76 lines
2.3 KiB
Python
76 lines
2.3 KiB
Python
# -*- coding: utf-8 -*-
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# Copyright (C) 2019 Tobias Gruetzmacher
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from __future__ import absolute_import, division, print_function
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from collections import defaultdict
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from random import uniform
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from time import time, sleep
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import requests
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from requests.adapters import HTTPAdapter
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from requests.packages.urllib3.util.retry import Retry
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from six.moves.urllib.parse import urlparse
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from .configuration import UserAgent
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# Default number of retries
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MaxRetries = 3
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# Factor for retry backoff (see urllib3.util.retry, this default means
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# 2s, 4s, 8s)
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RetryBackoffFactor = 2
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# Default connection timeout
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ConnectionTimeoutSecs = 60
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class Session(requests.Session):
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"""This session implements a very simple host-based throttling system: For
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each hostname we see, we keep a record on when is the earliest time we want
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to send the next request: If before sending a request this time isn't
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reached, we sleep a bit until the requirements are satisfied. By default,
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we only delay a random amount of at most 0.3sec - but some hosts might need
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longer delays.
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"""
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def __init__(self):
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super(Session, self).__init__()
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retry = Retry(MaxRetries, backoff_factor=RetryBackoffFactor)
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self.mount('http://', HTTPAdapter(max_retries=retry))
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self.mount('https://', HTTPAdapter(max_retries=retry))
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self.headers.update({'User-Agent': UserAgent})
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self.throttles = defaultdict(lambda: RandomThrottle(0.0, 0.3))
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def send(self, request, **kwargs):
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if 'timeout' not in kwargs:
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kwargs['timeout'] = ConnectionTimeoutSecs
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hostname = urlparse(request.url).hostname
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self.throttles[hostname].delay()
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return super(Session, self).send(request, **kwargs)
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def add_throttle(self, hostname, th_min, th_max):
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"""Adds a new throttle for a host: Might overwrite the existing one.
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"""
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self.throttles[hostname] = RandomThrottle(th_min, th_max)
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class RandomThrottle(object):
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def __init__(self, th_min, th_max):
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self.th_min = th_min
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self.th_max = th_max
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self.next = time()
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def delay(self):
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d = self.next - time()
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if d > 0:
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sleep(d)
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self.next = time() + uniform(self.th_min, self.th_max)
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# A default session for cookie and connection sharing
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default_session = Session()
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