Scrapy学习-23-分布式爬虫

scrapy-redis分布式爬虫

分布式需要解决的问题

　　request队列集中管理

　　去重集中管理

　　存储管理

 

使用scrapy-redis实现分布式爬虫

　　github开源项目： https://github.com/rmax/scrapy-redis

 

相关依赖模块下载

pip isntall redis

pip install scrapy

使用

配置settings

SCHEDULER = "scrapy_redis.scheduler.Scheduler"

DUPEFILTER_CLASS = "scrapy_redis.dupefilter.RFPDupeFilter"

ITEM_PIPELINES = {
    'scrapy_redis.pipelines.RedisPipeline': 300
}

在spider文件中创建一个spider项目的python文件

# 基于basic_spider

from scrapy_redis.spiders import RedisSpider

class MySpider(RedisSpider):
    """Spider that reads urls from redis queue (myspider:start_urls)."""
    name = 'myspider_redis'
    redis_key = 'myspider:start_urls'

    def __init__(self, *args, **kwargs):
        # Dynamically define the allowed domains list.
        domain = kwargs.pop('domain', '')
        self.allowed_domains = filter(None, domain.split(','))
        super(MySpider, self).__init__(*args, **kwargs)

    def parse(self, response):
        return {
            'name': response.css('title::text').extract_first(),
            'url': response.url,
        }

# 基于crawl_spider

from scrapy.spiders import Rule
from scrapy.linkextractors import LinkExtractor

from scrapy_redis.spiders import RedisCrawlSpider

class MyCrawler(RedisCrawlSpider):
    """Spider that reads urls from redis queue (myspider:start_urls)."""
    name = 'mycrawler_redis'
    redis_key = 'mycrawler:start_urls'

    rules = (
        # follow all links
        Rule(LinkExtractor(), callback='parse_page', follow=True),
    )

    def __init__(self, *args, **kwargs):
        # Dynamically define the allowed domains list.
        domain = kwargs.pop('domain', '')
        self.allowed_domains = filter(None, domain.split(','))
        super(MyCrawler, self).__init__(*args, **kwargs)

    def parse_page(self, response):
        return {
            'name': response.css('title::text').extract_first(),
            'url': response.url,
        }

运行分布式爬虫

scrapy runspider myspider.py

初始化redis字段

redis-cli lpush myspider:start_urls http://google.com

# scrapy-redis会从这个myspider:start_urls获取第一个爬取的URL

redis中默认生成的字段

myspider:requests

myspider:dupefilter

运行

　　使用scrapy创建main文件的方式运行即可

 

 

scrapy-redis源码

connection.py、defaults.py

　　处理redis对象

 

dupefilter.py

# scrapy-redis中的dupefilter 与scrapy中的dupefilters，基于于同一个类，实现的接口都相同

import logging
import time

from scrapy.dupefilters import BaseDupeFilter
from scrapy.utils.request import request_fingerprint

from . import defaults
from .connection import get_redis_from_settings

logger = logging.getLogger(__name__)

# TODO: Rename class to RedisDupeFilter.
class RFPDupeFilter(BaseDupeFilter):
    """Redis-based request duplicates filter.

    This class can also be used with default Scrapy's scheduler.

    """

    logger = logger

    def __init__(self, server, key, debug=False):
        """Initialize the duplicates filter.

        Parameters
        ----------
        server : redis.StrictRedis
            The redis server instance.
        key : str
            Redis key Where to store fingerprints.
        debug : bool, optional
            Whether to log filtered requests.

        """
        self.server = server  # 在connection.py中被实例化了,是一个redis对象
        self.key = key
        self.debug = debug
        self.logdupes = True

    @classmethod
    def from_settings(cls, settings):
        """Returns an instance from given settings.

        This uses by default the key ``dupefilter:<timestamp>``. When using the
        ``scrapy_redis.scheduler.Scheduler`` class, this method is not used as
        it needs to pass the spider name in the key.

        Parameters
        ----------
        settings : scrapy.settings.Settings

        Returns
        -------
        RFPDupeFilter
            A RFPDupeFilter instance.

