Configure consumer tag names/prefixes

README.md

@@ -358,6 +358,11 @@ In order from lowest to highest precedence:
 
 ### Generated list of configuration options
 
+Generate with
+
+0. `yard doc lib/hutch/config.rb`
+0. Copy the _Configuration_ section from `doc/Hutch/Config.html` here, with the anchor tags stripped.
+
 <table border="1" class="settings" style="overflow:visible;">
   <thead>
     <tr>
@@ -595,6 +600,15 @@ In order from lowest to highest precedence:
       <td><p>Should Bunny's consumer work pool threads abort on exception.</p>
 </td>
     </tr>
+
+    <tr>
+      <td><tt>consumer_tag_prefix</tt></td>
+      <td>hutch</td>
+      <td>String</td>
+      <td><tt>HUTCH_CONSUMER_TAG_PREFIX</tt></td>
+      <td><p>Prefix displayed on the consumers tags.</p>
+</td>
+    </tr>
 
   </tbody>
 </table>

lib/hutch/config.rb

@@ -130,6 +130,9 @@ def self.boolean_setting(name, default_value)
     # The option is ignored on JRuby.
     boolean_setting :consumer_pool_abort_on_exception, false
 
+    # Prefix displayed on the consumers tags.
+    string_setting :consumer_tag_prefix, 'hutch'
+
     # Set of all setting keys
     ALL_KEYS = @boolean_keys + @number_keys + @string_keys
 

lib/hutch/worker.rb

@@ -4,6 +4,7 @@
 require 'hutch/acknowledgements/nack_on_all_failures'
 require 'hutch/waiter'
 require 'carrot-top'
+require 'securerandom'
 
 module Hutch
   class Worker
@@ -44,7 +45,7 @@ def setup_queue(consumer)
       queue = @broker.queue(consumer.get_queue_name, consumer.get_arguments)
       @broker.bind_queue(queue, consumer.routing_keys)
 
-      queue.subscribe(manual_ack: true) do |*args|
+      queue.subscribe(consumer_tag: unique_consumer_tag, manual_ack: true) do |*args|
         delivery_info, properties, payload = Hutch::Adapter.decode_message(*args)
         handle_message(consumer, delivery_info, properties, payload)
       end
@@ -103,5 +104,13 @@ def error_acknowledgements
     private
 
     attr_accessor :setup_procs
+
+    def unique_consumer_tag
+      prefix = Hutch::Config[:consumer_tag_prefix]
+      unique_part = SecureRandom.uuid
+      "#{prefix}-#{unique_part}".tap do |tag|
+        raise "Tag must be 255 bytes long at most, current one is #{tag.bytesize} ('#{tag}')" if tag.bytesize > 255
+      end
+    end
   end
 end

spec/hutch/worker_spec.rb

@@ -45,9 +45,27 @@
     end
 
     it 'sets up a subscription' do
-      expect(queue).to receive(:subscribe).with(manual_ack: true)
+      expect(queue).to receive(:subscribe).with(consumer_tag: %r(^hutch\-.{36}$), manual_ack: true)
       worker.setup_queue(consumer)
     end
+
+    context 'with a configured consumer tag prefix' do
+      before { Hutch::Config.set(:consumer_tag_prefix, 'appname') }
+
+      it 'sets up a subscription with the configured tag prefix' do
+        expect(queue).to receive(:subscribe).with(consumer_tag: %r(^appname\-.{36}$), manual_ack: true)
+        worker.setup_queue(consumer)
+      end
+    end
+
+    context 'with a configured consumer tag prefix that is too long' do
+      let(:maximum_size) { 255 - SecureRandom.uuid.size - 1 }
+      before { Hutch::Config.set(:consumer_tag_prefix, 'a'.*(maximum_size + 1)) }
+
+      it 'raises an error' do
+        expect { worker.setup_queue(consumer) }.to raise_error(/Tag must be 255 bytes long at most/)
+      end
+    end
   end
 
   describe '#handle_message' do