Web scrape troubleshooting: Difference between revisions

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# The web page needed to signed in
# The web page needed to signed in
# Blocking the request without {{kbd | key= Referer}} or other headers.
# Blocking the request without {{kbd | key= Referer}} or other headers.
# Connection timeout during a http request. e.g. In PHP {{kbd | key=default_socket_timeout}} is 30 seconds<ref>[https://www.php.net/manual/en/filesystem.configuration.php PHP: Runtime Configuration - Manual]</ref><ref>[https://curl.haxx.se/libcurl/c/libcurl-errors.html libcurl - Error Codes]</ref>.
# Connection timeout during a http request. e.g. In PHP {{kbd | key=default_socket_timeout}} is 30 seconds<ref>[https://www.php.net/manual/en/filesystem.configuration.php PHP: Runtime Configuration - Manual]</ref><ref>[https://curl.haxx.se/libcurl/c/libcurl-errors.html libcurl - Error Codes]</ref>.
# Language and [http://php.net/manual/en/function.urlencode.php URL-encodes string]
# Language and [http://php.net/manual/en/function.urlencode.php URL-encodes string]
# [[Extract article text from web page]]
# [[Extract article text from web page]]
# [[Data cleaning#Data_handling | Data cleaning]] issues e.g. [https://en.wikipedia.org/wiki/Non-breaking_space Non-breaking space] or other [https://en.wikipedia.org/wiki/Whitespace_character Whitespace character]
# [[Data cleaning#Data_handling | Data cleaning]] issues e.g. [https://en.wikipedia.org/wiki/Non-breaking_space Non-breaking space] or other [https://en.wikipedia.org/wiki/Whitespace_character Whitespace character]
# Is link a permanent link?
# Enable/Disable the CSS or JavaScript
# Enable/Disable the CSS or JavaScript


Revision as of 18:39, 27 May 2022

Before start to writing the scirpt of web scraping (crawler)

  • Is the website offer datasets or files? e.g. open data
  • Is the website offer API (Application programming interface)?


List of technical issues

  1. Content of web page was changed (revision): The expected web content (of specified DOM element) became empty.
    • Multiple sources of same column such as different HTML DOM but have the same column value.
    • Backup the HTML text of parent DOM element
    • (optional) Complete HTML file backup
  2. The IP was banned from server
  3. CAPTCHA
  4. AJAX
  1. The web page needed to signed in
  1. Blocking the request without Referer or other headers.
  1. Connection timeout during a http request. e.g. In PHP default_socket_timeout is 30 seconds[1][2].
  1. Language and URL-encodes string
  1. Extract article text from web page
  1. Data cleaning issues e.g. Non-breaking space or other Whitespace character
  1. Is link a permanent link?
  1. Enable/Disable the CSS or JavaScript
Difficulty in implementing Descriptioin Approach Comments
Easy Well-formatted HTML elements Url is the resource of dataset.
Advanced Interactive websites Url is the resource of dataset. Require to simulate post form submit with the form data or user agent Using HTTP request and response data tool or PHP: cURL
more difficult Interactive websites Require to simulate the user behavior on browser such as click the button, submit the form and obtain the file finally. Using Selenium or Headless Chrome
Difficult Interactive websites Ajax


Search keyword strategy

How to find the unofficial (3rd-party) web crawler? Search keyword strategy suggested as follows:

  • target website + crawler site:github.com
  • target website + scraper site:github.com
  • target website + bot site:github.com
  • target website + download / downloader site:github.com
  • target website + browser client site:github.com

Further reading

References

  1. ↑ PHP: Runtime Configuration - Manual
  2. ↑ libcurl - Error Codes


Troubleshooting of ...

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