        """
        server = get_redis_from_settings(settings)
        # XXX: This creates one-time key. needed to support to use this
        # class as standalone dupefilter with scrapy's default scheduler
        # if scrapy passes spider on open() method this wouldn't be needed
        # TODO: Use SCRAPY_JOB env as default and fallback to timestamp.
        key = defaults.DUPEFILTER_KEY % {'timestamp': int(time.time())}
        debug = settings.getbool('DUPEFILTER_DEBUG')
        return cls(server, key=key, debug=debug)

    @classmethod
    def from_crawler(cls, crawler):
        """Returns instance from crawler.

        Parameters
        ----------
        crawler : scrapy.crawler.Crawler

        Returns
        -------
        RFPDupeFilter
            Instance of RFPDupeFilter.

        """
        return cls.from_settings(crawler.settings)

    def request_seen(self, request):
        """Returns True if request was already seen.

        Parameters
        ----------
        request : scrapy.http.Request

        Returns
        -------
        bool

        """
        fp = self.request_fingerprint(request)
        # This returns the number of values added, zero if already exists.
        added = self.server.sadd(self.key, fp)
        return added == 0

    def request_fingerprint(self, request):
        """Returns a fingerprint for a given request.

        Parameters
        ----------
        request : scrapy.http.Request

        Returns
        -------
        str

        """
        return request_fingerprint(request)

    @classmethod
    def from_spider(cls, spider):
        settings = spider.settings
        server = get_redis_from_settings(settings)
        dupefilter_key = settings.get("SCHEDULER_DUPEFILTER_KEY", defaults.SCHEDULER_DUPEFILTER_KEY)
        key = dupefilter_key % {'spider': spider.name}
        debug = settings.getbool('DUPEFILTER_DEBUG')
        return cls(server, key=key, debug=debug)

    def close(self, reason=''):
        """Delete data on close. Called by Scrapy's scheduler.

        Parameters
        ----------
        reason : str, optional

        """
        self.clear()

    def clear(self):
        """Clears fingerprints data."""
        self.server.delete(self.key)

    def log(self, request, spider):
        """Logs given request.

        Parameters
        ----------
        request : scrapy.http.Request
        spider : scrapy.spiders.Spider

        """
        if self.debug:
            msg = "Filtered duplicate request: %(request)s"
            self.logger.debug(msg, {'request': request}, extra={'spider': spider})
        elif self.logdupes:
            msg = ("Filtered duplicate request %(request)s"
                " - no more duplicates will be shown"
                " (see DUPEFILTER_DEBUG to show all duplicates)")
            self.logger.debug(msg, {'request': request}, extra={'spider': spider})
            self.logdupes = False

picklecompat.py

# 这里使用的就是python的pickle模块，一个兼容py2和py3的串行化工具。这个serializer主要用于一会的scheduler存reuqest对象

"""A pickle wrapper module with protocol=-1 by default."""

try:
    import cPickle as pickle  # PY2
except ImportError:
    import pickle

def loads(s):
    return pickle.loads(s)

def dumps(obj):
    return pickle.dumps(obj, protocol=-1)

pipelines.py

# 用于将items序列化后异步（deferToThread）存放到reids中

# 此处pipelines不是必须使用的，我们可以自己写一个pipelines将数据保存在本地

from scrapy.utils.misc import load_object
from scrapy.utils.serialize import ScrapyJSONEncoder
from twisted.internet.threads import deferToThread

from . import connection, defaults

default_serialize = ScrapyJSONEncoder().encode

class RedisPipeline(object):
    """Pushes serialized item into a redis list/queue

    Settings
    --------
    REDIS_ITEMS_KEY : str
        Redis key where to store items.
    REDIS_ITEMS_SERIALIZER : str
        Object path to serializer function.

    """

    def __init__(self, server,
                key=defaults.PIPELINE_KEY,
                serialize_func=default_serialize):
        """Initialize pipeline.

