metainspector

MetaInspector

MetaInspector is a gem for web scraping purposes.

You give it an URL, and it lets you easily get its title, links, images, charset, description, keywords, meta tags...

Installation

Install the gem from RubyGems:

gem install metainspector

If you're using it on a Rails application, just add it to your Gemfile and run bundle install

gem 'metainspector'

Supported Ruby versions are defined in .circleci/config.yml.

Supporting MetaInspector

MetaInspector has been downloaded more than 3 million times via RubyGems.org and has more than 1K stars on Github.

If you're using MetaInspector, it would be much appreciated if you can give back to the project in order to help ensure its continued development.

Gold Sponsors

Silver Sponsors

Bronze Sponsors

Usage

Initialize a MetaInspector instance for an URL, like this:

page = MetaInspector.new('https://github.com')

If you don't include the scheme on the URL, http:// will be used by default:

page = MetaInspector.new('github.com')

You can also include the html which will be used as the document to scrape:

page = MetaInspector.new("https://github.com",
                         :document => "...")

Accessing response

You can check the status and headers from the response like this:

page.response.status  # 200
page.response.headers # { "server"=>"nginx", "content-type"=>"text/html; charset=utf-8",
                      #   "cache-control"=>"must-revalidate, private, max-age=0", ... }

Accessing scraped data

URL

page.url                 # URL of the page
page.tracked?            # returns true if the url contains known tracking parameters
page.untracked_url       # returns the url with the known tracking parameters removed
page.untrack!            # removes the known tracking parameters from the url
page.scheme              # Scheme of the page (http, https)
page.host                # Hostname of the page (like, github.com, without the scheme)
page.root_url            # Root url (scheme + host, like https://github.com/)

Head links

page.head_links          # an array of hashes of all head/links
page.stylesheets         # an array of hashes of all head/links where rel='stylesheet'
page.canonicals          # an array of hashes of all head/links where rel='canonical'
page.feeds               # Get rss or atom links in meta data fields as array of hash in the form { href: "...", title: "...", type: "..." }

Texts

…

Links

page.links.raw           # every link found, unprocessed
page.links.all           # every link found on the page as an absolute URL
page.links.http          # every HTTP link found
page.links.non_http      # every non-HTTP link found
page.links.internal      # every internal link found on the page as an absolute URL
page.links.external      # every external link found on the page as an absolute URL

Images

page.images              # enumerable collection, with every img found on the page as an absolute URL
page.images.with_size    # a sorted array (by descending area) of [image_url, width, height]
page.images.best         # Most relevant image, if defined with the og:image or twitter:image metatags. Fallback to the first page.images array element
page.images.favicon      # absolute URL to the favicon

Meta tags

When it comes to meta tags, you have several options:

…

As this method returns a hash, you can also take only the key that you need, like in:

…

In most cases you will only be interested in the first occurrence of a meta tag, so you can use the singular form of that method:

page.meta_tag['name']   # Returns:
                        # {
                        #   'keywords'       => 'one, two, three',
                        #   'description'    => 'the description',
                        #   'author'         => 'Joe Sample',
                        #   'robots'         => 'index,follow',
                        #   'revisit'        => '15 days',
                        #   'dc.date.issued' => '2011-09-15'
                        # }

Or, as this is also a hash:

page.meta_tag['name']['keywords']    # Returns 'one, two, three'

And finally, you can use the shorter meta method that will merge the different keys so you have a simpler hash:

…

This way, you can get most meta tags just like that:

page.meta['author']     # Returns "Joe Sample"

Please be aware that all keys are converted to downcase, so it's 'dc.date.issued' and not 'DC.date.issued'.

Misc

page.charset             # UTF-8
page.content_type        # content-type returned by the server when the url was requested

Other representations

You can also access most of the scraped data as a hash:

page.to_hash    # { "url"   => "https://github.com",
                    "title" => "GitHub", ... }

The original document is accessible from:

page.to_s         # A String with the contents of the HTML document

And the full scraped document is accessible from:

page.parsed  # Nokogiri doc that you can use it to get any element from the page

Options

Forced encoding

If you get a MetaInspector::RequestError, "invalid byte sequence in UTF-8" or similar error, you can try forcing the encoding like this:

page = MetaInspector.new(url, :encoding => 'UTF-8')

Timeout & Retries

You can specify 2 different timeouts when requesting a page:

• connection_timeout sets the maximum number of seconds to wait to get a connection to the page.
• read_timeout sets the maximum number of seconds to wait to read the page, once connected.

Both timeouts default to 20 seconds each.

You can also specify the number of retries, which defaults to 3.

