Class: Polipus::PolipusCrawler

Inherits:
Object
  • Object
show all
Defined in:
lib/polipus.rb

Constant Summary collapse

OPTS = 
{
  # run 4 threads
  :workers => 4,
  # identify self as Polipus/VERSION
  :user_agent => "Polipus - #{Polipus::VERSION} - #{Polipus::HOMEPAGE}",
  # by default, don't limit the depth of the crawl
  :depth_limit => false,
  # number of times HTTP redirects will be followed
  :redirect_limit => 5,
  # storage engine defaults to DevNull 
  :storage => nil,
  # proxy server hostname 
  :proxy_host => nil,
  # proxy server port number
  :proxy_port => false,
  # HTTP read timeout in seconds
  :read_timeout => 30,
  # HTTP open connection timeout in seconds
  :open_timeout => 10,
  # Time to wait for new messages on Redis
  # After this timeout, current crawling session is marked as terminated
  :queue_timeout => 30,
  # An URL tracker instance. default is Bloomfilter based on redis
  :url_tracker => nil,
  # A Redis options {} that will be passed directly to Redis.new
  :redis_options => {},
  # An instance of logger
  :logger => nil,
  # A logger level
  :logger_level => nil,
  # whether the query string should be included in the saved page
  :include_query_string_in_saved_page => true,
  # Max number of items to keep on redis
  :queue_items_limit => 2_000_000,
  # The adapter used to store exceed (queue_items_limit) redis items
  :queue_overflow_adapter => nil,
  # Every x seconds, the main queue is checked for overflowed items
  :queue_overflow_manager_check_time => 60,
  # If true, each page downloaded will increment a counter on redis
  :stats_enabled => false,
  # Cookies strategy
  :cookie_jar => nil,
  :accept_cookies => false,
  # A set of hosts that should be considered parts of the same domain
  # Eg It can be used to follow links with and without 'www' domain
  :domain_aliases => [],
  # Mark a connection as staled after connection_max_hits request
  :connection_max_hits => nil,
  # Page TTL: mark a page as expired after ttl_page seconds
  :ttl_page => nil
}

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(job_name = 'polipus', urls = [], options = {}) {|_self| ... } ⇒ PolipusCrawler

Returns a new instance of PolipusCrawler.

Yields:

  • (_self)

Yield Parameters:



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# File 'lib/polipus.rb', line 91

def initialize(job_name = 'polipus', urls = [], options = {})

  @job_name     = job_name
  @options      = OPTS.merge(options)
  @options[:queue_timeout] = 1 if @options[:queue_timeout] <= 0
  @logger       = @options[:logger]  ||= Logger.new(nil)
  
  unless @logger.class.to_s == "Log4r::Logger"
    @logger.level = @options[:logger_level] ||= Logger::INFO
  end

  @storage      = @options[:storage] ||= Storage.dev_null

  @http_pool    = []
  @workers_pool = []
  @queues_pool  = []
  
  
  @follow_links_like  = []
  @skip_links_like    = []
  @on_page_downloaded = []
  @on_before_save     = []
  @focus_crawl_block  = nil
  @on_crawl_end       = []
  @redis_factory      = nil

  
  @overflow_manager = nil
  @crawler_name = `hostname`.strip + "-#{@job_name}"

  @storage.include_query_string_in_uuid = @options[:include_query_string_in_saved_page]

  @urls = [urls].flatten.map{ |url| URI(url) }
  @urls.each{ |url| url.path = '/' if url.path.empty? }

  @internal_queue = queue_factory

  execute_plugin 'on_initialize'

  yield self if block_given?

end

Instance Attribute Details

#crawler_name ⇒ Object (readonly)

Returns the value of attribute crawler_name.



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# File 'lib/polipus.rb', line 79

def crawler_name
  @crawler_name
end

#job_name ⇒ Object (readonly)

Returns the value of attribute job_name.



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# File 'lib/polipus.rb', line 76

def job_name
  @job_name
end

#logger ⇒ Object (readonly)

Returns the value of attribute logger.



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# File 'lib/polipus.rb', line 77

def logger
  @logger
end

#options ⇒ Object (readonly)

Returns the value of attribute options.



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# File 'lib/polipus.rb', line 78

def options
  @options
end

#storage ⇒ Object (readonly)

Returns the value of attribute storage.



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# File 'lib/polipus.rb', line 75

def storage
  @storage
end

Class Method Details

.crawl(*args, &block) ⇒ Object 



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# File 'lib/polipus.rb', line 134

def self.crawl(*args, &block)
  new(*args, &block).takeover
end

Instance Method Details

#add_url(url) ⇒ Object

Enqueue an url, no matter what



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# File 'lib/polipus.rb', line 317

def add_url url
  page = Page.new(url)
  @internal_queue << page.to_json
end

#focus_crawl(&block) ⇒ Object

A block of code will be executed on every page downloaded. The code is used to extract urls to visit see links_for method



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# File 'lib/polipus.rb', line 282

def focus_crawl(&block)
  @focus_crawl_block = block
  self
end

#follow_links_like(*patterns) ⇒ Object

A pattern or an array of patterns can be passed as argument An url will be discarded if it doesn’t match patterns



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# File 'lib/polipus.rb', line 248

def follow_links_like(*patterns)
  @follow_links_like = @follow_links_like += patterns.uniq.compact
  self
end

#on_before_save(&block) ⇒ Object

A block of code will be executed on every page downloaded before being saved in the registered storage



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# File 'lib/polipus.rb', line 274

def on_before_save(&block)
  @on_before_save << block
  self
end

#on_crawl_end(&block) ⇒ Object 



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# File 'lib/polipus.rb', line 267

def on_crawl_end(&block)
  @on_crawl_end << block
  self
end

#on_page_downloaded(&block) ⇒ Object

A block of code will be executed on every page downloaded The block takes the page as argument