        Parameters
        ----------
        server : StrictRedis
            Redis client instance.
        key : str
            Redis key where to store items.
        serialize_func : callable
            Items serializer function.

        """
        self.server = server
        self.key = key
        self.serialize = serialize_func

    @classmethod
    def from_settings(cls, settings):
        params = {
            'server': connection.from_settings(settings),
        }
        if settings.get('REDIS_ITEMS_KEY'):
            params['key'] = settings['REDIS_ITEMS_KEY']
        if settings.get('REDIS_ITEMS_SERIALIZER'):
            params['serialize_func'] = load_object(
                settings['REDIS_ITEMS_SERIALIZER']
            )

        return cls(**params)

    @classmethod
    def from_crawler(cls, crawler):
        return cls.from_settings(crawler.settings)

    def process_item(self, item, spider):
        return deferToThread(self._process_item, item, spider)

    def _process_item(self, item, spider):
        key = self.item_key(item, spider)
        data = self.serialize(item)
        self.server.rpush(key, data)
        return item

    def item_key(self, item, spider):
        """Returns redis key based on given spider.

        Override this function to use a different key depending on the item
        and/or spider.

        """
        return self.key % {'spider': spider.name}

queue.py

# 此处定义了三种队列先进先出队列、优先级队列、后进先出队列

from scrapy.utils.reqser import request_to_dict, request_from_dict

from . import picklecompat

class Base(object):
    """Per-spider base queue class"""

    def __init__(self, server, spider, key, serializer=None):
        """Initialize per-spider redis queue.

        Parameters
        ----------
        server : StrictRedis
            Redis client instance.
        spider : Spider
            Scrapy spider instance.
        key: str
            Redis key where to put and get messages.
        serializer : object
            Serializer object with ``loads`` and ``dumps`` methods.

        """
        if serializer is None:
            # Backward compatibility.
            # TODO: deprecate pickle.
            serializer = picklecompat
        if not hasattr(serializer, 'loads'):
            raise TypeError("serializer does not implement 'loads' function: %r"
                            % serializer)
        if not hasattr(serializer, 'dumps'):
            raise TypeError("serializer '%s' does not implement 'dumps' function: %r"
                            % serializer)

        self.server = server
        self.spider = spider
        self.key = key % {'spider': spider.name}
        self.serializer = serializer

    def _encode_request(self, request):
        """Encode a request object"""
        obj = request_to_dict(request, self.spider)
        return self.serializer.dumps(obj)

    def _decode_request(self, encoded_request):
        """Decode an request previously encoded"""
        obj = self.serializer.loads(encoded_request)
        return request_from_dict(obj, self.spider)

    def __len__(self):
        """Return the length of the queue"""
        raise NotImplementedError

    def push(self, request):
        """Push a request"""
        raise NotImplementedError

    def pop(self, timeout=0):
        """Pop a request"""
        raise NotImplementedError

    def clear(self):
        """Clear queue/stack"""
        self.server.delete(self.key)

class FifoQueue(Base):
    """Per-spider FIFO queue"""

    def __len__(self):
        """Return the length of the queue"""
        return self.server.llen(self.key)

    def push(self, request):
        """Push a request"""
        self.server.lpush(self.key, self._encode_request(request))

    def pop(self, timeout=0):
        """Pop a request"""
        if timeout > 0:
            data = self.server.brpop(self.key, timeout)
            if isinstance(data, tuple):
                data = data[1]
        else:
            data = self.server.rpop(self.key)
        if data:
            return self._decode_request(data)

class PriorityQueue(Base):
    """Per-spider priority queue abstraction using redis' sorted set"""

    def __len__(self):
        """Return the length of the queue"""
        return self.server.zcard(self.key)

    def push(self, request):
        """Push a request"""
        data = self._encode_request(request)
        score = -request.priority
        # We don't use zadd method as the order of arguments change depending on
        # whether the class is Redis or StrictRedis, and the option of using
        # kwargs only accepts strings, not bytes.
        self.server.execute_command('ZADD', self.key, score, data)

    def pop(self, timeout=0):
        """
        Pop a request
        timeout not support in this queue class
        """
        # use atomic range/remove using multi/exec
        pipe = self.server.pipeline()
        pipe.multi()
        pipe.zrange(self.key, 0, 0).zremrangebyrank(self.key, 0, 0)
        results, count = pipe.execute()
        if results:
            return self._decode_request(results[0])

class LifoQueue(Base):
    """Per-spider LIFO queue."""

