scrapy/docs/ref/spider-middleware.rst

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Built-in spider middleware reference

This page describes all spider middleware components that come with Scrapy. For information on how to use them and how to write your own spider middleware, see the :ref:`spider middleware usage guide <topics-spider-middleware>`.

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For a list of the components enabled by default (and their orders) see the :setting:`SPIDER_MIDDLEWARES_BASE` setting.

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Available spider middlewares

DepthMiddleware

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.. module:: scrapy.contrib.spidermiddleware.depth

DepthMiddleware is a scrape middleware used for tracking the depth of each Request inside the site being scraped. It can be used to limit the maximum depth to scrape or things like that.

The :class:`DepthMiddleware` can be configured through the following settings (see the settings documentation for more info):

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  • :setting:`DEPTH_LIMIT` - The maximum depth that will be allowed to crawl for any site. If zero, no limit will be imposed.

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  • :setting:`DEPTH_STATS` - Whether to collect depth stats.

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HttpErrorMiddleware

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.. module:: scrapy.contrib.spidermiddleware.httperror

Filter out response outside of a range of valid status codes.

This middleware filters out every response with status outside of the range 200<=status<300. Spiders can add more exceptions using handle_httpstatus_list spider attribute.

OffsiteMiddleware

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.. module:: scrapy.contrib.spidermiddleware.offsite

Filters out Requests for URLs outside the domains covered by the spider.

This middleware filters out every request whose host names doesn't match :attr:`~scrapy.spider.BaseSpider.domain_name`, or the spider :attr:`~scrapy.spider.BaseSpider.domain_name` prefixed by "www.". Spider can add more domains to exclude using :attr:`~scrapy.spider.BaseSpider.extra_domain_names` attribute.

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RequestLimitMiddleware

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.. module:: scrapy.contrib.spidermiddleware.requestlimit

Limits the maximum number of requests in the scheduler for each spider. When a spider tries to schedule more than the allowed amount of requests, the new requests (returned by the spider) will be dropped.

The :class:`RequestLimitMiddleware` can be configured through the following settings (see the settings documentation for more info):

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  • :setting:`REQUESTS_QUEUE_SIZE` - If non zero, it will be used as an upper limit for the amount of requests that can be scheduled per domain. Can be set per spider using requests_queue_size attribute.

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RestrictMiddleware

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.. module:: scrapy.contrib.spidermiddleware.restrict

Restricts crawling to fixed set of particular URLs.

The :class:`RestrictMiddleware` can be configured through the following settings (see the settings documentation for more info):

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UrlFilterMiddleware

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.. module:: scrapy.contrib.spidermiddleware.urlfilter

Canonicalizes URLs to filter out duplicated ones

UrlLengthMiddleware

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.. module:: scrapy.contrib.spidermiddleware.urllength

Filters out requests with URLs longer than URLLENGTH_LIMIT

The :class:`UrlLengthMiddleware` can be configured through the following settings (see the settings documentation for more info):

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  • :setting:`URLLENGTH_LIMIT` - The maximum URL length to allow for crawled URLs.

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