Class: Zillabyte::Runner::MultilangOperation

Inherits:
Object
  • Object
show all
Defined in:
lib/zillabyte/runner/multilang_operation.rb

Overview

Emulate a multilang operation

Constant Summary collapse

HANDSHAKE_MESSAGE = 
"{\"pidDir\": \"/tmp\"}\n"
DONE_MESSAGE = 
"{\"command\": \"done\"}\n"
NEXT_MESSAGE = 
"{\"command\": \"next\"}\n"
BEGIN_CYCLE_MESSAGE = 
"{\"command\": \"begin_cycle\"}\n"
END_CYCLE_MESSAGE = 
"{\"command\": \"end_cycle\"}\n"
PONG_PREFIX = 
"{\"pong\": \""
PONG_SUFFIX = 
"\"}\n"
ENDMARKER = 
"\nend\n"

Class Method Summary collapse

Class Method Details

.begin_cycle(write_stream, read_stream) ⇒ Object

Instruct multilang to begin cycle



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# File 'lib/zillabyte/runner/multilang_operation.rb', line 1038

def self.begin_cycle(write_stream, read_stream)
  begin
    write_message(write_stream, BEGIN_CYCLE_MESSAGE)
    msg = read_message(read_stream)
    obj = Hash[msg]
    if obj["command"] != "done"
      raise "Invalid response from multilang #{msg}"
    end
  rescue Exception => e
    cdisplay(e)
  end
end

.build_tuple_json(tuple, meta = nil, column_aliases = nil) ⇒ Object

Build a tuple and format into JSON



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# File 'lib/zillabyte/runner/multilang_operation.rb', line 1090

def self.build_tuple_json(tuple, meta = nil, column_aliases = nil)
  meta ||= {}
  column_aliases ||= {}
  values = {}
  tuple.each do |k, v|
   if(k == "id")
     next
   elsif(k == "confidence" or k == "since" or k == "source")
     meta[k] = v
   else  
    values[k] = v
   end
  end
  tuple_json = {"tuple" => values, "meta" => meta, "column_aliases" => column_aliases}.to_json
  return tuple_json
end

.cdisplay(msg) ⇒ Object

Display a colored, formatted message



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# File 'lib/zillabyte/runner/multilang_operation.rb', line 1135

def self.cdisplay(msg)
  @__tester.cdisplay(@__name, msg)
end

.command(arg, ignore_stderr = false) ⇒ Object

Construct a multilang command



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# File 'lib/zillabyte/runner/multilang_operation.rb', line 1109

def self.command(arg, ignore_stderr=false)
  cdisplay("could not extract meta information. missing zillabyte.conf.yml?") if @__meta.nil?

  full_script = File.join(@__dir, @__meta["script"])
  stderr_opt = "2> /dev/null" if ignore_stderr

  case @__meta["language"]
  when "ruby"
    # Execute in the bundler context
    cmd = "cd \"#{@__dir}\"; unset BUNDLE_GEMFILE; ZILLABYTE_HARNESS=1 bundle exec ruby \"#{full_script}\" #{arg}  #{stderr_opt}"
  when "python"#{
    if(File.directory?("#{@__dir}/vEnv"))
      cmd = "cd \"#{@__dir}\"; PYTHONPATH=~/zb1/multilang/python/Zillabyte #{@__dir}/vEnv/bin/python \"#{full_script}\" #{arg}  #{stderr_opt}"
    else
      cmd = "cd \"#{@__dir}\"; PYTHONPATH=~/zb1/multilang/python/Zillabyte python \"#{full_script}\" #{arg}  #{stderr_opt}"
    end
  when "js"
    cmd = "cd \"#{@__dir}\"; NODE_PATH=~/zb1/multilang/js/src/lib #{Zillabyte::API::NODEJS_BIN}  \"#{full_script}\" #{arg} #{stderr_opt}"
  else
    cdisplay("no language specified")
  end
  return cmd
end

.emit_consumer_tuple(stream, consumer, tuple_json) ⇒ Object

Emit tuple_json to the consumer of a stream



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# File 'lib/zillabyte/runner/multilang_operation.rb', line 1076

def self.emit_consumer_tuple(stream, consumer, tuple_json)
  begin
    display_json = Hash[JSON.parse(tuple_json)["tuple"].map {|k,v| [truncate_message(k), truncate_message(v)]}].to_json
  rescue JSON::ParserError
    cdisplay "Error: invalid JSON"
  end
  write_stream = get_write_stream(stream, consumer)
  write_message(write_stream, tuple_json)
  @__emit_queues[stream][consumer][:ready] = false
  cdisplay "emitted tuple #{display_json} to #{consumer} "
end

