refactor: refactors message dequeueing (#2810)

app/lib/message_dequeuer/initial_processor.rb

@@ -0,0 +1,62 @@
+# frozen_string_literal: true
+
+module MessageDequeuer
+  class InitialProcessor < Base
+
+    attr_accessor :send_result
+
+    def process
+      logger.tagged(original_queued_message: @queued_message.id) do
+        logger.info "starting message unqueue"
+        begin
+          catch_stops do
+            check_message_exists
+            check_message_is_ready
+            find_other_messages_for_batch
+
+            # Process the original message and then all of those
+            # found for batching.
+            process_message(@queued_message)
+            @other_messages.each { |message| process_message(message) }
+          end
+        ensure
+          @state.finished
+        end
+        logger.info "finished message unqueue"
+      end
+    end
+
+    private
+
+    def check_message_exists
+      @queued_message.message
+    rescue Postal::MessageDB::Message::NotFound
+      log "unqueue because backend message has been removed."
+      remove_from_queue
+      stop_processing
+    end
+
+    def check_message_is_ready
+      return if @queued_message.ready?
+
+      log "skipping because message isn't ready for processing"
+      @queued_message.unlock
+      stop_processing
+    end
+
+    def find_other_messages_for_batch
+      @other_messages = @queued_message.batchable_messages(100)
+      log "found #{@other_messages.size} associated messages to process at the same time", batch_key: @queued_message.batch_key
+    rescue StandardError
+      @queued_message.unlock
+      raise
+    end
+
+    def process_message(queued_message)
+      logger.tagged(queued_message: queued_message.id) do
+        SingleMessageProcessor.process(queued_message, logger: @logger, state: @state)
+      end
+    end
+
+  end
+end