Python Scrapy - 基于mimetype的过滤器,以避免非文本文件下载

Question

我有一个正在运行的scrapy项目,但它是带宽密集型的,因为它试图下载大量的二进制文件(zip,tar,mp3,.. etc).

我认为最好的解决方案是根据mimetype(Content-Type :) HTTP标头过滤请求.我查看了scrapy代码并找到了这个设置:

DOWNLOADER_HTTPCLIENTFACTORY = 'scrapy.core.downloader.webclient.ScrapyHTTPClientFactory'

我将其更改为:DOWNLOADER_HTTPCLIENTFACTORY ='myproject.webclients.ScrapyHTTPClientFactory'

并播放了一点ScrapyHTTPPageGetter,这里是编辑突出显示:

class ScrapyHTTPPageGetter(HTTPClient):
    # this is my edit
    def handleEndHeaders(self):
        if 'Content-Type' in self.headers.keys():
            mimetype = str(self.headers['Content-Type'])
            # Actually I need only the html, but just in 
            # case I've preserved all the text
            if mimetype.find('text/') > -1: 
                # Good, this page is needed
                self.factory.gotHeaders(self.headers)
            else:
                self.factory.noPage(Exception('Incorrect Content-Type'))

我觉得这是错的,在确定它是不需要的mimetype后,我需要更多scrapy友好的方式来取消/删除请求.而不是等待整个数据下载.

编辑:
我要求具体说明这部分self.factory.noPage(Exception('Incorrect Content-Type'))是取消请求的正确方法.

更新1:
我当前的设置已经破坏了Scrapy服务器,因此请不要尝试使用上面相同的代码来解决问题.

更新2:
我已经使用以下结构设置了一个基于Apache的网站进行测试:

/var/www/scrapper-test/Zend -> /var/www/scrapper-test/Zend.zip (symlink)
/var/www/scrapper-test/Zend.zip

我注意到Scrapy丢弃带有.zip扩展名的那些,但是在没有.zip的情况下丢弃它,即使它只是它的符号链接.

Answer 1

我构建了这个中间件,以排除任何不在正则表达式白名单中的响应类型:

from scrapy.http.response.html import HtmlResponse
from scrapy.exceptions import IgnoreRequest
from scrapy import log
import re

class FilterResponses(object):
    """Limit the HTTP response types that Scrapy dowloads."""

    @staticmethod
    def is_valid_response(type_whitelist, content_type_header):
        for type_regex in type_whitelist:
            if re.search(type_regex, content_type_header):
                return True
        return False

    def process_response(self, request, response, spider):
        """
        Only allow HTTP response types that that match the given list of 
        filtering regexs
        """
        # each spider must define the variable response_type_whitelist as an
        # iterable of regular expressions. ex. (r'text', )
        type_whitelist = getattr(spider, "response_type_whitelist", None)
        content_type_header = response.headers.get('content-type', None)
        if not type_whitelist:
            return response
        elif not content_type_header:
            log.msg("no content type header: {}".format(response.url), level=log.DEBUG, spider=spider)
            raise IgnoreRequest()
        elif self.is_valid_response(type_whitelist, content_type_header):
            log.msg("valid response {}".format(response.url), level=log.DEBUG, spider=spider)
            return response
        else:
            msg = "Ignoring request {}, content-type was not in whitelist".format(response.url)
            log.msg(msg, level=log.DEBUG, spider=spider)
            raise IgnoreRequest()

要使用它,请将其添加到settings.py:

DOWNLOADER_MIDDLEWARES = {
    '[project_name].middlewares.FilterResponses': 999,
}

Answer 2

解决方案是设置一个Node.js代理并配置Scrapy通过环境变量使用它http_proxy。

代理应该做的是：

• 从 Scrapy 获取 HTTP 请求并将其发送到正在爬取的服务器。然后它返回 Scrapy 的响应，即拦截所有 HTTP 流量。
• 对于二进制文件（基于您实施的启发式），它会403 Forbidden向 Scrapy 发送错误并立即关闭请求/响应。这有助于节省时间、流量，并且 Scrapy 不会崩溃。

示例代理代码

这确实有效！

http.createServer(function(clientReq, clientRes) {
    var options = {
        host: clientReq.headers['host'],
        port: 80,
        path: clientReq.url,
        method: clientReq.method,
        headers: clientReq.headers
    };


    var fullUrl = clientReq.headers['host'] + clientReq.url;
    
    var proxyReq = http.request(options, function(proxyRes) {
        var contentType = proxyRes.headers['content-type'] || '';
        if (!contentType.startsWith('text/')) {
            proxyRes.destroy();            
            var httpForbidden = 403;
            clientRes.writeHead(httpForbidden);
            clientRes.write('Binary download is disabled.');
            clientRes.end();
        }
        
        clientRes.writeHead(proxyRes.statusCode, proxyRes.headers);
        proxyRes.pipe(clientRes);
    });

    proxyReq.on('error', function(e) {
        console.log('problem with clientReq: ' + e.message);
    });

    proxyReq.end();
  
}).listen(8080);