    def __len__(self):
        """Return the length of the stack"""
        return self.server.llen(self.key)

    def push(self, request):
        """Push a request"""
        self.server.lpush(self.key, self._encode_request(request))

    def pop(self, timeout=0):
        """Pop a request"""
        if timeout > 0:
            data = self.server.blpop(self.key, timeout)
            if isinstance(data, tuple):
                data = data[1]
        else:
            data = self.server.lpop(self.key)

        if data:
            return self._decode_request(data)

# TODO: Deprecate the use of these names.
SpiderQueue = FifoQueue
SpiderStack = LifoQueue
SpiderPriorityQueue = PriorityQueue

scheduler.py

# 主要的两个函数enqueue_request、next_request

import importlib
import six

from scrapy.utils.misc import load_object

from . import connection, defaults

# TODO: add SCRAPY_JOB support.
class Scheduler(object):
    """Redis-based scheduler

    Settings
    --------
    SCHEDULER_PERSIST : bool (default: False)
        Whether to persist or clear redis queue.
    SCHEDULER_FLUSH_ON_START : bool (default: False)
        Whether to flush redis queue on start.
    SCHEDULER_IDLE_BEFORE_CLOSE : int (default: 0)
        How many seconds to wait before closing if no message is received.
    SCHEDULER_QUEUE_KEY : str
        Scheduler redis key.
    SCHEDULER_QUEUE_CLASS : str
        Scheduler queue class.
    SCHEDULER_DUPEFILTER_KEY : str
        Scheduler dupefilter redis key.
    SCHEDULER_DUPEFILTER_CLASS : str
        Scheduler dupefilter class.
    SCHEDULER_SERIALIZER : str
        Scheduler serializer.

    """

    def __init__(self, server,
                persist=False,
                flush_on_start=False,
                queue_key=defaults.SCHEDULER_QUEUE_KEY,
                queue_cls=defaults.SCHEDULER_QUEUE_CLASS,
                dupefilter_key=defaults.SCHEDULER_DUPEFILTER_KEY,
                dupefilter_cls=defaults.SCHEDULER_DUPEFILTER_CLASS,
                idle_before_close=0,
                serializer=None):
        """Initialize scheduler.

        Parameters
        ----------
        server : Redis
            The redis server instance.
        persist : bool
            Whether to flush requests when closing. Default is False.
        flush_on_start : bool
            Whether to flush requests on start. Default is False.
        queue_key : str
            Requests queue key.
        queue_cls : str
            Importable path to the queue class.
        dupefilter_key : str
            Duplicates filter key.
        dupefilter_cls : str
            Importable path to the dupefilter class.
        idle_before_close : int
            Timeout before giving up.

        """
        if idle_before_close < 0:
            raise TypeError("idle_before_close cannot be negative")

        self.server = server
        self.persist = persist
        self.flush_on_start = flush_on_start
        self.queue_key = queue_key
        self.queue_cls = queue_cls
        self.dupefilter_cls = dupefilter_cls
        self.dupefilter_key = dupefilter_key
        self.idle_before_close = idle_before_close
        self.serializer = serializer
        self.stats = None

    def __len__(self):
        return len(self.queue)

    @classmethod
    def from_settings(cls, settings):
        kwargs = {
            'persist': settings.getbool('SCHEDULER_PERSIST'),
            'flush_on_start': settings.getbool('SCHEDULER_FLUSH_ON_START'),
            'idle_before_close': settings.getint('SCHEDULER_IDLE_BEFORE_CLOSE'),
        }

