下载器中间件(Downloader Middleware)

下载器中间件是介于Scrapy的request/response处理的钩子框架。是用于全局修改Scrapy request和response的一个轻量、底层的系统。

激活下载器中间件

要激活下载器中间件组件，将其加入到 DOWNLOADER_MIDDLEWARES 设置中。该设置是一个字典(dict)，键为中间件类的路径，值为其中间件的顺序(order)。

这里是一个例子:

DOWNLOADER_MIDDLEWARES = {

    'myproject.middlewares.CustomDownloaderMiddleware': 543,

}

DOWNLOADER_MIDDLEWARES 设置会与Scrapy定义的 DOWNLOADER_MIDDLEWARES_BASE 设置合并(但不是覆盖)，而后根据顺序(order)进行排序，最后得到启用中间件的有序列表: 第一个中间件是最靠近引擎的，最后一个中间件是最靠近下载器的。

关于如何分配中间件的顺序请查看 DOWNLOADER_MIDDLEWARES_BASE 设置，而后根据您想要放置中间件的位置选择一个值。由于每个中间件执行不同的动作，您的中间件可能会依赖于之前(或者之后)执行的中间件，因此顺序是很重要的。

如果您想禁止内置的(在 DOWNLOADER_MIDDLEWARES_BASE 中设置并默认启用的)中间件，您必须在项目的 DOWNLOADER_MIDDLEWARES 设置中定义该中间件，并将其值赋为。例如，如果您想要关闭user-agent中间件:

DOWNLOADER_MIDDLEWARES = {

    'myproject.middlewares.CustomDownloaderMiddleware': 543,

    'scrapy.contrib.downloadermiddleware.useragent.UserAgentMiddleware': None,

}

最后，请注意，有些中间件需要通过特定的设置来启用。

编写您自己的下载器中间件

编写下载器中间件十分简单。每个中间件组件是一个定义了以下一个或多个方法的Python类:

class scrapy.contrib.downloadermiddleware.DownloaderMiddleware

1、process_request(request, spider)

当每个request通过下载中间件时，该方法被调用。

process_request() 必须返回其中之一: 返回 None 、返回一个 Response 对象、返回一个 Request 对象或raise IgnoreRequest 。

如果其返回 None ，Scrapy将继续处理该request，执行其他的中间件的相应方法，直到合适的下载器处理函数(download handler)被调用，该request被执行(其response被下载)。

如果其返回 Response 对象，Scrapy将不会调用任何其他的 process_request() 或 process_exception() 方法，或相应地下载函数；其将返回该response。已安装的中间件的 process_response() 方法则会在每个response返回时被调用。

如果其返回 Request 对象，Scrapy则停止调用 process_request方法并重新调度返回的request。当新返回的request被执行后，相应地中间件链将会根据下载的response被调用。

如果其raise一个 IgnoreRequest 异常，则安装的下载中间件的 process_exception() 方法会被调用。如果没有任何一个方法处理该异常，则request的errback(Request.errback)方法会被调用。如果没有代码处理抛出的异常，则该异常被忽略且不记录(不同于其他异常那样)。

参数:	request (`Request` 对象) – 处理的request spider (`Spider` 对象) – 该request对应的spider

操作演示：

输入指令：

scrapy startproject httpbintest

cd httpbintest

scrapy genspider httpbin httpbin.org

之后进入工程修改httpbin.py的内容，修改为：

import scrapy

class HttpbinSpider(scrapy.Spider):

    name = 'httpbin'

    allowed_domains = ['httpbin.org']

    start_urls = ['http://httpbin.org/']

    def parse(self, response):

        print(response.text)

输入scrapy crawl httpbin

打印后的结果为：

2018-10-11 12:04:53 [scrapy.utils.log] INFO: Scrapy 1.5.1 started (bot: httpbintest)

2018-10-11 12:04:53 [scrapy.utils.log] INFO: Versions: lxml 4.1.0.0, libxml2 2.9.4, cssselect 1.0.3, parsel 1.5.0, w3lib 1.19.0, Twisted 18.7.0, Python 3.6.3 |A

naconda custom (64-bit)| (default, Oct 15 2017, 03:27:45) [MSC v.1900 64 bit (AMD64)], pyOpenSSL 17.2.0 (OpenSSL 1.0.2p  14 Aug 2018), cryptography 2.0.3, Platf

orm Windows-7-6.1.7601-SP1

2018-10-11 12:04:53 [scrapy.crawler] INFO: Overridden settings: {'BOT_NAME': 'httpbintest', 'NEWSPIDER_MODULE': 'httpbintest.spiders', 'ROBOTSTXT_OBEY': True, '

SPIDER_MODULES': ['httpbintest.spiders']}

2018-10-11 12:04:54 [scrapy.middleware] INFO: Enabled extensions:

['scrapy.extensions.corestats.CoreStats',

 'scrapy.extensions.telnet.TelnetConsole',

 'scrapy.extensions.logstats.LogStats']

2018-10-11 12:04:55 [scrapy.middleware] INFO: Enabled downloader middlewares:

['scrapy.downloadermiddlewares.robotstxt.RobotsTxtMiddleware',

 'scrapy.downloadermiddlewares.httpauth.HttpAuthMiddleware',

 'scrapy.downloadermiddlewares.downloadtimeout.DownloadTimeoutMiddleware',

 'scrapy.downloadermiddlewares.defaultheaders.DefaultHeadersMiddleware',

 'scrapy.downloadermiddlewares.useragent.UserAgentMiddleware',

 'scrapy.downloadermiddlewares.retry.RetryMiddleware',

 'scrapy.downloadermiddlewares.redirect.MetaRefreshMiddleware',

 'scrapy.downloadermiddlewares.httpcompression.HttpCompressionMiddleware',

 'scrapy.downloadermiddlewares.redirect.RedirectMiddleware',

 'scrapy.downloadermiddlewares.cookies.CookiesMiddleware',

 'scrapy.downloadermiddlewares.httpproxy.HttpProxyMiddleware',

 'scrapy.downloadermiddlewares.stats.DownloaderStats']

2018-10-11 12:04:55 [scrapy.middleware] INFO: Enabled spider middlewares:

['scrapy.spidermiddlewares.httperror.HttpErrorMiddleware',

 'scrapy.spidermiddlewares.offsite.OffsiteMiddleware',

 'scrapy.spidermiddlewares.referer.RefererMiddleware',

 'scrapy.spidermiddlewares.urllength.UrlLengthMiddleware',

 'scrapy.spidermiddlewares.depth.DepthMiddleware']

2018-10-11 12:04:55 [scrapy.middleware] INFO: Enabled item pipelines:

[]

2018-10-11 12:04:55 [scrapy.core.engine] INFO: Spider opened

2018-10-11 12:04:55 [scrapy.extensions.logstats] INFO: Crawled 0 pages (at 0 pages/min), scraped 0 items (at 0 items/min)

2018-10-11 12:04:55 [scrapy.extensions.telnet] DEBUG: Telnet console listening on 127.0.0.1:6023

2018-10-11 12:04:56 [scrapy.core.engine] DEBUG: Crawled (200) <GET http://httpbin.org/robots.txt> (referer: None)

2018-10-11 12:04:58 [scrapy.core.engine] DEBUG: Crawled (200) <GET http://httpbin.org/> (referer: None)

<!DOCTYPE html>

<html lang="en">

<head>

    <meta charset="UTF-8">

    <title>httpbin.org</title>

    <link href="https://fonts.googleapis.com/css?family=Open+Sans:400,700|Source+Code+Pro:300,600|Titillium+Web:400,600,700"

        rel="stylesheet">

    <link rel="stylesheet" type="text/css" href="/flasgger_static/swagger-ui.css">

    <link rel="icon" type="image/png" href="/static/favicon.ico" sizes="64x64 32x32 16x16" />

    <style>

        html {

            box-sizing: border-box;

            overflow: -moz-scrollbars-vertical;

            overflow-y: scroll;

        }

        *,

        *:before,

        *:after {

            box-sizing: inherit;

        }

        body {

            margin: 0;

            background: #fafafa;

        }

    </style>

</head>

<body>

    <a href="https://github.com/requests/httpbin" class="github-corner" aria-label="View source on Github">

        <svg width="" height="" viewBox="0 0 250 250" style="fill:#151513; color:#fff; position: absolute; top: 0; border: 0; right: 0;"

            aria-hidden="true">

            <path d="M0,0 L115,115 L130,115 L142,142 L250,250 L250,0 Z"></path>

            <path d="M128.3,109.0 C113.8,99.7 119.0,89.6 119.0,89.6 C122.0,82.7 120.5,78.6 120.5,78.6 C119.2,72.0 123.4,76.3 123.4,76.3 C127.3,80.9 125.5,87.3 1

25.5,87.3 C122.9,97.6 130.6,101.9 134.4,103.2"

                fill="currentColor" style="transform-origin: 130px 106px;" class="octo-arm"></path>

            <path d="M115.0,115.0 C114.9,115.1 118.7,116.5 119.8,115.4 L133.7,101.6 C136.9,99.2 139.9,98.4 142.2,98.6 C133.8,88.0 127.5,74.4 143.8,58.0 C148.5,5

3.4 154.0,51.2 159.7,51.0 C160.3,49.4 163.2,43.6 171.4,40.1 C171.4,40.1 176.1,42.5 178.8,56.2 C183.1,58.6 187.2,61.8 190.9,65.4 C194.5,69.0 197.7,73.2 200.1,77.