.get_consumer_tuple(stream, consumer) ⇒ Object

Get tuple for sending to consumer of stream



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# File 'lib/zillabyte/runner/multilang_operation.rb', line 1070

def self.get_consumer_tuple(stream, consumer)
  @__emit_queues[stream][consumer][:write_queue].shift
end

.get_write_stream(stream, consumer) ⇒ Object

Get the write pipe of the stream consumer



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# File 'lib/zillabyte/runner/multilang_operation.rb', line 1064

def self.get_write_stream(stream, consumer)
   @__consumer_pipes[stream][consumer][:wr_parent]
end

.handshake(write_stream, read_stream) ⇒ Object

Handshake connection to multilang



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# File 'lib/zillabyte/runner/multilang_operation.rb', line 1025

def self.handshake(write_stream, read_stream)
  begin
    write_message write_stream, HANDSHAKE_MESSAGE
    msg = read_message(read_stream)
  rescue Exception => e
    cdisplay(e)
    cdisplay("Error handshaking node")
    raise e
  end
end

.read_message(read_stream) ⇒ Object

Read a JSON message



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# File 'lib/zillabyte/runner/multilang_operation.rb', line 952

def self.read_message(read_stream)

  @__read_buffers[read_stream] ||= ""
  @__read_buffered_messages[read_stream] ||= []
  if !@__read_buffered_messages[read_stream].empty?
      obj = @__read_buffered_messages[read_stream].shift
    return obj
  end

  # read message from stream
  loop do

    while !@__read_buffers[read_stream].include? ENDMARKER

      segment = read_stream.sysread(BUFSIZE)
      @__read_buffers[read_stream] << segment
    end

    # cdisplay "READMESSAGE: read #{segment.length} bytes, read buffer length : #{@__read_buffer.length}"
    # TODO this include is redundant
    read_buffer = @__read_buffers[read_stream]
    if read_buffer.include? ENDMARKER
      objs = read_buffer.split(ENDMARKER)
      ends = read_buffer.scan(ENDMARKER)
      if objs.count == ends.count # We have a full number of messages
        objs.each do |obj|
          begin
            @__read_buffered_messages[read_stream] << JSON.parse(obj)
            # cdisplay "READMESSAGE: got hash #{hash}"
          rescue JSON::ParserError 
            cdisplay "READMESSAGE: invalid JSON #{obj}"
          end
        end
        @__read_buffers[read_stream] = ""
        return @__read_buffered_messages[read_stream].shift
      else

        (0..ends.count-1).each do |i|
          obj = objs[i] 
          begin
            @__read_buffered_messages[read_stream] << JSON.parse(obj)
          rescue JSON::ParserError 
            cdisplay "READMESSAGE: invalid JSON #{obj}" 
          end
        end

       # cdisplay "adding leftovers : \n  #{objs[ends.count..-1]}"
        @__read_buffers[read_stream] = objs[ends.count..-1].join(ENDMARKER)
        return @__read_buffered_messages[read_stream].shift
      end
    end
  end
end

.run(node, dir, consumee, consumer_pipes, tester, meta, options = {}) ⇒ Object 



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# File 'lib/zillabyte/runner/multilang_operation.rb', line 18

def self.run(node, dir, consumee, consumer_pipes, tester, meta, options = {})

  @__node = node
  @__name = node["name"]
  @__type = node["type"]
  @__dir = dir
  @__consumee = consumee
  @__consumer_pipes = consumer_pipes
  @__tester = tester

  @__meta = meta
  @__options = options
  @__output_type = options[:output_type]

