From cd17c829cf0d7a006ab5594d56fe182a0ffc71d6 Mon Sep 17 00:00:00 2001 From: Andrey Rakhmatullin Date: Mon, 23 Aug 2021 19:55:35 +0500 Subject: [PATCH] Revert "Move documentation about avoiding bans into a topic of its own (#4039)" This reverts commit 2d2581c68f35799dc4372a257eaa8dbb5208481d. --- docs/index.rst | 4 - docs/topics/avoiding-bans.rst | 340 ---------------------------------- docs/topics/practices.rst | 34 ++++ 3 files changed, 34 insertions(+), 344 deletions(-) delete mode 100644 docs/topics/avoiding-bans.rst diff --git a/docs/index.rst b/docs/index.rst index 7647b3781..433798aa8 100644 --- a/docs/index.rst +++ b/docs/index.rst @@ -155,7 +155,6 @@ Solving specific problems topics/debug topics/contracts topics/practices - topics/avoiding-bans topics/broad-crawls topics/developer-tools topics/dynamic-content @@ -180,9 +179,6 @@ Solving specific problems :doc:`topics/practices` Get familiar with some Scrapy common practices. -:doc:`topics/avoiding-bans` - Avoid getting banned from websites. - :doc:`topics/broad-crawls` Tune Scrapy for crawling a lot domains in parallel. diff --git a/docs/topics/avoiding-bans.rst b/docs/topics/avoiding-bans.rst deleted file mode 100644 index 59f0da191..000000000 --- a/docs/topics/avoiding-bans.rst +++ /dev/null @@ -1,340 +0,0 @@ -.. _bans: - -============= -Avoiding bans -============= - -This topic covers some of the strategies that you can follow to avoid getting -different or bad responses from a website that you are crawling due to filters -such as regional filters, web browser filters, etc. - -.. _avoiding-crawls: - -Avoiding crawls -=============== - -The best way not to be banned from a website is not to send requests to it in -the first place. - -One way to avoid crawling a website is to find the desired dataset through -other means. For example, you can use Google’s `dataset search engine`_. - -If the target website is the only or best source of the desired information, -and you only need to extract the data on a monthly basis or a lower frequency, -you may be able to crawl a public snapshot of the target website instead. -`Common Crawl`_ is an open repository of web crawl data that you can access -freely. It contains monthly snapshots of a wide variety of websites and, if you -are lucky, your target website will be among them. - -.. _Common Crawl: https://commoncrawl.org/ -.. _dataset search engine: https://datasetsearch.research.google.com/ - - -.. _being-polite: - -Being polite -============ - -To avoid being banned, you should first avoid giving a website reasons to ban -you. - -.. _identifying-yourself: - -Identifying yourself --------------------- - -If your crawling has a noticeable negative impact on a website or you crawl -content that should not be crawled, website administrators will need to do -something. - -Set :setting:`USER_AGENT` to a value that uniquely identifies your spider and -includes contact information, so that website administrators can contact you. - - -.. _following-robotstxt: - -Following robots.txt guidelines -------------------------------- - -Some websites provide a ``robots.txt`` file at their root path (e.g. -``http://example.com/robots.txt``) that describes the guidelines that they wish -bots to follow when crawling their website. - -Before you start writing a spider for a website, read their ``robots.txt`` -file and implement your spider following its guidelines. See the `robots.txt -standard draft`_ or the `robots.txt Google specification`_ for information on -how to read ``robots.txt`` files. - -To ensure that your spider does not crawl pages restricted by ``robots.txt`` -guidelines, set :setting:`ROBOTSTXT_OBEY` to ``True`` to enable the -:class:`~scrapy.downloadermiddlewares.robotstxt.RobotsTxtMiddleware` -middleware. When you do, if your spider attempts to crawl a restricted page, -this middleware aborts that request with the following message:: - - Forbidden by robots.txt - -Also set :setting:`CONCURRENT_REQUESTS_PER_DOMAIN` and -:setting:`DOWNLOAD_DELAY` to values that comply with the ``Crawl-Delay`` or -``Request-Rate`` directives from the ``robots.txt`` guidelines. - -You may also use the :ref:`AutoThrottle extension ` on top -of that, so that when the target website experiences a high load, your spider -automatically switches to higher download delays. - -.. _robots.txt Google specification: https://developers.google.com/search/reference/robots_txt -.. _robots.txt standard draft: https://tools.ietf.org/html/draft-koster-rep-00 - - -.. _choosing-crawl-speed: - -Finding the right guidelines on your own ----------------------------------------- - -If a website does not specify a desired download delay, or does not provide a -``robots.txt`` file, you should make an effort to find out the right values for -:setting:`CONCURRENT_REQUESTS_PER_DOMAIN` and :setting:`DOWNLOAD_DELAY` that -will not have a noticeable negative impact on the target website. - -Use a service like `SimilarWeb`_ to find out the amount of monthly traffic that -the target website receives, and choose concurrency and delay values that will -not cause a noticeable traffic increase. - -.. _SimilarWeb: