如何在Scrapy Splash中使用Crawlera lua脚本时获得session_id？

Question

如你所知，当我们尝试在Crawlera中使用Scrapy Splash时，我们使用这个lua脚本：

function use_crawlera(splash)
    -- Make sure you pass your Crawlera API key in the 'crawlera_user' arg.
    -- Have a look at the file spiders/quotes-js.py to see how to do it.
    -- Find your Crawlera credentials in https://app.scrapinghub.com/
    local user = splash.args.crawlera_user

    local host = 'proxy.crawlera.com'
    local port = 8010
    local session_header = 'X-Crawlera-Session'
    local session_id = 'create'

    splash:on_request(function (request)
        request:set_header('X-Crawlera-Cookies', 'disable')
        request:set_header(session_header, session_id)
        request:set_proxy{host, port, username=user, password=''}
    end)

    splash:on_response_headers(function (response)
        if type(response.headers[session_header]) ~= nil then
            session_id = response.headers[session_header]
        end
    end)
end

function main(splash)
    use_crawlera(splash)
        splash:init_cookies(splash.args.cookies)
        assert(splash:go{
            splash.args.url,
            headers=splash.args.headers,
            http_method=splash.args.http_method,
        })    
            assert(splash:wait(3))
        return {
            html = splash:html(),
            cookies = splash:get_cookies(),
        }
end

在这个lua脚本中有一个我非常需要的session_id变量，但是我如何从Scrapy的响应中访问它呢？

我尝试过response.session_id或response.headers['X-Crawlera-Session']，但两者都不起作用。

Answer 1

使用splash:set_result_header。

Answer 2

在您的lua脚本中，

1. 还返回HAR数据(https://splash.readthedocs.io/en/stable/scripting-ref.html#splash-har)：

    return {
        html = splash:html(),
        har = splash:har(),
        cookies = splash:get_cookies(),
    }

1. 假设您正在使用scrapy splash (https://github.com/scrapy-plugins/scrapy-splash)，请确保将execute端点设置为您的请求：

meta['splash']['endpoint'] = 'execute'。

如果使用scrapy.Request，则render.json是默认端点，但对于scrapy_splash.SplashRequest，默认端点是render.html。查看以下两个示例，了解如何设置端点：https://github.com/scrapy-plugins/scrapy-splash#requests

1. 现在您可以在您的解析方法中访问X-Crawlera-Session头：

    def parse(self, response):
        headers = json.loads(response.text)['har']['log']['entries'][0]['response']['headers']
        session_id = next(x for x in headers if x['name'] == 'X-Crawlera-Session')['value']

>>> headers = json.loads(response.text)['har']['log']['entries'][0]['response']['headers']
>>> next(x for x in headers if x['name'] == 'X-Crawlera-Session')
{u'name': u'X-Crawlera-Session', u'value': u'2124641382'}