  # Each consumer of a stream gets its own queue and message passing
  @__emit_queues = {}
  @__consumer_pipes.each_pair do |stream, consumers|
    consumers.each_key do |consumer|
      @__emit_queues[stream] ||= {}
      @__emit_queues[stream][consumer] = {:write_queue => [], :ready => true}
    end
  end

  begin
    case @__type
    when "source"
      self.run_source()
    when "group_by"
      self.run_group_by()
    when "each"
      self.run_each()
    when "filter"
      self.run_filter()
    when "component"
      Zillabyte::Runner::ComponentOperation.run(node, dir, consumee, consumer_pipes, tester, meta, options = {})
    when "sink"
      self.run_sink()
    else
      cdisplay("invalid operation type #{@__type}")
    end
  rescue => e
    cdisplay e.message
    cdisplay e.backtrace
  end
end

.run_each ⇒ Object 



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# File 'lib/zillabyte/runner/multilang_operation.rb', line 394

def self.run_each()

  # Index streams and consumers by their pipes for lookup
  consumer_hash = {}
  @__emit_queues.each_pair do |stream, consumers|
    consumers.each_key do |consumer|
      read_stream = @__consumer_pipes[stream][consumer][:rd_parent]
      consumer_hash[read_stream] = {:stream => stream, :consumer => consumer}
    end
  end


  # Keep track of how many consumers to handle before exiting
  consumers_running = consumer_hash.keys.length

  # Setup multilang pipe
  ml_pipe = "#{@__name}_pipe"
  if File.exists?("#{ml_pipe}.in")
    File.delete("#{ml_pipe}.in")
  end
  File.mkfifo("#{ml_pipe}.in")

  cmd = command("--execute_live --name #{@__name} --pipe #{ml_pipe}")
  begin
    # Start the operation... 
    Open3.popen3(cmd) do |ml_input, stdout, stderr, wait_thread|
      begin

        # Multilang output tuples
        ml_output = File.open("#{ml_pipe}.in", "r+")

        # Setup streams from consumers, multilang, and the consumee
        read_streams = consumer_hash.keys.concat [@__consumee[:rd_child], ml_output, stdout]

        # Handshake
        handshake(ml_input, ml_output)

        # Begin cycle
        multilang_queue = []
        mutlilang_count = 0
        end_cycle_received = false


        # Receive and handle messages
        loop do

          # Read from a stream
          rs = select_read_streams(read_streams)
          rs.each do |r|

            # Read STDOUT from program straight to user
            if r == stdout
              msg = r.gets
              msg = msg.sub(/\n/, "")
              cdisplay("LOG: #{msg}")
              next
            end

            # Receive an object
            obj = read_message(r)

            if obj["command"] 
              case obj["command"]

              # Multilang emitted a tuple
              when "emit"

                stream = obj["stream"]
               
                # Send or enqueue tuple for each consumer
                tuple_json = build_tuple_json(obj['tuple'], obj['meta'], obj['column_aliases'])

                @__emit_queues[stream].each_pair do |consumer, emitter|
                  if emitter[:ready]
                    emit_consumer_tuple(stream, consumer, tuple_json)
                  else
                    @__emit_queues[stream][consumer][:write_queue] << tuple_json
                  end
                end

              # Consumer is ready for a message
              when "next"

                stream = consumer_hash[r][:stream]
                consumer = consumer_hash[r][:consumer]

                @__emit_queues[stream][consumer][:ready] = true
                tuple_json = get_consumer_tuple(stream, consumer)

                # End cycle for consumer if it has processed all tuples
                if tuple_json.nil? && end_cycle_received
                  write_stream = get_write_stream(stream, consumer)
                  write_message(write_stream, END_CYCLE_MESSAGE)
                  consumers_running -= 1
                  if consumers_running == 0
                    break
                  end


                  # TODO break if last consumer
                elsif !tuple_json.nil?
                  # Emit tuple to consumer
                  emit_consumer_tuple(stream, consumer, tuple_json)
                  emitted = true
                end

              # Multilang is done emitting a group of tuples
              when "done" 
                mutlilang_count -= 1                  

                # Send the next tuple to multilang
                if !multilang_queue.empty?
                  write_message(ml_input, multilang_queue.shift)

                # Request next tuple from consumee
                elsif !end_cycle_received
                  write_message(@__consumee[:wr_child], NEXT_MESSAGE)
                  

                # If there are no more messages to send, we are done
                elsif end_cycle_received && mutlilang_count == 0
                  finished = true

                 # End cycle for ready consumers
                  @__emit_queues.each_pair do |stream, consumers|
                    consumers.each_pair do |consumer, emitter|
                      if emitter[:ready]
                        write_stream = get_write_stream(stream, consumer)
                        write_message(write_stream, END_CYCLE_MESSAGE)
                        consumers_running -= 1
                        if consumers_running == 0
                          break
                        end
                      end
                    end
                  end
                end

