Class: Pluto::Fetcher

Inherits:
Object
  • Object
show all
Includes:
LogUtils::Logging
Defined in:
lib/pluto/fetcher.rb

Instance Method Summary collapse

Constructor Details

#initialize ⇒ Fetcher

Returns a new instance of Fetcher.



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# File 'lib/pluto/fetcher.rb', line 8

def initialize
  @worker  = ::Fetcher::Worker.new
end

Instance Method Details

#debug=(value) ⇒ Object 



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# File 'lib/pluto/fetcher.rb', line 12

def debug=(value)  @debug = value;   end

#debug? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/pluto/fetcher.rb', line 13

def debug?()       @debug || false;  end

#feed_by_rec(feed_rec) ⇒ Object 



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# File 'lib/pluto/fetcher.rb', line 48

def feed_by_rec( feed_rec )
  # simple feed fetcher; use for debugging (only/mostly)
  #  -- will NOT change db records in any way

  feed_url = feed_rec.feed_url
  feed_key = feed_rec.key

  feed_xml = fetch_feed( feed_url )

  logger.debug "feed_xml:"
  logger.debug feed_xml[ 0..500 ] # get first 500 chars

  #  if opts.verbose?  # also write a copy to disk
  if debug?
    logger.debug "saving feed to >./#{feed_key}.xml<..."
    File.open( "./#{feed_key}.xml", 'w' ) do |f|
      f.write( feed_xml )
    end
  end
    
  puts "Before parsing feed >#{feed_key}<..."

  ## fix/todo: check for feed.nil?   -> error parsing!!!
  #    or throw exception
  feed = FeedUtils::Parser.parse( feed_xml )
end

#feed_by_rec_if_modified(feed_rec) ⇒ Object

try smart http update; will update db records



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# File 'lib/pluto/fetcher.rb', line 76

def feed_by_rec_if_modified( feed_rec )   # try smart http update; will update db records
  feed_url = feed_rec.feed_url
  feed_key = feed_rec.key

  ### todo/fix:
  ##  add if available http_etag  machinery for smarter updates
  ##    and http_last_modified headers
  ##    and brute force body_old == body_new   etc.

  ### todo/fix: normalize/unifiy feed_url
  ##  - same in fetcher - use shared utitlity method or similar

  @worker.use_cache = true
  @worker.cache[ feed_url ] = {
    'etag'          => feed_rec.http_etag,
    'last-modified' => feed_rec.http_last_modified
  }

  ### fix bug in fetcher - do NOT use request_uri use uri.to
  ## - add request_uri entry to (e.g. w/o host etc.)
  ## - remove code here once fixed in fetcher
  @worker.cache[ URI.parse( feed_url ).request_uri ] = {
    'etag'          => feed_rec.http_etag,
    'last-modified' => feed_rec.http_last_modified
  }


  response = @worker.get( feed_url )
  @worker.use_cache = false   # fix/todo: restore old use_cache setting instead of false

  if response.code == '304'  # not modified (conditional GET - e.g. using etag/last-modified)
    puts "OK - fetching feed '#{feed_key}' - HTTP status #{response.code} #{response.message}"
    puts "no change; request returns not modified (304); skipping parsing feed"
    return nil   # no updates available; nothing to do
  end

  feed_fetched = Time.now

  if response.code != '200'   # note Net::HTTP response.code is a string in ruby

    puts "*** error: fetching feed '#{feed_key}' - HTTP status #{response.code} #{response.message}"
    
    feed_attribs = {
      http_code:          response.code.to_i,
      http_server:        response.header[ 'server' ],
      http_etag:          nil,
      http_last_modified: nil,
      body:               nil,
      md5:                nil,
      fetched:            feed_fetched 
    }
    feed_rec.update_attributes!( feed_attribs )
    return nil  #  sorry; no feed for parsing available
  end

  puts "OK - fetching feed '#{feed_key}' - HTTP status #{response.code} #{response.message}"

  feed_xml = response.body
  ###
  # NB: Net::HTTP will NOT set encoding UTF-8 etc.
  # will mostly be ASCII
  # - try to change encoding to UTF-8 ourselves
  logger.debug "feed_xml.encoding.name (before): #{feed_xml.encoding.name}"

  #####
  # NB: ASCII-8BIT == BINARY == Encoding Unknown; Raw Bytes Here

  ## NB:
  # for now "hardcoded" to utf8 - what else can we do?
  # - note: force_encoding will NOT change the chars only change the assumed encoding w/o translation
  feed_xml = feed_xml.force_encoding( Encoding::UTF_8 )
  logger.debug "feed_xml.encoding.name (after): #{feed_xml.encoding.name}"

  ## check for md5 hash for response.body

  last_feed_md5 = feed_rec.md5
  feed_md5 = Digest::MD5.hexdigest( feed_xml )
  
  if last_feed_md5 && last_feed_md5 == feed_md5
    # not all servers handle conditional gets, so while not much can be
    # done about the bandwidth, but if the response body is identical
    # the downstream processing (parsing, caching, ...) can be avoided.
    #  - thanks to planet mars -fido.rb for the idea, cheers.
    
    puts "no change; md5 digests match; skipping parsing feed"
    return nil   # no updates available; nothing to do
  end

  feed_attribs = {
    http_code:          response.code.to_i,
    http_server:        response.header[ 'server' ],
    http_etag:          response.header[ 'etag' ],
    http_last_modified: response.header[ 'last-modified' ], ## note: last_modified header gets stored as plain text (not datetime)
    body:               feed_xml,
    md5:                feed_md5,
    fetched:            feed_fetched
  }

  ## if debug?
    puts "http header - server: #{response.header['server']} - #{response.header['server'].class.name}"
    puts "http header - etag: #{response.header['etag']} - #{response.header['etag'].class.name}"
    puts "http header - last-modified: #{response.header['last-modified']} - #{response.header['last-modified'].class.name}"
  ## end

  feed_rec.update_attributes!( feed_attribs )

  logger.debug "feed_xml:"
  logger.debug feed_xml[ 0..300 ] # get first 300 chars
    
  puts "Before parsing feed >#{feed_key}<..."

  ### move to feedutils
  ### logger.debug "using stdlib RSS::VERSION #{RSS::VERSION}"

  ## fix/todo: check for feed.nil?   -> error parsing!!!
  #    or throw exception
  feed = FeedUtils::Parser.parse( feed_xml )
end

#fetch_feed(url) ⇒ Object 



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# File 'lib/pluto/fetcher.rb', line 16

def fetch_feed( url )
  response = @worker.get( url )

  ## if debug?
    puts "http status #{response.code} #{response.message}"

    puts "http header - server: #{response.header['server']} - #{response.header['server'].class.name}"
    puts "http header - etag: #{response.header['etag']} - #{response.header['etag'].class.name}"
    puts "http header - last-modified: #{response.header['last-modified']} - #{response.header['last-modified'].class.name}"
  ## end

  xml = response.body

  ###
  # NB: Net::HTTP will NOT set encoding UTF-8 etc.
  # will mostly be ASCII
  # - try to change encoding to UTF-8 ourselves
  logger.debug "xml.encoding.name (before): #{xml.encoding.name}"

  #####
  # NB: ASCII-8BIT == BINARY == Encoding Unknown; Raw Bytes Here

  ## NB:
  # for now "hardcoded" to utf8 - what else can we do?
  # - note: force_encoding will NOT change the chars only change the assumed encoding w/o translation
  xml = xml.force_encoding( Encoding::UTF_8 )
  logger.debug "xml.encoding.name (after): #{xml.encoding.name}"      

  xml
end