Setting Scrapy proxy middleware to rotate on each request

Question

This question necessarily comes in two forms, because I don't know the better route to a solution.

A site I'm crawling kicks me to a redirected "User Blocked" page often, but the frequency (by requests/time) seems random, and they appear to have a blacklist blocking many of the "open" proxies list I'm using through Proxymesh. So...

1. When Scrapy receives a "Redirect" to its request (e.g. DEBUG: Redirecting (302) to (GET http://.../you_got_blocked.aspx) from (GET http://.../page-544.htm)), does it continue to try to get to page-544.htm, or will it continue on to page-545.htm and forever lose out on page-544.htm? If it "forgets" (or counts it as visited), is there a way to tell it to keep retrying that page? (If it does that naturally, then yay, and good to know...)

2. What is the most efficient solution?

(a) What I'm currently doing: using a proxymesh rotating Proxy through the http_proxy environment variable, which appears to rotate proxies often enough to at least fairly regularly get through the target site's redirections. (Downsides: the open proxies are slow to ping, there are only so many of them, proxymesh will eventually start charging me per gig past 10 gigs, I only need them to rotate when redirected, I don't know how often or on what trigger they rotate, and the above: I don't know if the pages I'm being redirected from are being re-queued by Scrapy...) (If Proxymesh is rotating on each request, then I'm okay with paying reasonable costs.)

(b) Would it make sense (and be simple) to use middleware to reselect a new proxy on each redirection? What about on every single request? Would that make more sense through something else like TOR or Proxifier? If this is relatively straightforward, how would I set it up? I've read something like this in a few places, but most are outdated with broken links or deprecated Scrapy commands.

For reference, I do have middleware currently set up for Proxy Mesh (yes, I'm using the http_proxy environment variable, but I'm a fan of redundancy when it comes to not getting in trouble). So this is what I have for that currently, in case that matters:

 class ProxyMiddleware(object):
  def process_request(self, request, spider):
    request.meta['proxy'] = "http://open.proxymesh.com:[port number]"

    proxy_user_pass = "username:password"
    encoded_user_pass = base64.encodestring(proxy_user_pass)
    request.headers['Proxy-Authorization'] = 'Basic ' + encoded_user_pass

Solution

yesterday I had similar task with proxy and protection against DDoS. ( I've parsed a site ) The idea is in random.choice. Every request has a chance of changing IP. Scrapy uses Tor and telnetlib3. You need to configure ControlPort password.

from scrapy import log
from settings import USER_AGENT_LIST

import random
import telnetlib
import time


# 15% ip change
class RetryChangeProxyMiddleware(object):
    def process_request(self, request, spider):
        if random.choice(xrange(1,100)) <= 15:
            log.msg('Changing proxy')
            tn = telnetlib.Telnet('127.0.0.1', 9051)
            tn.read_until("Escape character is '^]'.", 2)
            tn.write('AUTHENTICATE "<PASSWORD HERE>"\r\n')
            tn.read_until("250 OK", 2)
            tn.write("signal NEWNYM\r\n")
            tn.read_until("250 OK", 2)
            tn.write("quit\r\n")
            tn.close()
            log.msg('>>>> Proxy changed. Sleep Time')
            time.sleep(10)



# 30% useragent change
class RandomUserAgentMiddleware(object):
    def process_request(self, request, spider):
        if random.choice(xrange(1,100)) <= 30:
            log.msg('Changing UserAgent')
            ua  = random.choice(USER_AGENT_LIST)
            if ua:
                request.headers.setdefault('User-Agent', ua)
            log.msg('>>>> UserAgent changed')