              # Multilang sent an error message
              when "fail"
                cdisplay("ERROR : #{obj['msg']}")
              
              # Multilang sent a log message
              when "log"
                cdisplay "LOG: #{obj['msg']}"

              # Consumee operation sent signal to end_cycle
              when "end_cycle"
                end_cycle_received = true

                if mutlilang_count == 0
                  @__emit_queues.each_pair do |stream, consumers|
                    consumers.each_pair do |consumer, emitter|                      
                      if emitter[:ready]
                        write_stream = get_write_stream(stream, consumer)
                        write_message(write_stream, END_CYCLE_MESSAGE)
                        consumers_running -= 1
                        if consumers_running == 0
                          break
                        end
                      end
                    end
                  end

                end

              end

            # Received a tuple from consumee
            elsif obj['tuple']
            
              # Send or enqueue to multilang
              mutlilang_count += 1
              if multilang_queue.empty?
                write_message(ml_input, obj.to_json)
              else
                multilang_queue << obj.to_json
              end
            
            # Multilang sent a ping
            elsif obj['ping']
              write_message(ml_input, PONG_PREFIX + "#{Time.now.utc.to_f}" + PONG_SUFFIX)
            end
          end

          # Exit after ending consumer cycles
          if consumers_running == 0
            break
          end

        end
      rescue Errno::EIO
         cdisplay("Errno:EIO error")
      ensure
        # cleanup
        pid = wait_thread[:pid] 
        ml_input.close  
        ml_output.close
        File.delete("#{ml_pipe}.in")
        stdout.close
        stderr.close
        Process.kill('INT', pid)
      end
    end
  rescue PTY::ChildExited
    cdisplay("The child process exited!")
  end
end

.run_filter ⇒ Object 



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# File 'lib/zillabyte/runner/multilang_operation.rb', line 842

def self.run_filter()
  self.run_each()
end

.run_group_by ⇒ Object 



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# File 'lib/zillabyte/runner/multilang_operation.rb', line 604

def self.run_group_by()

  # Index streams and consumers by their pipes for lookup
  consumer_hash = {}
  @__emit_queues.each_pair do |stream, consumers|
    consumers.each_key do |consumer|
      read_stream = @__consumer_pipes[stream][consumer][:rd_parent]
      consumer_hash[read_stream] = {:stream => stream, :consumer => consumer}
    end
  end

  # Keep track of how many consumers to handle before exiting
  consumers_running = consumer_hash.keys.length

  # Setup groups
  group_by = @__node['group_by']
  group_tuples = {}
  emit_count = 0    # used to track how many emits are expected once groups are sent to multilang
  emitted_tuples = [] # used to send to consumers after once groupings are emitted
  tuple_queue = []

  # Setup multilang pipe
  ml_pipe = "#{@__name}_pipe"
  if File.exists?("#{ml_pipe}.in")
    File.delete("#{ml_pipe}.in")
  end
  File.mkfifo("#{ml_pipe}.in")
  
  cmd = command("--execute_live --name #{@__name} --pipe #{ml_pipe}")
  begin
    # Start the operation... 
    Open3.popen3(cmd) do |ml_input, stdout, stderr, wait_thread|
      begin

        # Multilang output tuples
        ml_output = File.open("#{ml_pipe}.in", "r+")
        # Setup streams from consumers, multilang, and the consumee
        read_streams = consumer_hash.keys.concat [stdout, ml_output, @__consumee[:rd_child]]

        # Handshake
        handshake(ml_input, ml_output)

        # Begin cycle
        end_cycle_received = false
        finished_emitting = false

        # select a stream
        loop do

          # Read from a stream
          rs = select_read_streams(read_streams)
          rs.each do |r|

            # Read STDOUT from program straight to user
            if r == stdout
              msg = r.gets
              msg = msg.sub(/\n/, "")
              cdisplay("log: #{msg}")
              next
            end


