Scrapy的指纹去重原理

指纹去重算法代码在scrapy.utils.request

def request_fingerprint(request, include_headers=None):
    if include_headers:
        include_headers = tuple(to_bytes(h.lower())
                                 for h in sorted(include_headers))
    cache = _fingerprint_cache.setdefault(request, {})
    if include_headers not in cache:
        fp = hashlib.sha1()
        fp.update(to_bytes(request.method))
        fp.update(to_bytes(canonicalize_url(request.url)))
        fp.update(request.body or b'')
        if include_headers:
            for hdr in include_headers:
                if hdr in request.headers:
                    fp.update(hdr)
                    for v in request.headers.getlist(hdr):
                        fp.update(v)
        cache[include_headers] = fp.hexdigest()
    return cache[include_headers]

指纹去重前提

request.dont_filter=False

指纹由何生成？

请求方法：request.method

请求地址：request.url

请求体：request.body

简而言之，根据请求方法、请求地址、请求体生成指纹，若指纹已存在则过滤，否则加入请求队列。