6 C213.8,80.2 216.3,84.9 216.3,84.9 C212.7,93.1 206.9,96.0 205.4,96.6 C205.1,102.4 203.0,107.8 198.3,112.5 C181.9,128.9 168.3,122.5 157.7,114.1 C157.9,116.9 156

.7,120.9 152.7,124.9 L141.0,136.5 C139.8,137.7 141.6,141.9 141.8,141.8 Z"

                fill="currentColor" class="octo-body"></path>

        </svg>

    </a>

    <svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" style="position:absolute;width:0;height:0">

        <defs>

            <symbol viewBox="0 0 20 20" id="unlocked">

                <path d="M15.8 8H14V5.6C14 2.703 12.665 1 10 1 7.334 1 6 2.703 6 5.6V6h2v-.801C8 3.754 8.797 3 10 3c1.203 0 2 .754 2 2.199V8H4c-.553 0-1 .646-1

1.199V17c0 .549.428 1.139.951 1.307l1.197.387C5.672 18.861 6.55 19 7.1 19h5.8c.549 0 1.428-.139 1.951-.307l1.196-.387c.524-.167.953-.757.953-1.306V9.199C17 8.64

6 16.352 8 15.8 8z"></path>

            </symbol>

            <symbol viewBox="0 0 20 20" id="locked">

                <path d="M15.8 8H14V5.6C14 2.703 12.665 1 10 1 7.334 1 6 2.703 6 5.6V8H4c-.553 0-1 .646-1 1.199V17c0 .549.428 1.139.951 1.307l1.197.387C5.672 18

.861 6.55 19 7.1 19h5.8c.549 0 1.428-.139 1.951-.307l1.196-.387c.524-.167.953-.757.953-1.306V9.199C17 8.646 16.352 8 15.8 8zM12 8H8V5.199C8 3.754 8.797 3 10 3c1

.203 0 2 .754 2 2.199V8z"

                />

            </symbol>

            <symbol viewBox="0 0 20 20" id="close">

                <path d="M14.348 14.849c-.469.469-1.229.469-1.697 0L10 11.819l-2.651 3.029c-.469.469-1.229.469-1.697 0-.469-.469-.469-1.229 0-1.697l2.758-3.15-2

.759-3.152c-.469-.469-.469-1.228 0-1.697.469-.469 1.228-.469 1.697 0L10 8.183l2.651-3.031c.469-.469 1.228-.469 1.697 0 .469.469.469 1.229 0 1.697l-2.758 3.152 2

.758 3.15c.469.469.469 1.229 0 1.698z"

                />

            </symbol>

            <symbol viewBox="0 0 20 20" id="large-arrow">

                <path d="M13.25 10L6.109 2.58c-.268-.27-.268-.707 0-.979.268-.27.701-.27.969 0l7.83 7.908c.268.271.268.709 0 .979l-7.83 7.908c-.268.271-.701.27-

.969 0-.268-.269-.268-.707 0-.979L13.25 10z"

                />

            </symbol>

            <symbol viewBox="0 0 20 20" id="large-arrow-down">

                <path d="M17.418 6.109c.272-.268.709-.268.979 0s.271.701 0 .969l-7.908 7.83c-.27.268-.707.268-.979 0l-7.908-7.83c-.27-.268-.27-.701 0-.969.271-.

268.709-.268.979 0L10 13.25l7.418-7.141z"

                />

            </symbol>

            <symbol viewBox="0 0 24 24" id="jump-to">

                <path d="M19 7v4H5.83l3.58-3.59L8 6l-6 6 6 6 1.41-1.41L5.83 13H21V7z" />

            </symbol>

            <symbol viewBox="0 0 24 24" id="expand">

                <path d="M10 18h4v-2h-4v2zM3 6v2h18V6H3zm3 7h12v-2H6v2z" />

            </symbol>

        </defs>

    </svg>

    <div id="swagger-ui">

        <div data-reactroot="" class="swagger-ui">

            <div>

                <div class="information-container wrapper">

                    <section class="block col-12">

                        <div class="info">

                            <hgroup class="main">

                                <h2 class="title">httpbin.org

                                    <small>

                                        <pre class="version">0.9.2</pre>

                                    </small>

                                </h2>

                                <pre class="base-url">[ Base URL: httpbin.org/ ]</pre>

                            </hgroup>

                            <div class="description">

                                <div class="markdown">

                                    <p>A simple HTTP Request &amp; Response Service.

                                        <br>

                                        <br>

                                        <b>Run locally: </b>

                                        <code>$ docker run -p 80:80 kennethreitz/httpbin</code>

                                    </p>

                                </div>

                            </div>

                            <div>

                                <div>

                                    <a href="https://kennethreitz.org" target="_blank">the developer - Website</a>

                                </div>

                                <a href="mailto:[email protected]">Send email to the developer</a>

                            </div>

                        </div>

                        <!-- ADDS THE LOADER SPINNER -->

                        <div class="loading-container">

                            <div class="loading"></div>

                        </div>

                    </section>

                </div>

            </div>

        </div>

    </div>

    <div class='swagger-ui'>

        <div class="wrapper">

            <section class="clear">

                <span style="float: right;">

                    [Powered by

                    <a target="_blank" href="https://github.com/rochacbruno/flasgger">Flasgger</a>]

                    <br>

                </span>

            </section>

        </div>

    </div>

    <script src="/flasgger_static/swagger-ui-bundle.js"> </script>

    <script src="/flasgger_static/swagger-ui-standalone-preset.js"> </script>

    <script src='/flasgger_static/%20lib/jquery.min.js' type='text/javascript'></script>

    <script>

        window.onload = function () {

            fetch("/spec.json")

                .then(function (response) {

                    response.json()

                        .then(function (json) {

                            var current_protocol = window.location.protocol.slice(0, -1);

                            if (json.schemes[0] != current_protocol) {

                                // Switches scheme to the current in use

                                var other_protocol = json.schemes[0];

                                json.schemes[0] = current_protocol;

                                json.schemes[1] = other_protocol;

                            }

                            json.host = window.location.host;  // sets the current host

                            const ui = SwaggerUIBundle({

                                spec: json,

                                validatorUrl: null,

                                dom_id: '#swagger-ui',

                                deepLinking: true,

                                jsonEditor: true,

                                docExpansion: "none",

                                apisSorter: "alpha",

                                //operationsSorter: "alpha",

                                presets: [

                                    SwaggerUIBundle.presets.apis,

                                    // yay ES6 modules ↘

                                    Array.isArray(SwaggerUIStandalonePreset) ? SwaggerUIStandalonePreset : SwaggerUIStandalonePreset.default

                                ],

                                plugins: [

                                    SwaggerUIBundle.plugins.DownloadUrl

                                ],

            // layout: "StandaloneLayout"  // uncomment to enable the green top header

        })

        window.ui = ui

        // uncomment to rename the top brand if layout is enabled

        // $(".topbar-wrapper .link span").replaceWith("<span>httpbin</span>");

        })

    })

}

    </script>

<script type="text/javascript">

  var _gauges = _gauges || [];

  (function() {

    var t   = document.createElement('script');

    t.type  = 'text/javascript';

    t.async = true;

    t.id    = 'gauges-tracker';

    t.setAttribute('data-site-id', '58cb2e71c88d9043ac01d000');

    t.setAttribute('data-track-path', 'https://track.gaug.es/track.gif');

    t.src = 'https://d36ee2fcip1434.cloudfront.net/track.js';

    var s = document.getElementsByTagName('script')[0];

    s.parentNode.insertBefore(t, s);

  })();