        # If these values are missing, it means we want to use the defaults.
        optional = {
            # TODO: Use custom prefixes for this settings to note that are
            # specific to scrapy-redis.
            'queue_key': 'SCHEDULER_QUEUE_KEY',
            'queue_cls': 'SCHEDULER_QUEUE_CLASS',
            'dupefilter_key': 'SCHEDULER_DUPEFILTER_KEY',
            # We use the default setting name to keep compatibility.
            'dupefilter_cls': 'DUPEFILTER_CLASS',
            'serializer': 'SCHEDULER_SERIALIZER',
        }
        for name, setting_name in optional.items():
            val = settings.get(setting_name)
            if val:
                kwargs[name] = val

        # Support serializer as a path to a module.
        if isinstance(kwargs.get('serializer'), six.string_types):
            kwargs['serializer'] = importlib.import_module(kwargs['serializer'])

        server = connection.from_settings(settings)
        # Ensure the connection is working.
        server.ping()

        return cls(server=server, **kwargs)

    @classmethod
    def from_crawler(cls, crawler):
        instance = cls.from_settings(crawler.settings)
        # FIXME: for now, stats are only supported from this constructor
        instance.stats = crawler.stats
        return instance

    def open(self, spider):
        self.spider = spider

        try:
            self.queue = load_object(self.queue_cls)(
                server=self.server,
                spider=spider,
                key=self.queue_key % {'spider': spider.name},
                serializer=self.serializer,
            )
        except TypeError as e:
            raise ValueError("Failed to instantiate queue class '%s': %s",
                            self.queue_cls, e)

        self.df = load_object(self.dupefilter_cls).from_spider(spider)

        if self.flush_on_start:
            self.flush()
        # notice if there are requests already in the queue to resume the crawl
        if len(self.queue):
            spider.log("Resuming crawl (%d requests scheduled)" % len(self.queue))

    def close(self, reason):
        if not self.persist:
            self.flush()

    def flush(self):
        self.df.clear()
        self.queue.clear()

    def enqueue_request(self, request):
        if not request.dont_filter and self.df.request_seen(request):
            self.df.log(request, self.spider)
            return False
        if self.stats:
            self.stats.inc_value('scheduler/enqueued/redis', spider=self.spider)
        self.queue.push(request)
        return True

    def next_request(self):
        block_pop_timeout = self.idle_before_close
        request = self.queue.pop(block_pop_timeout)
        if request and self.stats:
            self.stats.inc_value('scheduler/dequeued/redis', spider=self.spider)
        return request

    def has_pending_requests(self):
        return len(self) > 0

utils.py

# 兼容python2和python3

import six

def bytes_to_str(s, encoding='utf-8'):
    """Returns a str if a bytes object is given."""
    if six.PY3 and isinstance(s, bytes):
        return s.decode(encoding)
    return s

spiders.py

# 继承了RedisMixin和Spider

# RedisMixin重载了start_request(),使用自己编写的函数next_requests，实现从redis中获取数据

from scrapy import signals
from scrapy.exceptions import DontCloseSpider
from scrapy.spiders import Spider, CrawlSpider

from . import connection, defaults
from .utils import bytes_to_str

class RedisMixin(object):
    """Mixin class to implement reading urls from a redis queue."""
    redis_key = None
    redis_batch_size = None
    redis_encoding = None

    # Redis client placeholder.
    server = None

    def start_requests(self):
        """Returns a batch of start requests from redis."""
        return self.next_requests()

    def setup_redis(self, crawler=None):
        """Setup redis connection and idle signal.