https://www.similarweb.com - - -.. _filters-and-challenges: - -Bypassing filters and solving challenges -======================================== - -Some websites implement filters and challenges that aim to deny access or alter -their content based on aspects of the visitor, such as the country where they -are or the web browsing tool they use. - -.. _regional-filter: - -Bypassing regional filters --------------------------- - -Some websites send different or bad responses based on the region or country -associated to your `IP address`_. - -To bypass these filters, get access to a `proxy server`_ that has an outgoing -IP address from a region that gets the desired responses. - -Use the :class:`~scrapy.downloadermiddlewares.httpproxy.HttpProxyMiddleware` -middleware to configure your spider to use that proxy. - -.. _IP address: https://en.wikipedia.org/wiki/IP_address -.. _proxy server: https://en.wikipedia.org/wiki/Proxy_server - - -.. _web-browser-filter: - -Bypassing web browser filters ------------------------------ - -Some websites send different or bad responses if they detect that your request -does not come from a web browser. - -To bypass these filters, switch your :setting:`USER_AGENT` to a value copied -from those that popular web browsers use. In some rare cases, you may need a -user agent string from a specific web browser. - -There are multiple Scrapy plugins that can rotate your requests through popular -web browser user agent strings, such as scrapy-fake-useragent_, -scrapy-random-useragent_ or Scrapy-UserAgents_. - -For advanced web browser filters, -:ref:`pre-rendering JavaScript ` or -:ref:`using a headless browser ` may be necessary. -Use these options only as a last resort, however, because they cause a higher -load per request on the target website. - -.. _scrapy-fake-useragent: https://github.com/alecxe/scrapy-fake-useragent -.. _scrapy-random-useragent: https://github.com/cleocn/scrapy-random-useragent -.. _Scrapy-UserAgents: https://pypi.org/project/Scrapy-UserAgents/ - - -.. _request-delay-filter: - -Bypassing request delay filters -------------------------------- - -Some websites may ban your IP after they detect that your requests use a -constant download delay. - -To help bypassing these filters, the :setting:`RANDOMIZE_DOWNLOAD_DELAY` -setting is enabled by default. When that is not enough, an -:ref:`IP address rotation solution ` may be much more effective. - - -.. _isp-filter: - -Bypassing internet service provider filters -------------------------------------------- - -Some websites send different or bad responses if they detect that your request -comes from an IP address that belongs to a `data center`_, as opposed to a -residential IP address from an `internet service provider`_ or a mobile IP -address from a `mobile network`_. - -To bypass these filters, get access to a proxy server that has an outgoing IP -address that is either residential or mobile. Note that you may also get -different responses depending on whether your IP address is residential or -mobile. - -Use the :class:`~scrapy.downloadermiddlewares.httpproxy.HttpProxyMiddleware` -middleware to configure your spider to use that proxy. - -.. _data center: https://en.wikipedia.org/wiki/Data_center -.. _internet service provider: https://en.wikipedia.org/wiki/Internet_service_provider -.. _mobile network: https://en.wikipedia.org/wiki/Cellular_network - - -.. _captcha: - -Solving CAPTCHA challenges --------------------------- - -Some websites require you to solve a `CAPTCHA challenge`_ to get the desired -response. - -To bypass these filters, several options exist: - -- You could have your spider present the CAPTCHA challenge to you and wait - for you to solve it manually. - -- Some CAPTCHA challenges can be solved using an `optical character - recognition`_ (OCR) solution such as pytesseract_. - -- Paid CAPTCHA solving services exist. - -Whichever solution you choose, implement it as a :ref:`downloader middleware -` that automatically detects CAPTCHA challenges -in responses and solves them, so that your spider code only receives successful -responses. - -.. _CAPTCHA challenge: https://en.wikipedia.org/wiki/CAPTCHA -.. _optical character recognition: https://en.wikipedia.org/wiki/Optical_character_recognition -.. _pytesseract: https://github.com/madmaze/pytesseract - - -.. _ip-rotation: - -IP address rotation solutions -============================= - -See below some of the different solutions there are to have your requests use -different outgoing IP addresses. - -When using this approach, remember to set :setting:`COOKIES_ENABLED` to -``False`` to disable global cookie handling. This prevents websites from -identifying two requests as coming from the same user agent even if they come -from different IP addresses and have different user-agent strings. You can -still include some cookies manually in your requests. Define them through the -``Cookies`` header of your requests. See -:class:`Request.headers `. - -.. _smart-proxy: - -Smart proxies -------------- - -An increasing number of websites use solutions that apply many of the above -filters and challenges at the same