Class: Dnsruby::ResolverRuby

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

Overview

This class implements the I/O using pure Ruby, with no dependencies.

Instance Method Summary collapse

Constructor Details

#initialize(parent) ⇒ ResolverRuby

:nodoc: all



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# File 'lib/Dnsruby/Resolver.rb', line 722

def initialize(parent)
  reset_attributes
  @parent=parent
end

Instance Method Details

#close ⇒ Object

Close the Resolver. Unfinished queries are terminated with OtherResolvError.



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# File 'lib/Dnsruby/Resolver.rb', line 807

def close
  @mutex.synchronize {
    @query_list.each do |client_query_id, values|
      msg, client_queue, q, outstanding = values
      send_result_and_close(client_queue, client_query_id, q, nil, OtherResolvError.new("Resolver closing!"))
    end
  }
end

#generate_timeouts ⇒ Object

:nodoc: all



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# File 'lib/Dnsruby/Resolver.rb', line 795

def generate_timeouts() #:nodoc: all
  # Create the timeouts for the query from the retry_times and retry_delay attributes. 
  # These are created at the same time in case the parameters change during the life of the query.
  # 
  # These should be absolute, rather than relative
  # The first value should be Time.now[      
  time_now = Time.now
  timeouts=@parent.generate_timeouts(time_now)
  return timeouts
end

#handle_error_response(select_queue, query_id, error, response) ⇒ Object

:nodoc: all



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# File 'lib/Dnsruby/Resolver.rb', line 921

def handle_error_response(select_queue, query_id, error, response) #:nodoc: all
  #Handle an error
  @mutex.synchronize{
    TheLog.debug("handling error #{error.class}, #{error}")
    # Check what sort of error it was :
    resolver, msg, client_query_id, retry_count = query_id
    msg, client_queue, select_queue, outstanding = @query_list[client_query_id]
    if (error.kind_of?(ResolvTimeout))
      #   - if it was a timeout, then check which number it was, and how many retries are expected on that server
      #       - if it was the last retry, on the last server, then return a timeout to the client (and clean up)
      #       - otherwise, continue
      # Do we have any more packets to send to this resolver?
      timeouts = @timeouts[client_query_id]
      if (outstanding.empty? && timeouts[1].values.empty?)
        TheLog.debug("Sending timeout to client")
        send_result_and_close(client_queue, client_query_id, select_queue, response, error)
      end
    elsif (error.kind_of?NXDomain)
      #   - if it was an NXDomain, then return that to the client, and stop all new queries (and clean up)
      send_result_and_close(client_queue, client_query_id, select_queue, response, error)
    else
      #   - if it was any other error, then remove that server from the list for that query
      #   If a Too Many Open Files error, then don't remove, but let retry work.
      timeouts = @timeouts[client_query_id]
      if (!(error.to_s=~/Errno::EMFILE/))
        TheLog.debug("Removing #{resolver.server} from resolver list for this query")
        timeouts[1].each do |key, value|
          res = value[0]
          if (res == resolver)
            timeouts[1].delete(key)
          end
        end
      else
        TheLog.debug("NOT Removing #{resolver.server} due to Errno::EMFILE")          
      end
      #        - if it was the last server, then return an error to the client (and clean up)
      if (outstanding.empty? && timeouts[1].values.empty?)
        #          if (outstanding.empty?)
        TheLog.debug("Sending error to client")
        send_result_and_close(client_queue, client_query_id, select_queue, response, error)
      end
    end
    #@TODO@ If we're still sending packets for this query, but none are outstanding, then 
    #jumpstart the next query?
  }
end

#handle_queue_event(queue, id) ⇒ Object

This method is called by the SelectThread (in the select thread) when the queue has a new item on it. The queue interface is used to separate producer/consumer threads, but we’re using it here in one thread. It’s probably a good idea to create a new “worker thread” to take items from the select thread queue and call this method in the worker thread.

Time to process a new queue event.



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# File 'lib/Dnsruby/Resolver.rb', line 879

def handle_queue_event(queue, id) #:nodoc: all
  # If we get a callback for an ID we don't know about, don't worry -
  # just ignore it. It may be for a query we've already completed.
  # 
  # So, get the next response from the queue (presuming there is one!)
  #
  # @TODO@ Tick could poll the queue and then call this method if needed - no need for observer interface.
  # @TODO@ Currently, tick and handle_queue_event called from select_thread - could have thread chuck events in to tick_queue. But then, clients would have to call in on other thread!
  #
  if (queue.empty?)
    TheLog.fatal("Queue empty in handle_queue_event!")
    raise RuntimeError.new("Severe internal error - Queue empty in handle_queue_event")
  end
  event_id, response, error = queue.pop
  # We should remove this packet from the list of outstanding packets for this query
  resolver, msg, client_query_id, retry_count = id
  if (id != event_id)
    TheLog.error("Serious internal error!! #{id} expected, #{event_id} received")
    raise RuntimeError.new("Serious internal error!! #{id} expected, #{event_id} received")
  end
  @mutex.synchronize{
    if (@query_list[client_query_id]==nil)
      TheLog.debug("Ignoring response for dead query")
      return
    end
    msg, client_queue, select_queue, outstanding = @query_list[client_query_id]
    if (!outstanding.include?id)
      TheLog.error("Query id not on outstanding list! #{outstanding.length} items. #{id} not on #{outstanding}")
      raise RuntimeError.new("Query id not on outstanding!")
    end
    outstanding.delete(id)
  }
  #      if (event.kind_of?(Exception))
  if (error != nil)
    handle_error_response(queue, event_id, error, response)
  else # if (event.kind_of?(Message))
    handle_response(queue, event_id, response)
    #      else
    #        TheLog.error("Random object #{event.class} returned through queue to Resolver")
  end
end