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# File 'lib/polipus.rb', line 262

def on_page_downloaded(&block)
  @on_page_downloaded << block
  self
end

#queue_size ⇒ Object 



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# File 'lib/polipus.rb', line 291

def queue_size
  @internal_queue.size
end

#redis ⇒ Object 



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# File 'lib/polipus.rb', line 312

def redis
  @redis ||= redis_factory_adapter
end

#redis_factory(&block) ⇒ Object 



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# File 'lib/polipus.rb', line 299

def redis_factory(&block)
  @redis_factory = block
  self
end

#redis_options ⇒ Object 



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# File 'lib/polipus.rb', line 287

def redis_options
  @options[:redis_options]
end

#skip_links_like(*patterns) ⇒ Object

A pattern or an array of patterns can be passed as argument An url will be discarded if it matches a pattern



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# File 'lib/polipus.rb', line 255

def skip_links_like(*patterns)
  @skip_links_like = @skip_links_like += patterns.uniq.compact
  self
end

#stats_reset! ⇒ Object 



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# File 'lib/polipus.rb', line 295

def stats_reset!
  ["polipus:#{@job_name}:errors", "polipus:#{@job_name}:pages"].each {|e| redis.del e}
end

#stop!(cler_queue = false) ⇒ Object

Request to Polipus to stop its work (gracefully) cler_queue = true if you want to delete all of the pending urls to visit



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# File 'lib/polipus.rb', line 324

def stop!(cler_queue = false)
  PolipusSignalHandler.terminate
  @internal_queue.clear(true) if cler_queue
end

#takeover ⇒ Object 



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# File 'lib/polipus.rb', line 138

def takeover
  PolipusSignalHandler.enable
  overflow_items_controller if queue_overflow_adapter

  q = queue_factory
  @urls.each do |u|
    page = Page.new(u.to_s, :referer => '')
    page.user_data.p_seeded = true
    q << page.to_json
  end

  return if q.empty?

  execute_plugin 'on_crawl_start'
  @options[:workers].times do |worker_number|
    @workers_pool << Thread.new do
      @logger.debug {"Start worker #{worker_number}"}
      http  = @http_pool[worker_number]   ||= HTTP.new(@options)
      queue = @queues_pool[worker_number] ||= queue_factory
      queue.process(false, @options[:queue_timeout]) do |message|

        next if message.nil?

        execute_plugin 'on_message_received'

        page = Page.from_json message

        unless should_be_visited?(page.url, false)
          @logger.info {"[worker ##{worker_number}] Page (#{page.url.to_s}) is no more welcome."}
          queue.commit
          next
        end

        if page_exists? page
          @logger.info {"[worker ##{worker_number}] Page (#{page.url.to_s}) already stored."}
          queue.commit
          next
        end
        
        url = page.url.to_s
        @logger.debug {"[worker ##{worker_number}] Fetching page: [#{page.url.to_s}] Referer: #{page.referer} Depth: #{page.depth}"}

        execute_plugin 'on_before_download'

        pages = http.fetch_pages(url, page.referer, page.depth)
        if pages.count > 1
          rurls = pages.map { |e| e.url.to_s }.join(' --> ')
          @logger.info {"Got redirects! #{rurls}"}
          page = pages.pop
          page.aliases = pages.collect { |e| e.url }
          if page_exists? page
            @logger.info {"[worker ##{worker_number}] Page (#{page.url.to_s}) already stored."}
            queue.commit
            next
          end
        else
          page = pages.last
        end
        
        # Execute on_before_save blocks
        @on_before_save.each {|e| e.call(page)} unless page.nil?
        execute_plugin 'on_after_download'
        
        @logger.warn {"Page #{page.url} has error: #{page.error}"} if page.error

        incr_error if page.error

        if page && page.storable?
          @storage.add page
        end
        
        if page
          @logger.debug {"[worker ##{worker_number}] Fetched page: [#{page.url.to_s}] Referrer: [#{page.referer}] Depth: [#{page.depth}] Code: [#{page.code}] Response Time: [#{page.response_time}]"}
          @logger.info  {"[worker ##{worker_number}] Page (#{page.url.to_s}) downloaded"}
        end
        
        incr_pages

        # Execute on_page_downloaded blocks
        @on_page_downloaded.each {|e| e.call(page)} unless page.nil?

        if @options[:depth_limit] == false || @options[:depth_limit] > page.depth 
          links_for(page).each do |url_to_visit|
            next unless should_be_visited?(url_to_visit)
            enqueue url_to_visit, page, queue
          end
        else
          @logger.info {"[worker ##{worker_number}] Depth limit reached #{page.depth}"}
        end

        @logger.debug {"[worker ##{worker_number}] Queue size: #{queue.size}"}
        @overflow_manager.perform if @overflow_manager && queue.empty?
        execute_plugin 'on_message_processed'

        if PolipusSignalHandler.terminated?
          @logger.info {"About to exit! Thanks for using Polipus"}
          queue.commit
          break
        end
        true
      end
    end
  end
  @workers_pool.each {|w| w.join}
  @on_crawl_end.each {|e| e.call(self)}
  execute_plugin 'on_crawl_end'
end

#url_tracker ⇒ Object 



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# File 'lib/polipus.rb', line 304

def url_tracker
  @url_tracker ||=
    @options[:url_tracker] ||=
      UrlTracker.bloomfilter(:key_name => "polipus_bf_#{job_name}",
                             :redis => redis_factory_adapter,
                             :driver => 'lua')
end