Don't boot async subscribers in publisher mode.

Author: TreyE

.github/workflows/rspec.yml

@@ -35,4 +35,4 @@ jobs:
 #          bundle exec rubocop
       - name: Run rspec
         run: |
-          bundle exec rspec
+          ES_HOSTING_MODE=listener bundle exec rspec

lib/event_source/configure.rb

@@ -4,6 +4,7 @@
 require_relative "configure/servers"
 require_relative "configure/contracts"
 require_relative "configure/operations"
+require_relative "configure/mode"
 require_relative "configure/config"
 
 module EventSource

lib/event_source/configure/config.rb

@@ -26,6 +26,10 @@ def server_key=(value)
         @server_key = value&.to_sym
       end
 
+      def mode
+        @mode ||= ::EventSource::Configure::Mode.parse(ENV['ES_HOSTING_MODE'])
+      end
+
       attr_writer :async_api_schemas
 
       def servers

lib/event_source/configure/mode.rb

@@ -0,0 +1,34 @@
+# frozen_string_literal: true
+
+module EventSource
+  module Configure
+    # Server boot mode.  Used for performance and configuration settings.
+    class Mode
+
+      attr_reader :value
+
+      def initialize(val)
+        @value = val
+      end
+
+      def listener?
+        @value == :listener
+      end
+
+      def publisher?
+        @value == :publisher
+      end
+
+      def self.publisher
+        self.new(:publisher)
+      end
+
+      def self.parse(mode_string)
+        return publisher if mode_string.blank?
+        mode_sym = mode_string.to_sym
+        raise ::EventSource::Error::InvalidModeError, "\"#{mode_string}\" is an invalid mode. Must be empty, null, \"publisher\", or \"listener\"." if ![:publisher, :listener].include?(mode_sym)
+        self.new(mode_string.to_sym)
+      end
+    end
+  end
+end

lib/event_source/error.rb

@@ -21,6 +21,7 @@ class Error < StandardError
     ConstantNotDefined = Class.new(Error)
     ContractNotFound = Class.new(Error)
     EventNameUndefined = Class.new(Error)
+    InvalidModeError = Class.new(Error)
     FileAccessError = Class.new(Error)
     InvalidChannelsResourceError = Class.new(Error)
     PublisherAlreadyRegisteredError = Class.new(Error)

lib/event_source/protocols/amqp/bunny_queue_proxy.rb

@@ -73,6 +73,12 @@ def subscribe(subscriber_klass, bindings)
 
           @channel_proxy.subject.prefetch(prefetch)
 
+          # Do not spawn consumers in the 'publisher' mode
+          unless ::EventSource.config.mode.listener?
+            logger.debug "In publisher mode, not booting subscription"
+            return
+          end
+
           if options[:block]
             spawn_thread(options) { add_consumer(subscriber_klass, options) }
           else