#handle_response(select_queue, query_id, response) ⇒ Object

:nodoc: all



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# File 'lib/Dnsruby/Resolver.rb', line 968

def handle_response(select_queue, query_id, response) #:nodoc: all
  # Handle a good response
  TheLog.debug("Handling good response")
  resolver, msg, client_query_id, retry_count = query_id
  @mutex.synchronize{
    query, client_queue, s_queue, outstanding = @query_list[client_query_id]
    if (s_queue != select_queue)
      TheLog.error("Serious internal error : expected select queue #{s_queue}, got #{select_queue}")
      raise RuntimeError.new("Serious internal error : expected select queue #{s_queue}, got #{select_queue}")
    end
    send_result_and_close(client_queue, client_query_id, select_queue, response, nil)
  }
end

#reset_attributes ⇒ Object

:nodoc: all



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# File 'lib/Dnsruby/Resolver.rb', line 726

def reset_attributes #:nodoc: all
  # data structures
  @mutex=Mutex.new
  @query_list = {}
  @timeouts = {}
end

#send_async(*args) ⇒ Object

msg, client_queue, client_query_id=nil)



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# File 'lib/Dnsruby/Resolver.rb', line 732

def send_async(*args) # msg, client_queue, client_query_id=nil)
  msg=args[0]
  client_queue=nil
  client_query_id=nil
  client_queue=args[1]
  if (args.length > 2)
    client_query_id = args[2]
  end

  
  # This is the whole point of the Resolver class.
  # We want to use multiple SingleResolvers to run a query.
  # So we kick off a system with select_thread where we send
  # a query with a queue, but log ourselves as observers for that
  # queue. When a new response is pushed on to the queue, then the
  # select thread will call this class' handler method IN THAT THREAD.
  # When the final response is known, this class then sticks it in
  # to the client queue.
  
  q = Queue.new
  if (client_query_id==nil)
    client_query_id = Time.now + rand(10000)
  end
  
  if (!client_queue.kind_of?Queue)
    TheLog.error("Wrong type for client_queue in Resolver#send_async")
    client_queue.push([client_query_id, ArgumentError.new("Wrong type of client_queue passed to Dnsruby::Resolver#send_async - should have been Queue, was #{client_queue.class}")])
    return
  end
  
  if (!msg.kind_of?Message)
    TheLog.error("Wrong type for msg in Resolver#send_async")
    client_queue.push([client_query_id, ArgumentError.new("Wrong type of msg passed to Dnsruby::Resolver#send_async - should have been Message, was #{msg.class}")])
    return
  end
  
  tick_needed=false
  # add to our data structures
  @mutex.synchronize{
    tick_needed = true if @query_list.empty?
    if (@query_list.has_key?client_query_id)
      TheLog.error("Duplicate query id requested (#{client_query_id}")
      client_queue.push([client_query_id, ArgumentError.new("Client query ID already in use")])
      return
    end
    outstanding = []
    @query_list[client_query_id]=[msg, client_queue, q, outstanding]
    
    query_timeout = Time.now+@parent.query_timeout
    if (@parent.query_timeout == 0)
      query_timeout = Time.now+31536000 # a year from now
    end
    @timeouts[client_query_id]=[query_timeout, generate_timeouts()]
  }
  
  # Now do querying stuff using SingleResolver
  # All this will be handled by the tick method (if we have 0 as the first timeout)
  st = SelectThread.instance
  st.add_observer(q, self)
  tick if tick_needed
  return client_query_id
end

#send_result_and_close(client_queue, client_query_id, select_queue, msg, error) ⇒ Object

MUST BE CALLED IN A SYNCHRONIZED BLOCK!

Send the result back to the client, and close the socket for that query by removing the query from the select thread.



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# File 'lib/Dnsruby/Resolver.rb', line 820

def send_result_and_close(client_queue, client_query_id, select_queue, msg, error) #:nodoc: all
  # We might still get some callbacks, which we should ignore
  st = SelectThread.instance
  st.remove_observer(select_queue, self)
  #      @mutex.synchronize{
  # Remove the query from all of the data structures
  @timeouts.delete(client_query_id)
  @query_list.delete(client_query_id)
  #      }
  # Return the response to the client
  client_queue.push([client_query_id, msg, error])
end

#tick ⇒ Object

This method is called ten times a second from the select loop, in the select thread. It should arguably be called from another worker thread… Each tick, we check if any timeouts have occurred. If so, we take the appropriate action : Return a timeout to the client, or send a new query



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# File 'lib/Dnsruby/Resolver.rb', line 837

def tick #:nodoc: all
  # Handle the tick
  # Do we have any retries due to be sent yet?
  @mutex.synchronize{
    time_now = Time.now
    @timeouts.keys.each do |client_query_id|
      msg, client_queue, select_queue, outstanding = @query_list[client_query_id]
      query_timeout, timeouts = @timeouts[client_query_id]
      if (query_timeout < Time.now)
        #Time the query out
        send_result_and_close(client_queue, client_query_id, select_queue, nil, ResolvTimeout.new("Query timed out"))
        next
      end
      timeouts_done = []
      timeouts.keys.sort.each do |timeout|
        if (timeout < time_now)
          # Send the next query
          res, retry_count = timeouts[timeout]
          id = [res, msg, client_query_id, retry_count]
          TheLog.debug("Sending msg to #{res.server}")
          # We should keep a list of the queries which are outstanding
          outstanding.push(id)
          timeouts_done.push(timeout)
          timeouts.delete(timeout)
          res.send_async(msg, select_queue, id)
        else
          break
        end
      end
      timeouts_done.each do |t|
        timeouts.delete(t)
      end
    end
  }
end