Class: Scrappy::Agent

Inherits:
Object
  • Object
show all
Includes:
MapReduce, MonitorMixin, BlindAgent, Cached, Extractor, Optimizer, Trainer
Defined in:
lib/scrappy/agent/agent.rb

Constant Summary collapse

Options = 
OpenStruct.new :format=>:yarf, :format_header=>true, :depth=>0, :delay=>0, :workers=>10
ContentTypes = 
{ :png => 'image/png', :rdfxml => 'application/rdf+xml',
:rdf => 'application/rdf+xml' }

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Methods included from BlindAgent

#html, #html_data?, #uri, #uri=

Methods included from Cached

#cache, included

Methods included from MapReduce

#cluster, #process, #work

Methods included from Optimizer

#optimize_patterns

Methods included from Trainer

#train

Methods included from Extractor

#extract, #fragments_for

Constructor Details

#initialize(args = {}) ⇒ Agent

Returns a new instance of Agent.



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# File 'lib/scrappy/agent/agent.rb', line 24

def initialize args={}
  super()
  @cluster_count   = args[:workers] || Options.workers
  @cluster_options = [ { :referenceable=>Options.referenceable, :agent=>Options.agent,
                         :workers=>1, :window=>false } ]
  @cluster = args[:parent]
  @id = args[:id] || Agent.pool.keys.size
  Agent.pool[@id] = self
  @kb = args[:kb] || Options.kb
  @options = Options.clone
  @repository = args[:repository] || Options.repository
end

Instance Attribute Details

#id ⇒ Object

Returns the value of attribute id.



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# File 'lib/scrappy/agent/agent.rb', line 22

def id
  @id
end

#kb ⇒ Object

Returns the value of attribute kb.



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# File 'lib/scrappy/agent/agent.rb', line 22

def kb
  @kb
end

#options ⇒ Object

Returns the value of attribute options.



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# File 'lib/scrappy/agent/agent.rb', line 22

def options
  @options
end

Class Method Details

.[](id) ⇒ Object 



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# File 'lib/scrappy/agent/agent.rb', line 18

def self.[] id
  pool[id] || Agent.new(:id=>id)
end

.pool ⇒ Object 



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# File 'lib/scrappy/agent/agent.rb', line 15

def self.pool
  @pool ||= {}
end

Instance Method Details

#map(args, queue = nil) ⇒ Object 



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# File 'lib/scrappy/agent/agent.rb', line 37

def map args, queue=nil
  depth = args[:depth] || options.depth
  request = { :method=>args[:method]||:get, :uri=>complete_uri(args[:uri]), :inputs=>args[:inputs]||{} }

  # Expire cache
  cache.expire! 300 # 5 minutes

  # Lookup in cache
  triples = if cache[request]
    puts "Retrieving cached #{request[:uri]}...done!" if options.debug
    
    cache[request][:response]
  elsif @repository
    # Extracts from the repository 
    request_from_repository(request)
  else
    # Perform the request
    request_uncached(request)
  end

  # If previous cache exists, do not cache it again
  unless cache[request]
    # Cache the request
    cache[request]                       = { :time=>Time.now, :response=>triples }
    cache[request.merge(:uri=>self.uri)] = { :time=>Time.now, :response=>triples } if self.uri
  end

  # Enqueue subresources
  # Pages are enqueued without reducing depth
  pages = triples.select { |s,p,o| p==ID("rdf:type") and o==ID("sc:Page") }.map{|s,p,o| s}.select{|n| n.is_a?(Symbol)}

  # All other URIS are enqueued with depth reduced
  uris = if depth != 0
    (triples.map { |s, p, o| [s,o] }.flatten - [ID(self.uri)] - pages).select{|n| n.is_a?(Symbol)}
  else
    []
  end

  # Recently created URIs are not followed
  nofollow = triples.select { |s,p,o| p==ID("rdf:type") and o==ID("sc:NewUri") }.map{|s,p,o| s}.select{|n| n.is_a?(Symbol)}
  pages -= nofollow
  uris  -= nofollow
  
  items = ( pages.map { |uri| {:uri=>uri.to_s, :depth=>[-1, depth].max} } +
            uris.map  { |uri| {:uri=>uri.to_s, :depth=>[-1, depth-1].max} } ).
            uniq.select { |item| !RDF::ID.bnode?(item[:uri]) }
  
  items.each { |item| puts "Enqueuing (depth = #{item[:depth]}): #{item[:uri]}" if !queue or !(queue.history + queue.items).include?(item) } if options.debug
  
  if queue
    items.each { |item| queue.push_unless_done item }
  else
    triples += process items
  end

  triples unless options.dump
end

#observe(uris) ⇒ Object

Method to observe several webs, and extract the data periodically



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# File 'lib/scrappy/agent/agent.rb', line 140

def observe uris
  while true
    time_init = Time.now.to_i
    uris.each do |uri|
      puts "Pinging #{uri}..."
      request :uri=>uri
    end
    time = options.repository.time * 60 - (Time.now.to_i - time_init)
    puts "Sleeping until #{Time.now + time}..."
    sleep time
  end
end

#proxy(args = {}) ⇒ Object 



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# File 'lib/scrappy/agent/agent.rb', line 114

def proxy args={}
  request  = { :method=>:get, :inputs=>{}, :format=>options.format, :depth=>options.depth }.merge(args)
  
  response = self.request(request)
  
  output = if options.dump
    ""
  else
    if options.debug
      print "Serializing..."; $stdout.flush
    end
    
    output = response.serialize request[:format], options.format_header
  
    puts 'done!'if options.debug
    
    output
  end

  OpenStruct.new :output => output,
                 :content_type => ContentTypes[request[:format]] || 'text/plain',
                 :uri => self.uri,
                 :status => self.html_data? ? (self.uri == request[:uri] ? :ok : :redirect) : :error
end

#reduce(results) ⇒ Object 



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# File 'lib/scrappy/agent/agent.rb', line 95

def reduce results
  return [] if options.dump
  
  if options.debug
    print "Merging results..."; $stdout.flush
  end
  
  triples = []; results.each { |result| triples += result }
  triples.uniq!
  
  puts 'done!'if options.debug
  
  triples
end

#request(args = {}) ⇒ Object 



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# File 'lib/scrappy/agent/agent.rb', line 110

def request args={}
  RDF::Graph.new clean(map(args) || [])
end