</script>  <div class='swagger-ui'>

    <div class="wrapper">

        <section class="block col-12 block-desktop col-12-desktop">

            <div>

                <h2>Other Utilities</h2>

                <ul>

                    <li>

                        <a href="/forms/post">HTML form</a> that posts to /post /forms/post</li>

                </ul>

                <br />

                <br />

            </div>

        </section>

    </div>

</div>

</body>

</html>

2018-10-11 12:04:58 [scrapy.core.engine] INFO: Closing spider (finished)

2018-10-11 12:04:58 [scrapy.statscollectors] INFO: Dumping Scrapy stats:

{'downloader/request_bytes': 430,

 'downloader/request_count': 2,

 'downloader/request_method_count/GET': 2,

 'downloader/response_bytes': 10556,

 'downloader/response_count': 2,

 'downloader/response_status_count/200': 2,

 'finish_reason': 'finished',

 'finish_time': datetime.datetime(2018, 10, 11, 4, 4, 58, 747159),

 'log_count/DEBUG': 3,

 'log_count/INFO': 7,

 'response_received_count': 2,

 'scheduler/dequeued': 1,

 'scheduler/dequeued/memory': 1,

 'scheduler/enqueued': 1,

 'scheduler/enqueued/memory': 1,

 'start_time': datetime.datetime(2018, 10, 11, 4, 4, 55, 342964)}

2018-10-11 12:04:58 [scrapy.core.engine] INFO: Spider closed (finished)

查看打印后的结果，我们发现有一个"origin": "221.208.253.90",的这行代码，我们通过上网查询发现这个本地的IP地址为：黑龙江省哈尔滨市联通，那么现在想做的是做一个代理的中间件，实现一个IP的伪装

现在我们需要在middleware.py这个文件编写代码了，其代码如下：

class ProxyMiddleware(object): # 代理中间件

    logger = logging.getLogger(__name__) # 利用这个可以方便进行scrapy 的log输出

    def process_request(self,request, spider):

        self.logger.debug('Using Proxy')

        request.meta['proxy'] = 'http://211.101.136.86:49784' # 设置request的代理，如果请求的时候，request会自动加上这个代理 
        return None

根据上文需要，所以在settings.py的文件里写入代码。其代码如下：

DOWNLOADER_MIDDLEWARES = {

   'httpbintest.middlewares.ProxyMiddleware': 543,

}

然后敲入指令scrapy crawl httpbin

其打印结果为：

2018-10-11 14:16:58 [scrapy.utils.log] INFO: Scrapy 1.5.1 started (bot: httpbintest)

2018-10-11 14:16:58 [scrapy.utils.log] INFO: Versions: lxml 4.1.0.0, libxml2 2.9.4, cssselect 1.0.3, parsel 1.5.0, w3lib 1.19.0, Twisted 18.7.0, Python 3.6.3 |A

naconda custom (64-bit)| (default, Oct 15 2017, 03:27:45) [MSC v.1900 64 bit (AMD64)], pyOpenSSL 17.2.0 (OpenSSL 1.0.2p  14 Aug 2018), cryptography 2.0.3, Platf

orm Windows-7-6.1.7601-SP1

2018-10-11 14:16:58 [scrapy.crawler] INFO: Overridden settings: {'BOT_NAME': 'httpbintest', 'NEWSPIDER_MODULE': 'httpbintest.spiders', 'ROBOTSTXT_OBEY': True, '

SPIDER_MODULES': ['httpbintest.spiders']}

2018-10-11 14:16:58 [scrapy.middleware] INFO: Enabled extensions:

['scrapy.extensions.corestats.CoreStats',

 'scrapy.extensions.telnet.TelnetConsole',

 'scrapy.extensions.logstats.LogStats']

2018-10-11 14:16:59 [scrapy.middleware] INFO: Enabled downloader middlewares:

['scrapy.downloadermiddlewares.robotstxt.RobotsTxtMiddleware',

 'scrapy.downloadermiddlewares.httpauth.HttpAuthMiddleware',

 'scrapy.downloadermiddlewares.downloadtimeout.DownloadTimeoutMiddleware',

 'scrapy.downloadermiddlewares.defaultheaders.DefaultHeadersMiddleware',

 'scrapy.downloadermiddlewares.useragent.UserAgentMiddleware',

 'httpbintest.middlewares.ProxyMiddleware',

 'scrapy.downloadermiddlewares.retry.RetryMiddleware',

 'scrapy.downloadermiddlewares.redirect.MetaRefreshMiddleware',

 'scrapy.downloadermiddlewares.httpcompression.HttpCompressionMiddleware',

 'scrapy.downloadermiddlewares.redirect.RedirectMiddleware',

 'scrapy.downloadermiddlewares.cookies.CookiesMiddleware',

 'scrapy.downloadermiddlewares.httpproxy.HttpProxyMiddleware',

 'scrapy.downloadermiddlewares.stats.DownloaderStats']

2018-10-11 14:16:59 [scrapy.middleware] INFO: Enabled spider middlewares:

['scrapy.spidermiddlewares.httperror.HttpErrorMiddleware',

 'scrapy.spidermiddlewares.offsite.OffsiteMiddleware',

 'scrapy.spidermiddlewares.referer.RefererMiddleware',

 'scrapy.spidermiddlewares.urllength.UrlLengthMiddleware',

 'scrapy.spidermiddlewares.depth.DepthMiddleware']

2018-10-11 14:16:59 [scrapy.middleware] INFO: Enabled item pipelines:

[]

2018-10-11 14:16:59 [scrapy.core.engine] INFO: Spider opened

2018-10-11 14:16:59 [scrapy.extensions.logstats] INFO: Crawled 0 pages (at 0 pages/min), scraped 0 items (at 0 items/min)

2018-10-11 14:16:59 [scrapy.extensions.telnet] DEBUG: Telnet console listening on 127.0.0.1:6023

2018-10-11 14:16:59 [httpbintest.middlewares] DEBUG: Using Proxy

2018-10-11 14:16:59 [scrapy.core.engine] DEBUG: Crawled (200) <GET http://httpbin.org/robots.txt> (referer: None)

2018-10-11 14:16:59 [httpbintest.middlewares] DEBUG: Using Proxy

2018-10-11 14:17:00 [scrapy.core.engine] DEBUG: Crawled (200) <GET http://httpbin.org/get> (referer: None)

{

  "args": {},

  "headers": {

    "Accept": "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8",

    "Accept-Encoding": "gzip,deflate",

    "Accept-Language": "en",

    "Connection": "close",

    "Host": "httpbin.org",

    "User-Agent": "Scrapy/1.5.1 (+https://scrapy.org)"

  },

  "origin": "211.101.136.86",

  "url": "http://httpbin.org/get"

}

2018-10-11 14:17:00 [scrapy.core.engine] INFO: Closing spider (finished)

2018-10-11 14:17:00 [scrapy.statscollectors] INFO: Dumping Scrapy stats:

{'downloader/request_bytes': 433,

 'downloader/request_count': 2,

 'downloader/request_method_count/GET': 2,

 'downloader/response_bytes': 794,

 'downloader/response_count': 2,

 'downloader/response_status_count/200': 2,

 'finish_reason': 'finished',

 'finish_time': datetime.datetime(2018, 10, 11, 6, 17, 0, 472256),

 'log_count/DEBUG': 5,

 'log_count/INFO': 7,

 'response_received_count': 2,

 'scheduler/dequeued': 1,

 'scheduler/dequeued/memory': 1,

 'scheduler/enqueued': 1,

 'scheduler/enqueued/memory': 1,

 'start_time': datetime.datetime(2018, 10, 11, 6, 16, 59, 96177)}

2018-10-11 14:17:00 [scrapy.core.engine] INFO: Spider closed (finished)

2、process_response(request, response, spider)

process_request() 必须返回以下之一: 返回一个 Response 对象、返回一个 Request 对象或raise一个 IgnoreRequest 异常。

如果其返回一个 Response (可以与传入的response相同，也可以是全新的对象)，该response会被在链中的其他中间件的 process_response() 方法处理。

如果其返回一个 Request 对象，则中间件链停止，返回的request会被重新调度下载。处理类似于 process_request() 返回request所做的那样。

如果其抛出一个 IgnoreRequest 异常，则调用request的errback(Request.errback)。如果没有代码处理抛出的异常，则该异常被忽略且不记录(不同于其他异常那样)。

参数:	request (`Request` 对象) – response所对应的request response (`Response` 对象) – 被处理的response spider (`Spider` 对象) – response所对应的spider