            # Receive an object
            obj = read_message(r)
          
            if obj["command"] 
              case obj["command"]

              when "done"

                if end_cycle_received
                  tuple_json = tuple_queue.shift
                  if !tuple_json.nil?
                    write_message(ml_input, tuple_json)
                  end
                end

                next

              # Begin aggregation
              when "end_cycle"
                end_cycle_received = true
                read_streams = [ml_output]

                group_tuples.each do |group_tuple, tuples|
                  tuple_queue << "{\"command\": \"begin_group\", \"tuple\": #{group_tuple.to_json}, \"meta\":{}}\n"
                  tuples.each do |t|
                    tuple_queue << "{\"command\": \"aggregate\", #{t}}\n"
                  end
                 tuple_queue << "{\"command\": \"end_group\"}\n"

                  # keep track of how many emits are expected
                  emit_count += 1
                end

                tuple_json = tuple_queue.shift
                if !tuple_json.nil?
                  write_message(ml_input, tuple_json)
                end

              # Multilang has emitted a grouped tuple
              when "emit"
                stream = obj['stream']
                emit_count -= 1
                # Enqueue for consumers
                tuple_json = build_tuple_json(obj['tuple'], obj['meta'], obj['column_aliases'])
                @__emit_queues.each_pair do |stream, consumers|
                  consumers.each_key do |consumer|
                    @__emit_queues[stream][consumer][:write_queue] << tuple_json  
                  end
                end

                # End cycle when done emitting
                if end_cycle_received && emit_count == 0
                  finished_emitting = true
                  break      
                elsif end_cycle_received
                  tuple_json = tuple_queue.shift
                  if !tuple_json.nil?
                    write_message(ml_input, tuple_json)
                  end
                end

              end

            # Received a tuple from operation
            elsif obj["tuple"]
              tuple = obj["tuple"].to_json
              meta = obj["meta"].to_json
              column_aliases = obj["column_aliases"] || {}
              aliases = Hash[column_aliases.map{|h| [h["alias"],h["concrete_name"]]}]
              gt = {}

              # Get the column names to group on
              group_by.each do |field|
                field_name = aliases[field] || field
                gt[field] = obj["tuple"][field_name]
              end

              msg_no_brackets = "\"tuple\": #{tuple}, \"meta\": #{meta}, \"column_aliases\": #{column_aliases.to_json}"

              # Group tuple into existing group or create new group
              if group_tuples[gt]
                group_tuples[gt] << msg_no_brackets
              else
                group_tuples[gt] = [msg_no_brackets]
              end

              # Ask operation for next tuple
              write_message(@__consumee[:wr_child], NEXT_MESSAGE)

            # Multilang sent a ping
            elsif obj['ping']
              write_message(ml_input, PONG_PREFIX + "#{Time.now.utc.to_f}" + PONG_SUFFIX)
            end
          end

          # Send tuples to consumers
          if finished_emitting && consumers_running > 0

            # Send first tuple
            @__emit_queues.each_pair do |stream, consumers|
              consumers.each_key do |consumer|
                tuple_json = get_consumer_tuple(stream, consumer)
                emit_consumer_tuple(stream, consumer, tuple_json)
              end
            end

            # Sent tuples to consumers as appropriate
            loop do 

              # Retrieve messages from consumers
              rs, ws, es = IO.select(consumer_hash.keys, [], [])

              # Emit tuples to consumers
              emitted = false
              rs.each do |r|

                # Read from consumer
                msg = read_message(r)
                consumer = consumer_hash[r][:consumer]
                stream = consumer_hash[r][:stream]

                # Consumer is ready for next message
                if msg["command"] && msg["command"] == "next"

                  @__emit_queues[stream][consumer][:ready] = true
                  tuple_json = get_consumer_tuple(stream, consumer)

                  # If all messages have been sent to a consumer, end its cycle
                  if tuple_json.nil?
                    write_stream = get_write_stream(stream, consumer)
                    write_message(write_stream, END_CYCLE_MESSAGE)
                    consumers_running -= 1
                    if consumers_running == 0
                      break
                    end
                  else
                    # Emit tuple to consumer
                    emit_consumer_tuple(stream, consumer, tuple_json)
                    emitted = true
                  end
                end

              end
               # Exit when done emitting
              if !emitted
                return
              end
            end
            break

          # Exit after ending all consumer cycles
          elsif consumers_running == 0
            break
          end

          
        end
      rescue Errno::EIO
         cdisplay("Errno:EIO error")
      ensure
        # cleanup
        pid = wait_thread[:pid]  
        ml_input.close 
        ml_output.close
        File.delete("#{ml_pipe}.in")
        stdout.close
        stderr.close
        Process.kill('INT', pid)
      end  
    end
  rescue PTY::ChildExited
    cdisplay("The child process exited!")
  end
end

