INTO proxies VALUES(%s, 0)", (url,))
			cnt += 1
	logging.info("added {} new proxies".format(cnt))
	connection.commit()


		

def _get_rows(soup):
	for i, row in enumerate(soup.findAll("tr")):
		# first row is a header
		if(i == 0):
			continue
		try:
			columns = row.findAll("td")
			ip_addr, port = [i.get_text() for i in columns[0:2]]
			port = port.strip()
			# Well they thought that they kinda obfuscated that.
			# Unfortunately their obfuscation is crap and so this bypasses
			# it.
			ip_addr = ip_addr[25:30] + ip_addr[45:-5]
			yield ip_addr, port
		except Exception as e:
			continue
	logger.info("retrieved {} proxies".format(i))
			
		
def proxy_is_in_db(url, connection):
	cursor = connection.cursor()
	cursor.execute("SELECT proxy FROM proxies WHERE proxy = %s", (url,))
	return bool(cursor.fetchall())