现在我们在middlewares.py里写入代码，如下：

class ProxyMiddleware(object): # 代理中间件

    logger = logging.getLogger(__name__) # 利用这个可以方便进行scrapy 的log输出

    def process_request(self,request, spider):

        self.logger.debug('Using Proxy')

        request.meta['proxy'] = 'http://211.101.136.86:49784' # 设置request的代理，如果请求的时候，request会自动加上这个代理

    def process_response(self,request, response, spider):

        response.status = 201

        return response

在httpbin.py里写入：

import scrapy

class HttpbinSpider(scrapy.Spider):

    name = 'httpbin'

    allowed_domains = ['httpbin.org']

    start_urls = ['http://httpbin.org/get']

    def parse(self, response):

        print(response.text)

        print(response.status)

输入scrapy crawl httpbin，看下打印的结果为：

2018-10-11 14:16:58 [scrapy.utils.log] INFO: Scrapy 1.5.1 started (bot: httpbintest)

2018-10-11 14:16:58 [scrapy.utils.log] INFO: Versions: lxml 4.1.0.0, libxml2 2.9.4, cssselect 1.0.3, parsel 1.5.0, w3lib 1.19.0, Twisted 18.7.0, Python 3.6.3 |A

naconda custom (64-bit)| (default, Oct 15 2017, 03:27:45) [MSC v.1900 64 bit (AMD64)], pyOpenSSL 17.2.0 (OpenSSL 1.0.2p  14 Aug 2018), cryptography 2.0.3, Platf

orm Windows-7-6.1.7601-SP1

2018-10-11 14:16:58 [scrapy.crawler] INFO: Overridden settings: {'BOT_NAME': 'httpbintest', 'NEWSPIDER_MODULE': 'httpbintest.spiders', 'ROBOTSTXT_OBEY': True, '

SPIDER_MODULES': ['httpbintest.spiders']}

2018-10-11 14:16:58 [scrapy.middleware] INFO: Enabled extensions:

['scrapy.extensions.corestats.CoreStats',

 'scrapy.extensions.telnet.TelnetConsole',

 'scrapy.extensions.logstats.LogStats']

2018-10-11 14:16:59 [scrapy.middleware] INFO: Enabled downloader middlewares:

['scrapy.downloadermiddlewares.robotstxt.RobotsTxtMiddleware',

 'scrapy.downloadermiddlewares.httpauth.HttpAuthMiddleware',

 'scrapy.downloadermiddlewares.downloadtimeout.DownloadTimeoutMiddleware',

 'scrapy.downloadermiddlewares.defaultheaders.DefaultHeadersMiddleware',

 'scrapy.downloadermiddlewares.useragent.UserAgentMiddleware',

 'httpbintest.middlewares.ProxyMiddleware',

 'scrapy.downloadermiddlewares.retry.RetryMiddleware',

 'scrapy.downloadermiddlewares.redirect.MetaRefreshMiddleware',

 'scrapy.downloadermiddlewares.httpcompression.HttpCompressionMiddleware',

 'scrapy.downloadermiddlewares.redirect.RedirectMiddleware',

 'scrapy.downloadermiddlewares.cookies.CookiesMiddleware',

 'scrapy.downloadermiddlewares.httpproxy.HttpProxyMiddleware',

 'scrapy.downloadermiddlewares.stats.DownloaderStats']

2018-10-11 14:16:59 [scrapy.middleware] INFO: Enabled spider middlewares:

['scrapy.spidermiddlewares.httperror.HttpErrorMiddleware',

 'scrapy.spidermiddlewares.offsite.OffsiteMiddleware',

 'scrapy.spidermiddlewares.referer.RefererMiddleware',

 'scrapy.spidermiddlewares.urllength.UrlLengthMiddleware',

 'scrapy.spidermiddlewares.depth.DepthMiddleware']

2018-10-11 14:16:59 [scrapy.middleware] INFO: Enabled item pipelines:

[]

2018-10-11 14:16:59 [scrapy.core.engine] INFO: Spider opened

2018-10-11 14:16:59 [scrapy.extensions.logstats] INFO: Crawled 0 pages (at 0 pages/min), scraped 0 items (at 0 items/min)

2018-10-11 14:16:59 [scrapy.extensions.telnet] DEBUG: Telnet console listening on 127.0.0.1:6023

2018-10-11 14:16:59 [httpbintest.middlewares] DEBUG: Using Proxy

2018-10-11 14:16:59 [scrapy.core.engine] DEBUG: Crawled (200) <GET http://httpbin.org/robots.txt> (referer: None)

2018-10-11 14:16:59 [httpbintest.middlewares] DEBUG: Using Proxy

2018-10-11 14:17:00 [scrapy.core.engine] DEBUG: Crawled (200) <GET http://httpbin.org/get> (referer: None)

{

  "args": {},

  "headers": {

    "Accept": "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8",

    "Accept-Encoding": "gzip,deflate",

    "Accept-Language": "en",

    "Connection": "close",

    "Host": "httpbin.org",

    "User-Agent": "Scrapy/1.5.1 (+https://scrapy.org)"

  },

  "origin": "211.101.136.86",

  "url": "http://httpbin.org/get"

}

2018-10-11 14:17:00 [scrapy.core.engine] INFO: Closing spider (finished)

2018-10-11 14:17:00 [scrapy.statscollectors] INFO: Dumping Scrapy stats:

{'downloader/request_bytes': 433,

 'downloader/request_count': 2,

 'downloader/request_method_count/GET': 2,

 'downloader/response_bytes': 794,

 'downloader/response_count': 2,

 'downloader/response_status_count/200': 2,

 'finish_reason': 'finished',

 'finish_time': datetime.datetime(2018, 10, 11, 6, 17, 0, 472256),

 'log_count/DEBUG': 5,

 'log_count/INFO': 7,

 'response_received_count': 2,

 'scheduler/dequeued': 1,

 'scheduler/dequeued/memory': 1,

 'scheduler/enqueued': 1,

 'scheduler/enqueued/memory': 1,

 'start_time': datetime.datetime(2018, 10, 11, 6, 16, 59, 96177)}

2018-10-11 14:17:00 [scrapy.core.engine] INFO: Spider closed (finished)

C:\Users\Administrator\Desktop\爬虫程序\Scrapy\httpbintest>scrapy crawl httpbin

2018-10-11 14:50:40 [scrapy.utils.log] INFO: Scrapy 1.5.1 started (bot: httpbintest)

2018-10-11 14:50:40 [scrapy.utils.log] INFO: Versions: lxml 4.1.0.0, libxml2 2.9.4, cssselect 1.0.3, parsel 1.5.0, w3lib 1.19.0, Twisted 18.7.0, Python 3.6.3 |A

naconda custom (64-bit)| (default, Oct 15 2017, 03:27:45) [MSC v.1900 64 bit (AMD64)], pyOpenSSL 17.2.0 (OpenSSL 1.0.2p  14 Aug 2018), cryptography 2.0.3, Platf

orm Windows-7-6.1.7601-SP1

2018-10-11 14:50:40 [scrapy.crawler] INFO: Overridden settings: {'BOT_NAME': 'httpbintest', 'NEWSPIDER_MODULE': 'httpbintest.spiders', 'ROBOTSTXT_OBEY': True, '

SPIDER_MODULES': ['httpbintest.spiders']}

2018-10-11 14:50:40 [scrapy.middleware] INFO: Enabled extensions:

['scrapy.extensions.corestats.CoreStats',

 'scrapy.extensions.telnet.TelnetConsole',

 'scrapy.extensions.logstats.LogStats']

2018-10-11 14:50:40 [scrapy.middleware] INFO: Enabled downloader middlewares:

['scrapy.downloadermiddlewares.robotstxt.RobotsTxtMiddleware',

 'scrapy.downloadermiddlewares.httpauth.HttpAuthMiddleware',

 'scrapy.downloadermiddlewares.downloadtimeout.DownloadTimeoutMiddleware',

 'scrapy.downloadermiddlewares.defaultheaders.DefaultHeadersMiddleware',

 'scrapy.downloadermiddlewares.useragent.UserAgentMiddleware',

 'httpbintest.middlewares.ProxyMiddleware',

 'scrapy.downloadermiddlewares.retry.RetryMiddleware',

 'scrapy.downloadermiddlewares.redirect.MetaRefreshMiddleware',

 'scrapy.downloadermiddlewares.httpcompression.HttpCompressionMiddleware',

 'scrapy.downloadermiddlewares.redirect.RedirectMiddleware',

 'scrapy.downloadermiddlewares.cookies.CookiesMiddleware',

 'scrapy.downloadermiddlewares.httpproxy.HttpProxyMiddleware',

 'scrapy.downloadermiddlewares.stats.DownloaderStats']