.run_sink ⇒ Object

Send a message to all consumers of the operation



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# File 'lib/zillabyte/runner/multilang_operation.rb', line 848

def self.run_sink()
  output = @__options[:output]
  messages = []
  loop do
    # Read messages
    msg = read_message(@__consumee[:rd_child])
    obj = msg

    # Add row
    if obj['tuple']
      messages << msg
      display_json = Hash[obj['tuple'].map{|k, v| [truncate_message(k), truncate_message(v)]}].to_json
      if @__options[:interactive]
        cdisplay "received #{display_json}"
      end
      write_message(@__consumee[:wr_child], NEXT_MESSAGE)

    # End cycle
    elsif obj['command'] && obj['command'] == "end_cycle"
      break
    end
  end

  if messages.empty?
    cdisplay "empty relation"
    cdisplay "use Ctrl-C to exit"
    return
  end

  # Build table
  table = Terminal::Table.new :title => @__name
  csv_str = CSV.generate do |csv|
    header_written = false;
    messages.each do |obj|
      begin

        t = obj['tuple']
        m = obj['meta'] || {}

         if t
          if header_written == false
            keys = [t.keys, m.keys].flatten
            csv << keys
            table << keys
            table << :separator
            header_written = true
          end

          vals = [t.values, m.values].flatten
          csv << vals
          table << vals.flat_map{|v| "#{v}"[0..100]}
        end
      rescue JSON::ParserError
        cdisplay("invalid JSON")
        next
      rescue Exception => e
        cdisplay e
      end
    end
  end

  # Output table
  cdisplay("\n#{table.to_s}")
  cdisplay ""
    
  # Write file
  if output
    filename = "#{output}.csv"
    f = File.open(filename, "w")
    f.write(csv_str)
    f.close()
    cdisplay("output written to #{filename}")
  end
  cdisplay "\n \nPress Ctrl-C to exit"
end

.run_source ⇒ Object 



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# File 'lib/zillabyte/runner/multilang_operation.rb', line 65

def self.run_source()

  end_cycle_policy = @__node["end_cycle_policy"]

  # Interactive source
  if @__options[:interactive]
    loop do 

      msg = @__consumee[:rd_child].gets

        # Build tuple
        begin
          tuple = JSON.parse(msg)
        rescue JSON::ParserError 
          cdisplay "Error: invalid JSON"           
          next
        end

        tuple_json = build_tuple_json(tuple)
        display_json = Hash[JSON.parse(tuple_json)["tuple"].map {|k,v| [truncate_message(k), truncate_message(v)]}].to_json
        send_to_consumers(tuple_json)   
    end

  # Source from relation
  elsif @__node['matches'] or @__node["relation"]

    # Query API for rows  
    matches = @__node['matches'] || (@__node["relation"]["query"])
    cdisplay("Fetching remote data...")
    res = @__tester.query_agnostic(matches)
    rows = res["rows"]
    if(rows.nil? or rows.length == 0)
      cdisplay("Could not find data that matches your 'matches' clause")
      exit(-1)
    end
    cdisplay("Received #{rows.length} rows!")

    # Enqueue rows for sending to consumers
    column_aliases = res["column_aliases"]
    rows.each do |tuple|
      tuple_json = build_tuple_json(tuple, nil, column_aliases)

      @__emit_queues.each_pair do |stream, consumers|
        consumers.each_pair do |consumer, emitter|
          emitter[:write_queue] << tuple_json
        end
      end
    end

    # Index streams and consumers by their pipes for lookup
    consumer_hash = {}
    @__emit_queues.each_pair do |stream, consumers|
      consumers.each_key do |consumer|
        read_stream = @__consumer_pipes[stream][consumer][:rd_parent]
        consumer_hash[read_stream] = {:stream => stream, :consumer => consumer}
      end
    end


    # Send first tuple
    @__emit_queues.each_pair do |stream, consumers|
      consumers.each_key do |consumer|
        tuple_json = get_consumer_tuple(stream, consumer)
        emit_consumer_tuple(stream, consumer, tuple_json)
      end
    end