time. - -There are paid proxy services, like `Zyte Smart Proxy Manager`_, that -automatically bypass website filters and challenges, so that your spider only -gets successful responses. They also allow managing sessions to simulate user -behavior. - -For Zyte Smart Proxy Manager, installing scrapy-crawlera_ will offer advanced -integration with Scrapy. For other services, use the -:class:`~scrapy.downloadermiddlewares.httpproxy.HttpProxyMiddleware` middleware -or implement your own :ref:`downloader middleware -`. - -.. _scrapy-crawlera: https://scrapy-crawlera.readthedocs.io/en/latest/ -.. _Zyte Smart Proxy Manager: https://www.zyte.com/smart-proxy-manager/ - - -.. _rotating-proxy: - -Rotating proxies ----------------- - -Rotating proxy services like ProxyMesh_ send different requests through -different proxies. This can decrease the likelihood of being affected by some -filters or challenges. - -.. _ProxyMesh: https://proxymesh.com/ - - -.. _free-proxies: - -Free proxies ------------- - -You can easily find lists of free proxies in the internet, and you can use -a solution like `scrapy-rotating-proxies`_ to configure multiple proxies in -your spider and have requests rotate through them automatically. - -This approach, however, has serious drawbacks: - -- Free proxies may stop working at any moment. You need to implement a way to - refresh your list of free proxies. - -- In addition to handling occasional bad responses from websites, you - need to handle all kinds of bad responses from proxies. You may even need - to inspect the response body to determine if a response comes from the - target website or from a misbehaving proxy. - -- Advanced antibot solutions may automatically detect and filter out traffic - from free proxies. - -.. _scrapy-rotating-proxies: https://github.com/TeamHG-Memex/scrapy-rotating-proxies - - -.. _custom-rotating-proxy: - -Custom rotating proxy ---------------------- - -If you have spare servers, you can set them up as proxies and use scrapoxy_ to -build a custom proxy that rotates traffic through them. However, the initial -setup can be complex, and your requests will be vulnerable to -:ref:`internet service provider filtering `. - -.. _scrapoxy: https://scrapoxy.io/ - - -.. _tor: - -The Tor network ---------------- - -It is possible to send requests through the `Tor network`_. - -The initial setup to have Scrapy working with Tor is not straightforward. -Use a search engine to find up-to-date documentation specific to using -Scrapy and Tor together. - -The main drawback of using the Tor network is that traffic can be extremely -slow. - -.. _Tor network: https://en.wikipedia.org/wiki/Tor_(anonymity_network) - - -.. _commercial-support: - -Seeking professional help -========================= - -Avoiding bans, filters and challenges can be difficult and tricky, and may -sometimes require special infrastructure. - -If you find yourself unable to prevent your spider from getting bad responses, -consider contacting `commercial support`_. - -.. _commercial support: https://scrapy.org/support/ diff --git a/docs/topics/practices.rst b/docs/topics/practices.rst index a7a6fd129..732eba587 100644 --- a/docs/topics/practices.rst +++ b/docs/topics/practices.rst @@ -226,5 +226,39 @@ crawl:: curl http://scrapy2.mycompany.com:6800/schedule.json -d project=myproject -d spider=spider1 -d part=2 curl http://scrapy3.mycompany.com:6800/schedule.json -d project=myproject -d spider=spider1 -d part=3 +.. _bans: +Avoiding getting banned +======================= + +Some websites implement certain measures to prevent bots from crawling them, +with varying degrees of sophistication. Getting around those measures can be +difficult and tricky, and may sometimes require special infrastructure. Please +consider contacting `commercial support`_ if in doubt. + +Here are some tips to keep in mind when dealing with these kinds of sites: + +* rotate your user agent from a pool of well-known ones from browsers (google + around to get a list of them) +* disable cookies (see :setting:`COOKIES_ENABLED`) as some sites may use + cookies to spot bot behaviour +* use download delays (2 or higher). See :setting:`DOWNLOAD_DELAY` setting. +* if possible, use `Google cache`_ to fetch pages, instead of hitting the sites + directly +* use a pool of rotating IPs. For example, the free `Tor project`_ or paid + services like `ProxyMesh`_. An open source alternative is `scrapoxy`_, a + super proxy that you can attach your own proxies to. +* use a highly distributed downloader that circumvents bans internally, so you + can just focus on parsing clean pages. One example of such downloaders is + `Zyte Smart Proxy Manager`_ + +If you are still unable to prevent your bot getting banned, consider contacting +`commercial support`_. + +.. _Tor project: https://www.torproject.org/ +.. _commercial support: https://scrapy.org/support/ +.. _ProxyMesh: https://proxymesh.com/ +.. _Google cache: http://www.googleguide.com/cached_pages.html .. _testspiders: https://github.com/scrapinghub/testspiders +.. _scrapoxy: https://scrapoxy.io/ +.. _Zyte Smart Proxy Manager: https://www.zyte.com/smart-proxy-manager/