2018-10-11 14:50:40 [scrapy.middleware] INFO: Enabled spider middlewares:

['scrapy.spidermiddlewares.httperror.HttpErrorMiddleware',

 'scrapy.spidermiddlewares.offsite.OffsiteMiddleware',

 'scrapy.spidermiddlewares.referer.RefererMiddleware',

 'scrapy.spidermiddlewares.urllength.UrlLengthMiddleware',

 'scrapy.spidermiddlewares.depth.DepthMiddleware']

2018-10-11 14:50:40 [scrapy.middleware] INFO: Enabled item pipelines:

[]

2018-10-11 14:50:40 [scrapy.core.engine] INFO: Spider opened

2018-10-11 14:50:40 [scrapy.extensions.logstats] INFO: Crawled 0 pages (at 0 pages/min), scraped 0 items (at 0 items/min)

2018-10-11 14:50:40 [scrapy.extensions.telnet] DEBUG: Telnet console listening on 127.0.0.1:6023

2018-10-11 14:50:40 [httpbintest.middlewares] DEBUG: Using Proxy

2018-10-11 14:50:41 [scrapy.core.engine] DEBUG: Crawled (201) <GET http://httpbin.org/robots.txt> (referer: None)

2018-10-11 14:50:41 [httpbintest.middlewares] DEBUG: Using Proxy

2018-10-11 14:50:41 [scrapy.core.engine] DEBUG: Crawled (201) <GET http://httpbin.org/get> (referer: None)

{

  "args": {},

  "headers": {

    "Accept": "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8",

    "Accept-Encoding": "gzip,deflate",

    "Accept-Language": "en",

    "Connection": "close",

    "Host": "httpbin.org",

    "User-Agent": "Scrapy/1.5.1 (+https://scrapy.org)"

  },

  "origin": "211.101.136.86",

  "url": "http://httpbin.org/get"

}

201

2018-10-11 14:50:41 [scrapy.core.engine] INFO: Closing spider (finished)

2018-10-11 14:50:41 [scrapy.statscollectors] INFO: Dumping Scrapy stats:

{'downloader/request_bytes': 433,

 'downloader/request_count': 2,

 'downloader/request_method_count/GET': 2,

 'downloader/response_bytes': 794,

 'downloader/response_count': 2,

 'downloader/response_status_count/200': 2,

 'finish_reason': 'finished',

 'finish_time': datetime.datetime(2018, 10, 11, 6, 50, 41, 966878),

 'log_count/DEBUG': 5,

 'log_count/INFO': 7,

 'response_received_count': 2,

 'scheduler/dequeued': 1,

 'scheduler/dequeued/memory': 1,

 'scheduler/enqueued': 1,

 'scheduler/enqueued/memory': 1,

 'start_time': datetime.datetime(2018, 10, 11, 6, 50, 40, 436791)}

2018-10-11 14:50:41 [scrapy.core.engine] INFO: Spider closed (finished)

我们可以看到这一行代码：

爬虫--Scrapy之Downloader Middleware-LMLPHP

输出了 201状态码，那么这里实际上就是说downloader得到了request之后，然后记过middewire改写把状态码变成了201，然后再传给response，那么我们得到的状态码就变成了201

3、process_exception(request, exception, spider)

当下载处理器(download handler)或 process_request() (下载中间件)抛出异常(包括 IgnoreRequest 异常)时， Scrapy调用 process_exception() 。

process_exception() 应该返回以下之一: 返回 None 、一个 Response 对象、或者一个 Request 对象。

如果其返回 None ，Scrapy将会继续处理该异常，接着调用已安装的其他中间件的process_exception() 方法，直到所有中间件都被调用完毕，则调用默认的异常处理。

如果其返回一个 Response 对象，则已安装的中间件链的 process_response() 方法被调用。Scrapy将不会调用任何其他中间件的 process_exception() 方法。

如果其返回一个 Request 对象，则返回的request将会被重新调用下载。这将停止中间件的process_exception() 方法执行，就如返回一个response的那样。

参数:	request (是 `Request` 对象) – 产生异常的request exception (`Exception` 对象) – 抛出的异常 spider (`Spider` 对象) – request对应的spider

我们敲入代码，用一个代理对google进行爬取，先敲入 scrapy genspider google www.google.com ，在spiders里会有个google.py文件，为了防止不必要的麻烦，所以在settings.py里将ROBOTSTXT_OBEY 设置为False

现在我们在google.py里敲入代码：

# -*- coding: utf-8 -*-

import scrapy

class GoogleSpider(scrapy.Spider):

    name = 'google'

    allowed_domains = ['www.google.com']

    start_urls = ['http://www.google.com/']

    def make_requests_from_url(self, url):

        return scrapy.Request(url = url,meta={'download_timeout':10},callback=self.parse) # 设置超时时间

    def parse(self, response):

        print(response.text)

并在middlewares.py里添加代码为：

class ProxyMiddleware(object): # 代理中间件

    logger = logging.getLogger(__name__) # 利用这个可以方便进行scrapy 的log输出

    def process_exception(self,request, exception, spider):

        return request

输入scrapy crawl google，查看输出的内容为：

2018-10-11 16:21:07 [scrapy.utils.log] INFO: Scrapy 1.5.1 started (bot: httpbintest)

2018-10-11 16:21:07 [scrapy.utils.log] INFO: Versions: lxml 4.1.0.0, libxml2 2.9.4, cssselect 1.0.3, parsel 1.5.0, w3lib 1.19.0, Twisted 18.7.0, Python 3.6.3 |A

naconda custom (64-bit)| (default, Oct 15 2017, 03:27:45) [MSC v.1900 64 bit (AMD64)], pyOpenSSL 17.2.0 (OpenSSL 1.0.2p  14 Aug 2018), cryptography 2.0.3, Platf

orm Windows-7-6.1.7601-SP1

2018-10-11 16:21:07 [scrapy.crawler] INFO: Overridden settings: {'BOT_NAME': 'httpbintest', 'NEWSPIDER_MODULE': 'httpbintest.spiders', 'SPIDER_MODULES': ['httpb

intest.spiders']}

2018-10-11 16:21:07 [scrapy.middleware] INFO: Enabled extensions:

['scrapy.extensions.corestats.CoreStats',

 'scrapy.extensions.telnet.TelnetConsole',

 'scrapy.extensions.logstats.LogStats']

2018-10-11 16:21:08 [scrapy.middleware] INFO: Enabled downloader middlewares:

['scrapy.downloadermiddlewares.httpauth.HttpAuthMiddleware',

 'scrapy.downloadermiddlewares.downloadtimeout.DownloadTimeoutMiddleware',

 'scrapy.downloadermiddlewares.defaultheaders.DefaultHeadersMiddleware',

 'scrapy.downloadermiddlewares.useragent.UserAgentMiddleware',

 'httpbintest.middlewares.ProxyMiddleware',

 'scrapy.downloadermiddlewares.retry.RetryMiddleware',

 'scrapy.downloadermiddlewares.redirect.MetaRefreshMiddleware',

 'scrapy.downloadermiddlewares.httpcompression.HttpCompressionMiddleware',

 'scrapy.downloadermiddlewares.redirect.RedirectMiddleware',

 'scrapy.downloadermiddlewares.cookies.CookiesMiddleware',

 'scrapy.downloadermiddlewares.httpproxy.HttpProxyMiddleware',

 'scrapy.downloadermiddlewares.stats.DownloaderStats']

2018-10-11 16:21:08 [scrapy.middleware] INFO: Enabled spider middlewares:

['scrapy.spidermiddlewares.httperror.HttpErrorMiddleware',

 'scrapy.spidermiddlewares.offsite.OffsiteMiddleware',

 'scrapy.spidermiddlewares.referer.RefererMiddleware',

 'scrapy.spidermiddlewares.urllength.UrlLengthMiddleware',

 'scrapy.spidermiddlewares.depth.DepthMiddleware']

2018-10-11 16:21:08 [scrapy.middleware] INFO: Enabled item pipelines:

[]

2018-10-11 16:21:08 [scrapy.core.engine] INFO: Spider opened

2018-10-11 16:21:08 [scrapy.extensions.logstats] INFO: Crawled 0 pages (at 0 pages/min), scraped 0 items (at 0 items/min)

2018-10-11 16:21:08 [scrapy.extensions.telnet] DEBUG: Telnet console listening on 127.0.0.1:6023

2018-10-11 16:21:08 [py.warnings] WARNING: G:\Anaconda3-5.0.1\install\lib\site-packages\scrapy\spiders\__init__.py:76: UserWarning: Spider.make_requests_from_ur

l method is deprecated; it won't be called in future Scrapy releases. Please override Spider.start_requests method instead (see httpbintest.spiders.google.Googl

eSpider).

  cls.__module__, cls.__name__

2018-10-11 16:21:09 [scrapy.downloadermiddlewares.retry] DEBUG: Retrying <GET http://www.google.com/> (failed 1 times): Connection was refused by other side: 10

061: 由于目标计算机积极拒绝，无法连接。.