    # Sent tuples to consumers as appropriate
    loop do 

      # Retrieve messages from consumers
      rs, ws, es = IO.select(consumer_hash.keys, [], [])

      # Emit tuples to consumers
      emitted = false
      rs.each do |r|

        # Read from consumer
        msg = read_message(r)

        stream = consumer_hash[r][:stream]
        consumer = consumer_hash[r][:consumer]

        # Consumer is ready for next message
        if msg["command"] && msg["command"] == "next"

          @__emit_queues[stream][consumer][:ready] = true
          tuple_json = get_consumer_tuple(stream, consumer)

          # If all messages have been sent to consumer, end their cycle
          if tuple_json.nil?
            write_stream = get_write_stream(stream, consumer)
            cdisplay "ending cycle for #{consumer}"
            write_message(write_stream, END_CYCLE_MESSAGE)
            write_message(write_stream, DONE_MESSAGE)

          else
            # Emit tuple to consumer
            emit_consumer_tuple(stream, consumer, tuple_json)
            emitted = true
          end
        end
      end

      # Exit when done emitting
      if !emitted
        return
      end
    end
    
  # Custom source
  else

    # Index streams and consumers by their pipes for lookup

    consumer_hash ={}
    @__emit_queues.each_pair do |stream, consumers|
      consumers.each_key do |consumer|
        read_stream = @__consumer_pipes[stream][consumer][:rd_parent]
        consumer_hash[read_stream] = {:stream => stream, :consumer => consumer}
      end
    end

    # Keep track of how many consumers to handle before exiting
    consumers_running = consumer_hash.keys.length

    # Setup multilang pipe
    ml_pipe = "#{@__name}_pipe"
    if File.exists?("#{ml_pipe}.in")
      File.delete("#{ml_pipe}.in")
    end
    File.mkfifo("#{ml_pipe}.in")


    # Spawn multilang process
    cmd = command("--execute_live --name #{@__name} --pipe #{ml_pipe}")
    begin

      Open3.popen3(cmd) do |ml_input, stdout, stderr, wait_thread|
        begin

          # Multilang output tuples
          ml_output = File.open("#{ml_pipe}.in", "r")

          # Setup streams from consumers and multilang
          read_streams = consumer_hash.keys.concat [stdout, ml_output]

          # Handshake
          handshake(ml_input, ml_output)

          # Begin cycle
          begin_cycle(ml_input, ml_output)
          emitted = false
          write_message(ml_input, NEXT_MESSAGE)
          multilang_queue = []
          end_cycle_policy = @__options[:end_cycle_policy]
          end_cycle_received = false

          # Receive and handle messages
          loop do
           
            # Read from a stream
            rs = select_read_streams(read_streams)
            rs.each do |r|

              # Read stdout straight to user
              if r == stdout && consumers_running > 0
                msg = r.gets
                msg = msg.sub(/\n/, "")
                cdisplay("log: #{msg}")
                next
              end

              obj = read_message(r)

              if obj.nil?
                next
              end

              if obj["command"] 
                case obj["command"]

                # Multilang emitted a tuple
                when "emit"

                  stream = obj['stream']
                  # Check for null emit
                  if end_cycle_policy != "explicit"

                    if obj['tuple'].nil?
                      end_cycle_received = true
                    else
                      nil_values = false
                      obj['tuple'].each_value do |v|
                        if v.nil?
                          nil_values = true
                          break       
                        end                     
                      end
                      end_cycle_received = nil_values
                      next unless !end_cycle_received
                    end
                  end

                  # Valid emit
                  emitted = true

                  # Send or enqueue tuple for each consumer
                  tuple_json = build_tuple_json(obj['tuple'], obj['meta'], obj['column_aliases'])

 
                  @__emit_queues[stream].each_pair do |consumer, emitter|
                    if emitter[:ready]
                      emit_consumer_tuple(stream, consumer, tuple_json)
                    else
                      @__emit_queues[stream][consumer][:write_queue] << tuple_json
                    end
                  end

                # Consumer is ready for a message
                when "next"
                  stream = consumer_hash[r][:stream]
                  consumer = consumer_hash[r][:consumer]
                  @__emit_queues[stream][consumer][:ready] = true
                  tuple_json = get_consumer_tuple(stream, consumer)