        This should be called after the spider has set its crawler object.
        """
        if self.server is not None:
            return

        if crawler is None:
            # We allow optional crawler argument to keep backwards
            # compatibility.
            # XXX: Raise a deprecation warning.
            crawler = getattr(self, 'crawler', None)

        if crawler is None:
            raise ValueError("crawler is required")

        settings = crawler.settings

        if self.redis_key is None:
            self.redis_key = settings.get(
                'REDIS_START_URLS_KEY', defaults.START_URLS_KEY,
            )

        self.redis_key = self.redis_key % {'name': self.name}

        if not self.redis_key.strip():
            raise ValueError("redis_key must not be empty")

        if self.redis_batch_size is None:
            # TODO: Deprecate this setting (REDIS_START_URLS_BATCH_SIZE).
            self.redis_batch_size = settings.getint(
                'REDIS_START_URLS_BATCH_SIZE',
                settings.getint('CONCURRENT_REQUESTS'),
            )

        try:
            self.redis_batch_size = int(self.redis_batch_size)
        except (TypeError, ValueError):
            raise ValueError("redis_batch_size must be an integer")

        if self.redis_encoding is None:
            self.redis_encoding = settings.get('REDIS_ENCODING', defaults.REDIS_ENCODING)

        self.logger.info("Reading start URLs from redis key '%(redis_key)s' "
                        "(batch size: %(redis_batch_size)s, encoding: %(redis_encoding)s",
                        self.__dict__)

        self.server = connection.from_settings(crawler.settings)
        # The idle signal is called when the spider has no requests left,
        # that's when we will schedule new requests from redis queue
        crawler.signals.connect(self.spider_idle, signal=signals.spider_idle)

    def next_requests(self):
        """Returns a request to be scheduled or none."""
        use_set = self.settings.getbool('REDIS_START_URLS_AS_SET', defaults.START_URLS_AS_SET)
        fetch_one = self.server.spop if use_set else self.server.lpop
        # XXX: Do we need to use a timeout here?
        found = 0
        # TODO: Use redis pipeline execution.
        while found < self.redis_batch_size:
            data = fetch_one(self.redis_key)
            if not data:
                # Queue empty.
                break
            req = self.make_request_from_data(data)
            if req:
                yield req
                found += 1
            else:
                self.logger.debug("Request not made from data: %r", data)

        if found:
            self.logger.debug("Read %s requests from '%s'", found, self.redis_key)

    def make_request_from_data(self, data):
        """Returns a Request instance from data coming from Redis.

        By default, ``data`` is an encoded URL. You can override this method to
        provide your own message decoding.

        Parameters
        ----------
        data : bytes
            Message from redis.

        """
        url = bytes_to_str(data, self.redis_encoding)
        return self.make_requests_from_url(url)

    def schedule_next_requests(self):
        """Schedules a request if available"""
        # TODO: While there is capacity, schedule a batch of redis requests.
        for req in self.next_requests():
            self.crawler.engine.crawl(req, spider=self)

    def spider_idle(self):
        """Schedules a request if available, otherwise waits."""
        # XXX: Handle a sentinel to close the spider.
        self.schedule_next_requests()
        raise DontCloseSpider

class RedisSpider(RedisMixin, Spider):
    """Spider that reads urls from redis queue when idle.

    Attributes
    ----------
    redis_key : str (default: REDIS_START_URLS_KEY)
        Redis key where to fetch start URLs from..
    redis_batch_size : int (default: CONCURRENT_REQUESTS)
        Number of messages to fetch from redis on each attempt.
    redis_encoding : str (default: REDIS_ENCODING)
        Encoding to use when decoding messages from redis queue.

    Settings
    --------
    REDIS_START_URLS_KEY : str (default: "<spider.name>:start_urls")
        Default Redis key where to fetch start URLs from..
    REDIS_START_URLS_BATCH_SIZE : int (deprecated by CONCURRENT_REQUESTS)
        Default number of messages to fetch from redis on each attempt.
    REDIS_START_URLS_AS_SET : bool (default: False)
        Use SET operations to retrieve messages from the redis queue. If False,
        the messages are retrieve using the LPOP command.
    REDIS_ENCODING : str (default: "utf-8")
        Default encoding to use when decoding messages from redis queue.

    """

    @classmethod
    def from_crawler(self, crawler, *args, **kwargs):
        obj = super(RedisSpider, self).from_crawler(crawler, *args, **kwargs)
        obj.setup_redis(crawler)
        return obj

class RedisCrawlSpider(RedisMixin, CrawlSpider):
    """Spider that reads urls from redis queue when idle.