2018-10-11 16:21:10 [scrapy.downloadermiddlewares.retry] DEBUG: Retrying <GET http://www.google.com/> (failed 2 times): Connection was refused by other side: 10

061: 由于目标计算机积极拒绝，无法连接。.

2018-10-11 16:21:11 [scrapy.downloadermiddlewares.retry] DEBUG: Gave up retrying <GET http://www.google.com/> (failed 3 times): Connection was refused by other

side: 10061: 由于目标计算机积极拒绝，无法连接。.

2018-10-11 16:21:12 [scrapy.downloadermiddlewares.retry] DEBUG: Gave up retrying <GET http://www.google.com/> (failed 3 times): Connection was refused by other

side: 10061: 由于目标计算机积极拒绝，无法连接。.

2018-10-11 16:21:13 [scrapy.downloadermiddlewares.retry] DEBUG: Gave up retrying <GET http://www.google.com/> (failed 3 times): Connection was refused by other

side: 10061: 由于目标计算机积极拒绝，无法连接。.

2018-10-11 16:21:14 [scrapy.downloadermiddlewares.retry] DEBUG: Gave up retrying <GET http://www.google.com/> (failed 3 times): Connection was refused by other

side: 10061: 由于目标计算机积极拒绝，无法连接。.

2018-10-11 16:21:15 [scrapy.downloadermiddlewares.retry] DEBUG: Gave up retrying <GET http://www.google.com/> (failed 3 times): Connection was refused by other

side: 10061: 由于目标计算机积极拒绝，无法连接。.

2018-10-11 16:21:16 [scrapy.downloadermiddlewares.retry] DEBUG: Gave up retrying <GET http://www.google.com/> (failed 3 times): Connection was refused by other

side: 10061: 由于目标计算机积极拒绝，无法连接。.

2018-10-11 16:21:17 [scrapy.downloadermiddlewares.retry] DEBUG: Gave up retrying <GET http://www.google.com/> (failed 3 times): Connection was refused by other

side: 10061: 由于目标计算机积极拒绝，无法连接。.

2018-10-11 16:21:18 [scrapy.downloadermiddlewares.retry] DEBUG: Gave up retrying <GET http://www.google.com/> (failed 3 times): Connection was refused by other

side: 10061: 由于目标计算机积极拒绝，无法连接。.

2018-10-11 16:21:19 [scrapy.downloadermiddlewares.retry] DEBUG: Gave up retrying <GET http://www.google.com/> (failed 3 times): Connection was refused by other

side: 10061: 由于目标计算机积极拒绝，无法连接。.

2018-10-11 16:21:20 [scrapy.downloadermiddlewares.retry] DEBUG: Gave up retrying <GET http://www.google.com/> (failed 3 times): Connection was refused by other

side: 10061: 由于目标计算机积极拒绝，无法连接。.

2018-10-11 16:21:21 [scrapy.downloadermiddlewares.retry] DEBUG: Gave up retrying <GET http://www.google.com/> (failed 3 times): Connection was refused by other

side: 10061: 由于目标计算机积极拒绝，无法连接。.

2018-10-11 16:21:22 [scrapy.downloadermiddlewares.retry] DEBUG: Gave up retrying <GET http://www.google.com/> (failed 3 times): Connection was refused by other

side: 10061: 由于目标计算机积极拒绝，无法连接。.

2018-10-11 16:21:23 [scrapy.downloadermiddlewares.retry] DEBUG: Gave up retrying <GET http://www.google.com/> (failed 3 times): Connection was refused by other

side: 10061: 由于目标计算机积极拒绝，无法连接。.

2018-10-11 16:21:24 [scrapy.downloadermiddlewares.retry] DEBUG: Gave up retrying <GET http://www.google.com/> (failed 3 times): Connection was refused by other

side: 10061: 由于目标计算机积极拒绝，无法连接。.

2018-10-11 16:21:25 [scrapy.downloadermiddlewares.retry] DEBUG: Gave up retrying <GET http://www.google.com/> (failed 3 times): Connection was refused by other

side: 10061: 由于目标计算机积极拒绝，无法连接。.

2018-10-11 16:21:26 [scrapy.downloadermiddlewares.retry] DEBUG: Gave up retrying <GET http://www.google.com/> (failed 3 times): Connection was refused by other

side: 10061: 由于目标计算机积极拒绝，无法连接。.

2018-10-11 16:21:27 [scrapy.downloadermiddlewares.retry] DEBUG: Gave up retrying <GET http://www.google.com/> (failed 3 times): Connection was refused by other

side: 10061: 由于目标计算机积极拒绝，无法连接。.

2018-10-11 16:21:28 [scrapy.downloadermiddlewares.retry] DEBUG: Gave up retrying <GET http://www.google.com/> (failed 3 times): Connection was refused by other

side: 10061: 由于目标计算机积极拒绝，无法连接。.

2018-10-11 16:21:29 [scrapy.downloadermiddlewares.retry] DEBUG: Gave up retrying <GET http://www.google.com/> (failed 3 times): Connection was refused by other

side: 10061: 由于目标计算机积极拒绝，无法连接。.

2018-10-11 16:21:30 [scrapy.downloadermiddlewares.retry] DEBUG: Gave up retrying <GET http://www.google.com/> (failed 3 times): Connection was refused by other

side: 10061: 由于目标计算机积极拒绝，无法连接。.

2018-10-11 16:21:31 [scrapy.downloadermiddlewares.retry] DEBUG: Gave up retrying <GET http://www.google.com/> (failed 3 times): Connection was refused by other

side: 10061: 由于目标计算机积极拒绝，无法连接。.

2018-10-11 16:21:31 [scrapy.crawler] INFO: Received SIGINT, shutting down gracefully. Send again to force

2018-10-11 16:21:31 [scrapy.core.engine] INFO: Closing spider (shutdown)

2018-10-11 16:21:32 [scrapy.downloadermiddlewares.retry] DEBUG: Gave up retrying <GET http://www.google.com/> (failed 3 times): Connection was refused by other

side: 10061: 由于目标计算机积极拒绝，无法连接。.

2018-10-11 16:21:32 [scrapy.statscollectors] INFO: Dumping Scrapy stats:

{'downloader/exception_count': 24,

 'downloader/exception_type_count/twisted.internet.error.ConnectionRefusedError': 24,

 'downloader/request_bytes': 5112,

 'downloader/request_count': 24,

 'downloader/request_method_count/GET': 24,

 'finish_reason': 'shutdown',

 'finish_time': datetime.datetime(2018, 10, 11, 8, 21, 32, 343622),

 'log_count/DEBUG': 25,

 'log_count/INFO': 8,

 'log_count/WARNING': 1,

 'retry/count': 2,

 'retry/max_reached': 22,

 'retry/reason_count/twisted.internet.error.ConnectionRefusedError': 2,

 'scheduler/dequeued': 24,

 'scheduler/dequeued/memory': 24,

 'scheduler/enqueued': 25,

 'scheduler/enqueued/memory': 25,

 'start_time': datetime.datetime(2018, 10, 11, 8, 21, 8, 197241)}

2018-10-11 16:21:32 [scrapy.core.engine] INFO: Spider closed (shutdown)

为了防止它持续输出错误结果，所以要禁止它重复的提示错误信息，所以在settings.py里添加下面代码：

DOWNLOADER_MIDDLEWARES = {

   'httpbintest.middlewares.ProxyMiddleware': 543,

   'scrapy.downloadermiddlewares.retry.RetryMiddleware':None,

}

重新运行代码，会看到，解决了重复的问题：

2018-10-11 16:40:39 [scrapy.utils.log] INFO: Scrapy 1.5.1 started (bot: httpbintest)