                  # End cycle for consumer if it has processed all tuples
                  if tuple_json.nil? && end_cycle_received

                    write_stream = get_write_stream(stream, consumer)
                    write_message(write_stream, END_CYCLE_MESSAGE)
                    consumers_running -= 1
                    if consumers_running == 0
                      break
                    end

                    # TODO break if last consumer
                  elsif !tuple_json.nil?
                    # Emit tuple to consumer
                    emit_consumer_tuple(stream, consumer, tuple_json)
                    emitted = true
                  end

                # Multilang is done emitting a group of tuples
                when "done"
                  # End cycle if no tuples were emitted
                  if !emitted && end_cycle_policy == "null_emit"
                    end_cycle_received = true
                  else
                    emitted = false
                  end
                
                  # Send the next tuple to multilang
                  if !multilang_queue.empty?
                    write_message(ml_input, multilang_queue.shift)

                  # Request next tuple from mutilang
                  elsif !end_cycle_received
                    write_message(ml_input, NEXT_MESSAGE)

                  # If there are no more messages to send, we are done
                  else end_cycle_received
                    finished = true
                     # End cycle for ready consumers
                    @__emit_queues.each_pair do |stream, consumers|
                      consumers.each_pair do |consumer, emitter|
                        if emitter[:ready]
                          write_stream = get_write_stream(stream, consumer)
                          write_message(write_stream, END_CYCLE_MESSAGE)
                          consumers_running -= 1
                          if consumers_running == 0
                            break
                          end
                        end
                      end

                    end
                  end

                # Multilang sent an error message
                when "fail"
                  cdisplay("ERROR : #{obj['msg']}")
                
                # Multilang sent a log message
                when "log"
                  cdisplay "LOG: #{obj['msg']}"

                # Multilang sent signal to end the cycle
                when "end_cycle"
                  if end_cycle_policy != "explicit"
                    cdisplay "received end_cycle command for non explicit policy"
                    next
                  end
                  end_cycle_received = true

                end
              
              # Multilang sent a ping
              elsif obj['ping']
                write_message(ml_input, PONG_PREFIX + "#{Time.now.utc.to_f}" + PONG_SUFFIX)
              end
            end

            # Exit after ending consumer cycles
            if consumers_running == 0
              return
            end
            
          end
        rescue Errno::EIO
           cdisplay("Errno:EIO error")
        ensure
          # cleanup
          pid = wait_thread[:pid] 
          ml_input.close
          ml_output.close
          File.delete("#{ml_pipe}.in")
          stdout.close
          stderr.close
          Process.kill('INT', pid)
        end
      end
    rescue PTY::ChildExited
      cdisplay("The child process exited!")
    end
  end
end

.select_read_streams(read_streams) ⇒ Object

Return availible reading streams



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# File 'lib/zillabyte/runner/multilang_operation.rb', line 935

def self.select_read_streams(read_streams)

  rs = []
  read_streams.each do |read_stream|
    @__read_buffered_messages[read_stream] ||= []
    if !@__read_buffered_messages[read_stream].empty?
      rs << read_stream
    end
  end
  return rs unless rs.empty?

  rs, ws, es = IO.select(read_streams, [], [])
  return rs
end

.send_to_consumers(json_obj) ⇒ Object

Send object to every consumer of the operation, regardless of stream



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# File 'lib/zillabyte/runner/multilang_operation.rb', line 1053

def self.send_to_consumers(json_obj)
  @__consumer_pipes.each_pair do |stream, consumers|
    consumers.each_pair do |consumer, pipe| 
      write_message(pipe[:wr_parent], json_obj)
      cdisplay "emitted #{json_obj} to #{consumer}"
    end
  end
end

.truncate_message(msg) ⇒ Object

Format a message for display



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# File 'lib/zillabyte/runner/multilang_operation.rb', line 1015

def self.truncate_message(msg)
  return msg if(!msg.instance_of?(String))
  t_length = 50 # truncates entries to this length
  m_length = msg.length
  msg_out = m_length > t_length ? msg[0..t_length-3]+"..." : msg
  msg_out
end

.write_message(write_stream, msg) ⇒ Object

Write JSON message



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# File 'lib/zillabyte/runner/multilang_operation.rb', line 1008

def self.write_message(write_stream, msg)
  write_msg = msg.strip + ENDMARKER
  write_stream.write write_msg
  write_stream.flush
end