LOGSTASH-1003 LOGSTASH-1038 fixing both issues in one commit because the rabbitmq input is functionally broken until both are fixed

lib/logstash/inputs/rabbitmq.rb

@@ -64,10 +64,20 @@ class LogStash::Inputs::RabbitMQ < LogStash::Inputs::Threadable
   # Is the queue exclusive? (aka: Will other clients connect to this named queue?)
   config :exclusive, :validate => :boolean, :default => true
 
-  # Prefetch count. Number of messages to prefetch
+  # Using the prefetch_count option means that if ack is true, the server will
+  # only send the number of messages specified in the prefetch_count option
+  # to logstash and then the server will wait until logstash acknowledges
+  # a message prior to the server sending logstash more messages.  In practice,
+  # if ack is true, logstash acknowledges each message.  So increasing
+  # prefetch_count might not yield any practical benefit today.
+  # Must be 0 or a positive integer.
   config :prefetch_count, :validate => :number, :default => 1
 
-  # Enable message acknowledgement
+  # Enable message acknowledgement. The ack only matters if prefetch_count is
+  # more than 0.  Message acknowledgement improves reliablity but it reduces
+  # throughput since logstash needs to tell rabbitmq-server that logstash
+  # received the message.  Logstash will acknowledge only after it is able to
+  # process the message into a Logstash Event
   config :ack, :validate => :boolean, :default => true
 
   # Enable or disable debugging
@@ -123,6 +133,12 @@ class LogStash::Inputs::RabbitMQ < LogStash::Inputs::Threadable
       @rabbitmq_url << "@"
     end
     @rabbitmq_url += "#{@host}:#{@port}#{@vhost}/#{@queue}"
+
+    if @prefetch_count < 0
+      raise RuntimeError.new(
+        "Cannot specify prefetch_count less than 0"
+      )
+    end
   end # def register
 
   def run(queue)
@@ -131,12 +147,12 @@ class LogStash::Inputs::RabbitMQ < LogStash::Inputs::Threadable
       @bunny = Bunny.new(@rabbitmq_settings)
       return if terminating?
       @bunny.start
-      @bunny.qos({:prefetch_count => @prefetch_count})
+      @bunny.default_channel.prefetch(@prefetch_count)
 
       @arguments_hash = Hash[*@arguments]
 
       @bunnyqueue = @bunny.queue(@queue, {:durable => @durable, :auto_delete => @auto_delete, :exclusive => @exclusive, :arguments => @arguments_hash })
-      @bunnyqueue.bind(@exchange, :key => @key)
+      @bunnyqueue.bind(@exchange, :routing_key => @key)
 
       # need to get metadata from data
       @bunnyqueue.subscribe({:ack => @ack, :block => true}) do |delivery_info, metadata, data|
@@ -154,6 +170,15 @@ class LogStash::Inputs::RabbitMQ < LogStash::Inputs::Threadable
             end # headers_add.each do
           end # if !@headers_fields.empty?
           queue << e
+
+          # if these conditions are met, the server won't send any more
+          # messages until we specifically ack this message
+          # TODO(jkoppe): to improve throughput, we could ack less often
+          # but, I definitely want to get community buy-in before enabling
+          # one method or another.
+          if @ack and @prefetch_count > 0
+            @bunny.default_channel.ack(delivery_info[:delivery_tag])
+          end
         end # if e
       end # @bunnyqueue.subscribe do
 

lib/logstash/outputs/rabbitmq.rb

@@ -148,12 +148,12 @@ class LogStash::Outputs::RabbitMQ < LogStash::Outputs::Base
       if @bunnyexchange
         if @headers_add.empty?
           #tags2headers is empty, so we send the message normally
-          @logger.debug(["Publishing message", { :destination => to_s, :message => message, :key => key }])
-          @bunnyexchange.publish(message, :persistent => @persistent, :key => key)
+          @logger.debug(["Publishing message", { :destination => to_s, :message => message, :routing_key => key }])
+          @bunnyexchange.publish(message, :persistent => @persistent, :routing_key => key)
         else
           #publishing messages WITH headers, that are stored in "headers_add"
-          @logger.debug(["Publishing message", { :destination => to_s, :message => message, :key => key , :headers => @headers_add.inspect}])
-          @bunnyexchange.publish(message, :persistent => @persistent, :key => key, :headers => @headers_add)
+          @logger.debug(["Publishing message", { :destination => to_s, :message => message, :routing_key => key , :headers => @headers_add.inspect}])
+          @bunnyexchange.publish(message, :persistent => @persistent, :routing_key => key, :headers => @headers_add)
           
         end # if @headers2headers.empty?
       else