2018-10-11 16:40:39 [scrapy.utils.log] INFO: Versions: lxml 4.1.0.0, libxml2 2.9.4, cssselect 1.0.3, parsel 1.5.0, w3lib 1.19.0, Twisted 18.7.0, Python 3.6.3 |A

naconda custom (64-bit)| (default, Oct 15 2017, 03:27:45) [MSC v.1900 64 bit (AMD64)], pyOpenSSL 17.2.0 (OpenSSL 1.0.2p  14 Aug 2018), cryptography 2.0.3, Platf

orm Windows-7-6.1.7601-SP1

2018-10-11 16:40:39 [scrapy.crawler] INFO: Overridden settings: {'BOT_NAME': 'httpbintest', 'NEWSPIDER_MODULE': 'httpbintest.spiders', 'SPIDER_MODULES': ['httpb

intest.spiders']}

2018-10-11 16:40:39 [scrapy.middleware] INFO: Enabled extensions:

['scrapy.extensions.corestats.CoreStats',

 'scrapy.extensions.telnet.TelnetConsole',

 'scrapy.extensions.logstats.LogStats']

2018-10-11 16:40:39 [scrapy.middleware] INFO: Enabled downloader middlewares:

['scrapy.downloadermiddlewares.httpauth.HttpAuthMiddleware',

 'scrapy.downloadermiddlewares.downloadtimeout.DownloadTimeoutMiddleware',

 'scrapy.downloadermiddlewares.defaultheaders.DefaultHeadersMiddleware',

 'scrapy.downloadermiddlewares.useragent.UserAgentMiddleware',

 'httpbintest.middlewares.ProxyMiddleware',

 'scrapy.downloadermiddlewares.redirect.MetaRefreshMiddleware',

 'scrapy.downloadermiddlewares.httpcompression.HttpCompressionMiddleware',

 'scrapy.downloadermiddlewares.redirect.RedirectMiddleware',

 'scrapy.downloadermiddlewares.cookies.CookiesMiddleware',

 'scrapy.downloadermiddlewares.httpproxy.HttpProxyMiddleware',

 'scrapy.downloadermiddlewares.stats.DownloaderStats']

2018-10-11 16:40:39 [scrapy.middleware] INFO: Enabled spider middlewares:

['scrapy.spidermiddlewares.httperror.HttpErrorMiddleware',

 'scrapy.spidermiddlewares.offsite.OffsiteMiddleware',

 'scrapy.spidermiddlewares.referer.RefererMiddleware',

 'scrapy.spidermiddlewares.urllength.UrlLengthMiddleware',

 'scrapy.spidermiddlewares.depth.DepthMiddleware']

2018-10-11 16:40:39 [scrapy.middleware] INFO: Enabled item pipelines:

[]

2018-10-11 16:40:39 [scrapy.core.engine] INFO: Spider opened

2018-10-11 16:40:39 [scrapy.extensions.logstats] INFO: Crawled 0 pages (at 0 pages/min), scraped 0 items (at 0 items/min)

2018-10-11 16:40:39 [scrapy.extensions.telnet] DEBUG: Telnet console listening on 127.0.0.1:6023

2018-10-11 16:40:39 [py.warnings] WARNING: G:\Anaconda3-5.0.1\install\lib\site-packages\scrapy\spiders\__init__.py:76: UserWarning: Spider.make_requests_from_ur

l method is deprecated; it won't be called in future Scrapy releases. Please override Spider.start_requests method instead (see httpbintest.spiders.google.Googl

eSpider).

  cls.__module__, cls.__name__

2018-10-11 16:40:40 [scrapy.dupefilters] DEBUG: Filtered duplicate request: <GET http://www.google.com/> - no more duplicates will be shown (see DUPEFILTER_DEBU

G to show all duplicates)

2018-10-11 16:40:40 [scrapy.core.engine] INFO: Closing spider (finished)

2018-10-11 16:40:40 [scrapy.statscollectors] INFO: Dumping Scrapy stats:

{'downloader/exception_count': 1,

 'downloader/exception_type_count/twisted.internet.error.ConnectionRefusedError': 1,

 'downloader/request_bytes': 213,

 'downloader/request_count': 1,

 'downloader/request_method_count/GET': 1,

 'dupefilter/filtered': 1,

 'finish_reason': 'finished',

 'finish_time': datetime.datetime(2018, 10, 11, 8, 40, 40, 872314),

 'log_count/DEBUG': 2,

 'log_count/INFO': 7,

 'log_count/WARNING': 1,

 'scheduler/dequeued': 1,

 'scheduler/dequeued/memory': 1,

 'scheduler/enqueued': 1,

 'scheduler/enqueued/memory': 1,

 'start_time': datetime.datetime(2018, 10, 11, 8, 40, 39, 842255)}

2018-10-11 16:40:40 [scrapy.core.engine] INFO: Spider closed (finished)

那么，接下来就是改process_exception，第一次请求五个是不能请求的，所以这个错误会被process_exception捕捉掉，然后敲写self.logger.debug('Get Exception')代表已经出错了

class ProxyMiddleware(object): # 代理中间件

    logger = logging.getLogger(__name__) # 利用这个可以方便进行scrapy 的log输出

    def process_exception(self,request, exception, spider):

        self.logger.debug('Get Exception')

        return request

重新运行下就会看到

2018-10-11 16:45:36 [scrapy.utils.log] INFO: Scrapy 1.5.1 started (bot: httpbintest)

2018-10-11 16:45:36 [scrapy.utils.log] INFO: Versions: lxml 4.1.0.0, libxml2 2.9.4, cssselect 1.0.3, parsel 1.5.0, w3lib 1.19.0, Twisted 18.7.0, Python 3.6.3 |A

naconda custom (64-bit)| (default, Oct 15 2017, 03:27:45) [MSC v.1900 64 bit (AMD64)], pyOpenSSL 17.2.0 (OpenSSL 1.0.2p  14 Aug 2018), cryptography 2.0.3, Platf

orm Windows-7-6.1.7601-SP1

2018-10-11 16:45:36 [scrapy.crawler] INFO: Overridden settings: {'BOT_NAME': 'httpbintest', 'NEWSPIDER_MODULE': 'httpbintest.spiders', 'SPIDER_MODULES': ['httpb

intest.spiders']}

2018-10-11 16:45:36 [scrapy.middleware] INFO: Enabled extensions:

['scrapy.extensions.corestats.CoreStats',

 'scrapy.extensions.telnet.TelnetConsole',

 'scrapy.extensions.logstats.LogStats']

2018-10-11 16:45:36 [scrapy.middleware] INFO: Enabled downloader middlewares:

['scrapy.downloadermiddlewares.httpauth.HttpAuthMiddleware',

 'scrapy.downloadermiddlewares.downloadtimeout.DownloadTimeoutMiddleware',

 'scrapy.downloadermiddlewares.defaultheaders.DefaultHeadersMiddleware',

 'scrapy.downloadermiddlewares.useragent.UserAgentMiddleware',

 'httpbintest.middlewares.ProxyMiddleware',

 'scrapy.downloadermiddlewares.redirect.MetaRefreshMiddleware',

 'scrapy.downloadermiddlewares.httpcompression.HttpCompressionMiddleware',

 'scrapy.downloadermiddlewares.redirect.RedirectMiddleware',

 'scrapy.downloadermiddlewares.cookies.CookiesMiddleware',

 'scrapy.downloadermiddlewares.httpproxy.HttpProxyMiddleware',

 'scrapy.downloadermiddlewares.stats.DownloaderStats']

2018-10-11 16:45:36 [scrapy.middleware] INFO: Enabled spider middlewares:

['scrapy.spidermiddlewares.httperror.HttpErrorMiddleware',

 'scrapy.spidermiddlewares.offsite.OffsiteMiddleware',

 'scrapy.spidermiddlewares.referer.RefererMiddleware',

 'scrapy.spidermiddlewares.urllength.UrlLengthMiddleware',

 'scrapy.spidermiddlewares.depth.DepthMiddleware']

2018-10-11 16:45:36 [scrapy.middleware] INFO: Enabled item pipelines:

[]

2018-10-11 16:45:36 [scrapy.core.engine] INFO: Spider opened

2018-10-11 16:45:36 [scrapy.extensions.logstats] INFO: Crawled 0 pages (at 0 pages/min), scraped 0 items (at 0 items/min)

2018-10-11 16:45:36 [scrapy.extensions.telnet] DEBUG: Telnet console listening on 127.0.0.1:6023

2018-10-11 16:45:36 [py.warnings] WARNING: G:\Anaconda3-5.0.1\install\lib\site-packages\scrapy\spiders\__init__.py:76: UserWarning: Spider.make_requests_from_ur

l method is deprecated; it won't be called in future Scrapy releases. Please override Spider.start_requests method instead (see httpbintest.spiders.google.Googl

eSpider).