    Attributes
    ----------
    redis_key : str (default: REDIS_START_URLS_KEY)
        Redis key where to fetch start URLs from..
    redis_batch_size : int (default: CONCURRENT_REQUESTS)
        Number of messages to fetch from redis on each attempt.
    redis_encoding : str (default: REDIS_ENCODING)
        Encoding to use when decoding messages from redis queue.

    Settings
    --------
    REDIS_START_URLS_KEY : str (default: "<spider.name>:start_urls")
        Default Redis key where to fetch start URLs from..
    REDIS_START_URLS_BATCH_SIZE : int (deprecated by CONCURRENT_REQUESTS)
        Default number of messages to fetch from redis on each attempt.
    REDIS_START_URLS_AS_SET : bool (default: True)
        Use SET operations to retrieve messages from the redis queue.
    REDIS_ENCODING : str (default: "utf-8")
        Default encoding to use when decoding messages from redis queue.

    """

    @classmethod
    def from_crawler(self, crawler, *args, **kwargs):
        obj = super(RedisCrawlSpider, self).from_crawler(crawler, *args, **kwargs)
        obj.setup_redis(crawler)
        return obj

集成bloom-filter到scrapy-redis

下载相关模块

pip install mmh3

pip install redis

在utils中编写bloom-filter类，现实去重

# -*- coding: utf-8 -*-
import mmh3
import redis
import math
import time

class PyBloomFilter(object):
    # 内置100个随机种子
    SEEDS = [543, 460, 171, 876, 796, 607, 650, 81, 837, 545, 591, 946, 846, 521, 913, 636, 878, 735, 414, 372,
            344, 324, 223, 180, 327, 891, 798, 933, 493, 293, 836, 10, 6, 544, 924, 849, 438, 41, 862, 648, 338,
            465, 562, 693, 979, 52, 763, 103, 387, 374, 349, 94, 384, 680, 574, 480, 307, 580, 71, 535, 300, 53,
            481, 519, 644, 219, 686, 236, 424, 326, 244, 212, 909, 202, 951, 56, 812, 901, 926, 250, 507, 739, 371,
            63, 584, 154, 7, 284, 617, 332, 472, 140, 605, 262, 355, 526, 647, 923, 199, 518]

    # capacity是预先估计要去重的数量
    # error_rate表示错误率
    # conn表示redis的连接客户端
    # key表示在redis中的键的名字前缀
    def __init__(self, capacity=1000000000, error_rate=0.00000001, conn=None, key='BloomFilter'):
        self.m = math.ceil(capacity*math.log2(math.e)*math.log2(1/error_rate))      # 需要的总bit位数
        self.k = math.ceil(math.log1p(2)*self.m/capacity)                           # 需要最少的hash次数
        self.mem = math.ceil(self.m/8/1024/1024)                                    # 需要的多少M内存
        self.blocknum = math.ceil(self.mem/512)                                     # 需要多少个512M的内存块,value的第一个字符必须是ascii码，所有最多有256个内存块
        self.seeds = self.SEEDS[0:self.k]
        self.key = key
        self.N = 2**31-1
        self.redis = conn
        # print(self.mem)
        # print(self.k)

    def add(self, value):
        name = self.key + "_" + str(ord(value[0])%self.blocknum)
        hashs = self.get_hashs(value)
        for hash in hashs:
            self.redis.setbit(name, hash, 1)

    def is_exist(self, value):
        name = self.key + "_" + str(ord(value[0])%self.blocknum)
        hashs = self.get_hashs(value)
        exist = True
        for hash in hashs:
            exist = exist & self.redis.getbit(name, hash)
        return exist

    def get_hashs(self, value):
        hashs = list()
        for seed in self.seeds:
            hash = mmh3.hash(value, seed)
            if hash >= 0:
                hashs.append(hash)
            else:
                hashs.append(self.N - hash)
        return hashs

pool = redis.ConnectionPool(host='192.168.1.1', port=6379, db=0)
conn = redis.StrictRedis(connection_pool=pool)

if __name__ == "__main__":
    bf = PyBloomFilter(conn=conn)
    bf.add('www.jobbole.com')
    bf.add('www.zhihu.com')
    print(bf.is_exist('www.zhihu.com'))
    print(bf.is_exist('www.lagou.com'))