For example, this will time out after 10 seconds waiting for a connection, or after 5 seconds waiting to read its contents, and will retry 4 times:

page = MetaInspector.new('www.google', :connection_timeout => 10, :read_timeout => 5, :retries => 4)

If MetaInspector fails to fetch the page after it has exhausted its retries, it will raise MetaInspector::TimeoutError, which you can rescue in your application code.

begin
  page = MetaInspector.new(url)
rescue MetaInspector::TimeoutError
  enqueue_for_future_fetch_attempt(url)
  render_simple(url)
else
  render_rich(page)
end

Redirections

By default, MetaInspector will follow redirects (up to a limit of 10).

If you want to disallow redirects, you can do it like this:

page = MetaInspector.new('facebook.com', :allow_redirections => false)

You can also customize how many redirects you wish to allow:

page = MetaInspector.new('facebook.com', :faraday_options => { redirect: { limit: 5 } })

And even customize what to do in between each redirect:

callback = proc do |previous_response, next_request|
  ip_address = Resolv.getaddress(next_request.url.host)
  raise 'Invalid address' if IPAddr.new(ip_address).private?
end

page = MetaInspector.new(url, faraday_options: { redirect: { callback: callback } })

The faraday_options[:redirect] hash is passed to the FollowRedirects middleware used by Faraday, so that we can use all available options. Check them here.

Headers

By default, the following headers are set:

{
  'User-Agent'      => "MetaInspector/#{MetaInspector::VERSION} (+https://github.com/jaimeiniesta/metainspector)",
  'Accept-Encoding' => 'identity'
}

The Accept-Encoding is set to identity to avoid exceptions being raised on servers that return malformed compressed responses, as explained here.

If you want to override the default headers then use the headers option:

# Set the User-Agent header
page = MetaInspector.new('example.com', :headers => {'User-Agent' => 'My custom User-Agent'})

Disabling SSL verification (or any other Faraday options)

Faraday can be passed options via :faraday_options.

This is useful in cases where we need to customize the way we request the page, like for example disabling SSL verification, like this:

MetaInspector.new('https://example.com')
# Faraday::SSLError: SSL_connect returned=1 errno=0 state=SSLv3 read server certificate B: certificate verify failed

MetaInspector.new('https://example.com', faraday_options: { ssl: { verify: false } })
# Now we can access the page

Allow non-HTML content type

MetaInspector will by default raise an exception when trying to parse a non-HTML URL (one that has a content-type different than text/html). You can disable this behaviour with:

page = MetaInspector.new('github.com', :allow_non_html_content => true)

page = MetaInspector.new('http://example.com/image.png')
page.content_type  # "image/png"
page.description   # will raise an exception

page = MetaInspector.new('http://example.com/image.png', :allow_non_html_content => true)
page.content_type  # "image/png"
page.description   # will return a garbled string

URL Normalization

By default, URLs are normalized using the Addressable gem. For example:

# Normalization will add a default scheme and a trailing slash...
page = MetaInspector.new('github.com')
page.url # https://github.com/

# ...and it will also convert international characters
page = MetaInspector.new('http://www.詹姆斯.com')
page.url # http://www.xn--8ws00zhy3a.com/

While this is generally useful, it can be tricky sometimes.

You can disable URL normalization by passing the normalize_url: false option.

Image downloading

When you ask for the largest image on the page with page.images.largest, it will be determined by its height and width attributes on the HTML markup, and also by downloading a small portion of each image using the fastimage gem. This is really fast as it doesn't download the entire images, normally just the headers of the image files.

If you want to disable this, you can specify it like this:

page = MetaInspector.new('http://example.com', download_images: false)

Caching responses

MetaInspector can be configured to use Faraday::HttpCache to cache page responses. For that you should pass the faraday_http_cache option with at least the :store key, for example:

cache = ActiveSupport::Cache.lookup_store(:file_store, '/tmp/cache')
page = MetaInspector.new('http://example.com', faraday_http_cache: { store: cache })

Exception Handling

Web page scraping is tricky, you can expect to find different exceptions during the request of the page or the parsing of its contents. MetaInspector will encapsulate these exceptions on these main errors:

• MetaInspector::TimeoutError. When fetching a web page has taken too long.
• MetaInspector::RequestError. When there has been an error on the request phase. Examples: page not found, SSL failure, invalid URI.
• MetaInspector::ParserError. When there has been an error parsing the contents of the page.
• MetaInspector::NonHtmlError. When the contents of the page was not HTML. See also the allow_non_html_content option

Examples

You can find some sample scripts on the examples folder, including a basic scraping and a spider that will follow external links using a queue. What follows is an example of use from