  cls.__module__, cls.__name__

2018-10-11 16:45:37 [httpbintest.middlewares] DEBUG: Get Exception

2018-10-11 16:45:37 [scrapy.dupefilters] DEBUG: Filtered duplicate request: <GET http://www.google.com/> - no more duplicates will be shown (see DUPEFILTER_DEBU

G to show all duplicates)

2018-10-11 16:45:37 [scrapy.core.engine] INFO: Closing spider (finished)

2018-10-11 16:45:37 [scrapy.statscollectors] INFO: Dumping Scrapy stats:

{'downloader/exception_count': 1,

 'downloader/exception_type_count/twisted.internet.error.ConnectionRefusedError': 1,

 'downloader/request_bytes': 213,

 'downloader/request_count': 1,

 'downloader/request_method_count/GET': 1,

 'dupefilter/filtered': 1,

 'finish_reason': 'finished',

 'finish_time': datetime.datetime(2018, 10, 11, 8, 45, 37, 546283),

 'log_count/DEBUG': 3,

 'log_count/INFO': 7,

 'log_count/WARNING': 1,

 'scheduler/dequeued': 1,

 'scheduler/dequeued/memory': 1,

 'scheduler/enqueued': 1,

 'scheduler/enqueued/memory': 1,

 'start_time': datetime.datetime(2018, 10, 11, 8, 45, 36, 500223)}

2018-10-11 16:45:37 [scrapy.core.engine] INFO: Spider closed (finished)

仔细看，看到

爬虫--Scrapy之Downloader Middleware-LMLPHP

现在我们在middlewares.py里重新设置代理，看能否请求成功

class ProxyMiddleware(object): # 代理中间件

    logger = logging.getLogger(__name__) # 利用这个可以方便进行scrapy 的log输出

    def process_exception(self,request, exception, spider):

        self.logger.debug('Get Exception')

        request.meta['proxy'] = 'http://211.101.136.86:49784'  # 设置request的代理，如果请求的时候，request会自动加上这个代理

        return request

设置完成之后，return request就会将这个request重新加在图下的请求队列里，就会重新的执行request请求，然后在回调下面的方法里面，然后输出网页的源代码了

爬虫--Scrapy之Downloader Middleware-LMLPHP

设置好之后，我们就运行一下代码，其输出结果如下：

2018-10-11 17:06:05 [scrapy.utils.log] INFO: Scrapy 1.5.1 started (bot: httpbintest)

2018-10-11 17:06:05 [scrapy.utils.log] INFO: Versions: lxml 4.1.0.0, libxml2 2.9.4, cssselect 1.0.3, parsel 1.5.0, w3lib 1.19.0, Twisted 18.7.0, Python 3.6.3 |A

naconda custom (64-bit)| (default, Oct 15 2017, 03:27:45) [MSC v.1900 64 bit (AMD64)], pyOpenSSL 17.2.0 (OpenSSL 1.0.2p  14 Aug 2018), cryptography 2.0.3, Platf

orm Windows-7-6.1.7601-SP1

2018-10-11 17:06:05 [scrapy.crawler] INFO: Overridden settings: {'BOT_NAME': 'httpbintest', 'NEWSPIDER_MODULE': 'httpbintest.spiders', 'SPIDER_MODULES': ['httpb

intest.spiders']}

2018-10-11 17:06:06 [scrapy.middleware] INFO: Enabled extensions:

['scrapy.extensions.corestats.CoreStats',

 'scrapy.extensions.telnet.TelnetConsole',

 'scrapy.extensions.logstats.LogStats']

2018-10-11 17:06:06 [scrapy.middleware] INFO: Enabled downloader middlewares:

['scrapy.downloadermiddlewares.httpauth.HttpAuthMiddleware',

 'scrapy.downloadermiddlewares.downloadtimeout.DownloadTimeoutMiddleware',

 'scrapy.downloadermiddlewares.defaultheaders.DefaultHeadersMiddleware',

 'scrapy.downloadermiddlewares.useragent.UserAgentMiddleware',

 'httpbintest.middlewares.ProxyMiddleware',

 'scrapy.downloadermiddlewares.redirect.MetaRefreshMiddleware',

 'scrapy.downloadermiddlewares.httpcompression.HttpCompressionMiddleware',

 'scrapy.downloadermiddlewares.redirect.RedirectMiddleware',

 'scrapy.downloadermiddlewares.cookies.CookiesMiddleware',

 'scrapy.downloadermiddlewares.httpproxy.HttpProxyMiddleware',

 'scrapy.downloadermiddlewares.stats.DownloaderStats']

2018-10-11 17:06:06 [scrapy.middleware] INFO: Enabled spider middlewares:

['scrapy.spidermiddlewares.httperror.HttpErrorMiddleware',

 'scrapy.spidermiddlewares.offsite.OffsiteMiddleware',

 'scrapy.spidermiddlewares.referer.RefererMiddleware',

 'scrapy.spidermiddlewares.urllength.UrlLengthMiddleware',

 'scrapy.spidermiddlewares.depth.DepthMiddleware']

2018-10-11 17:06:06 [scrapy.middleware] INFO: Enabled item pipelines:

[]

2018-10-11 17:06:06 [scrapy.core.engine] INFO: Spider opened

2018-10-11 17:06:06 [scrapy.extensions.logstats] INFO: Crawled 0 pages (at 0 pages/min), scraped 0 items (at 0 items/min)

2018-10-11 17:06:06 [scrapy.extensions.telnet] DEBUG: Telnet console listening on 127.0.0.1:6023

2018-10-11 17:06:06 [py.warnings] WARNING: G:\Anaconda3-5.0.1\install\lib\site-packages\scrapy\spiders\__init__.py:76: UserWarning: Spider.make_requests_from_ur

l method is deprecated; it won't be called in future Scrapy releases. Please override Spider.start_requests method instead (see httpbintest.spiders.google.Googl

eSpider).

  cls.__module__, cls.__name__

2018-10-11 17:06:07 [httpbintest.middlewares] DEBUG: Get Exception

2018-10-11 17:06:17 [httpbintest.middlewares] DEBUG: Get Exception

2018-10-11 17:06:21 [scrapy.crawler] INFO: Received SIGINT, shutting down gracefully. Send again to force

2018-10-11 17:06:21 [scrapy.core.engine] INFO: Closing spider (shutdown)

2018-10-11 17:06:27 [httpbintest.middlewares] DEBUG: Get Exception

2018-10-11 17:06:27 [scrapy.statscollectors] INFO: Dumping Scrapy stats:

{'downloader/exception_count': 3,

 'downloader/exception_type_count/twisted.internet.error.ConnectionRefusedError': 1,

 'downloader/exception_type_count/twisted.internet.error.TimeoutError': 2,

 'downloader/request_bytes': 639,

 'downloader/request_count': 3,

 'downloader/request_method_count/GET': 3,

 'finish_reason': 'shutdown',

 'finish_time': datetime.datetime(2018, 10, 11, 9, 6, 27, 317766),

 'log_count/DEBUG': 4,

 'log_count/INFO': 8,

 'log_count/WARNING': 1,

 'scheduler/dequeued': 3,

 'scheduler/dequeued/memory': 3,

 'scheduler/enqueued': 4,

 'scheduler/enqueued/memory': 4,

 'start_time': datetime.datetime(2018, 10, 11, 9, 6, 6, 268562)}

2018-10-11 17:06:27 [scrapy.core.engine] INFO: Spider closed (shutdown)

我们在修改下代码：

class GoogleSpider(scrapy.Spider):

    name = 'google'

    allowed_domains = ['www.google.com']

    start_urls = ['http://www.google.com/']

    def make_requests_from_url(self, url):

        self.logger.debug('Try First Time')

        return scrapy.Request(url = url,meta={'download_timeout':10},callback=self.parse,dont_filter=True) # 设置超时时间,dont_filter=True 防止多次请求，进行过滤

    def parse(self, response):

        print(response.text)

class ProxyMiddleware(object): # 代理中间件

    logger = logging.getLogger(__name__) # 利用这个可以方便进行scrapy 的log输出

    def process_exception(self,request, exception, spider):

        self.logger.debug('Get Exception')

        self.logger.debug('Try Second Time')

        request.meta['proxy'] = 'http://60.208.32.201:80'  # 设置request的代理，如果请求的时候，request会自动加上这个代理

        return request

打印后的结果为：

爬虫--Scrapy之Downloader Middleware-LMLPHP

OK，Byby