修改dupefilter源码，让它使用我们自定制的去重策略

import logging
import time

from scrapy.dupefilters import BaseDupeFilter
from scrapy.utils.request import request_fingerprint

from . import defaults
from .connection import get_redis_from_settings
from ScrapyRedisTest.utils.bloomfilter import conn, PyBloomFilter

logger = logging.getLogger(__name__)

# TODO: Rename class to RedisDupeFilter.
class RFPDupeFilter(BaseDupeFilter):
    """Redis-based request duplicates filter.

    This class can also be used with default Scrapy's scheduler.

    """

    logger = logger

    def __init__(self, server, key, debug=False):
        """Initialize the duplicates filter.

        Parameters
        ----------
        server : redis.StrictRedis
            The redis server instance.
        key : str
            Redis key Where to store fingerprints.
        debug : bool, optional
            Whether to log filtered requests.

        """
        self.server = server
        self.key = key
        self.debug = debug
        self.logdupes = True

        self.bf = PyBloomFilter(conn=conn, key=key)

    @classmethod
    def from_settings(cls, settings):
        """Returns an instance from given settings.

        This uses by default the key ``dupefilter:<timestamp>``. When using the
        ``scrapy_redis.scheduler.Scheduler`` class, this method is not used as
        it needs to pass the spider name in the key.

        Parameters
        ----------
        settings : scrapy.settings.Settings

        Returns
        -------
        RFPDupeFilter
            A RFPDupeFilter instance.

        """
        server = get_redis_from_settings(settings)
        # XXX: This creates one-time key. needed to support to use this
        # class as standalone dupefilter with scrapy's default scheduler
        # if scrapy passes spider on open() method this wouldn't be needed
        # TODO: Use SCRAPY_JOB env as default and fallback to timestamp.
        key = defaults.DUPEFILTER_KEY % {'timestamp': int(time.time())}
        debug = settings.getbool('DUPEFILTER_DEBUG')
        return cls(server, key=key, debug=debug)

    @classmethod
    def from_crawler(cls, crawler):
        """Returns instance from crawler.

        Parameters
        ----------
        crawler : scrapy.crawler.Crawler

        Returns
        -------
        RFPDupeFilter
            Instance of RFPDupeFilter.

        """
        return cls.from_settings(crawler.settings)

    def request_seen(self, request):
        """Returns True if request was already seen.

        Parameters
        ----------
        request : scrapy.http.Request

        Returns
        -------
        bool

        """
        fp = self.request_fingerprint(request)

        if self.bf.is_exist(fp):
            return True
        else:
            self.bf.add(fp)
            return False
        # This returns the number of values added, zero if already exists.
        # added = self.server.sadd(self.key, fp)
        # return added == 0

    def request_fingerprint(self, request):
        """Returns a fingerprint for a given request.

        Parameters
        ----------
        request : scrapy.http.Request

        Returns
        -------
        str

        """
        return request_fingerprint(request)

    def close(self, reason=''):
        """Delete data on close. Called by Scrapy's scheduler.

        Parameters
        ----------
        reason : str, optional

        """
        self.clear()

    def clear(self):
        """Clears fingerprints data."""
        self.server.delete(self.key)

    def log(self, request, spider):
        """Logs given request.

        Parameters
        ----------
        request : scrapy.http.Request
        spider : scrapy.spiders.Spider

        """
        if self.debug:
            msg = "Filtered duplicate request: %(request)s"
            self.logger.debug(msg, {'request': request}, extra={'spider': spider})
        elif self.logdupes:
            msg = ("Filtered duplicate request %(request)s"
                " - no more duplicates will be shown"
                " (see DUPEFILTER_DEBUG to show all duplicates)")
            self.logger.debug(msg, {'request': request}, extra={'spider': spider})
            self.logdupes = False