add okcomputer check for expected RabbitMQ queues

suggested in #2291

config/initializers/okcomputer.rb

@@ -68,6 +68,37 @@ def check
  OkComputer::Registry.register "feature-#{name}-sdr2objects", DirectoryExistsCheck.new(sdrobjects_location, Settings.minimum_subfolder_count)
 end
 
+# Check that RabbitMQ queues exist
+class RabbitQueueExistsCheck < OkComputer::Check
+ attr_reader :queue_names, :conn
+
+ def initialize(queue_names)
+ @queue_names = Array(queue_names)
+ @conn = Bunny.new(hostname: Settings.rabbitmq.hostname,
+ vhost: Settings.rabbitmq.vhost,
+ username: Settings.rabbitmq.username,
+ password: Settings.rabbitmq.password)
+ super()
+ end
+
+ def check
+ conn.start
+ status = conn.status
+ missing_queue_names = queue_names.reject { |queue_name| conn.queue_exists?(queue_name) }
+ if missing_queue_names.empty?
+ mark_message "'#{queue_names.join(', ')}' exists, connection status: #{status}"
+ else
+ mark_message "'#{missing_queue_names.join(', ')}' does not exist"
+ mark_failure
+ end
+ conn.close
+ rescue StandardError => e
+ mark_message "Error: '#{e}'"
+ mark_failure
+ end
+end
+OkComputer::Registry.register 'rabbit-queues', RabbitQueueExistsCheck.new('dsa.create-event')
+
 OkComputer::Registry.register 'ruby_version', OkComputer::RubyVersionCheck.new
 
 # ------------------------------------------------------------------------------

spec/config/okcomputer_spec.rb

@@ -37,4 +37,35 @@
  expect(described_class.new('i-do-not-exist')).not_to be_successful
  end
  end
+
+ describe RabbitQueueExistsCheck do
+ let(:bunny_conn) { instance_double(Bunny::Session) }
+ let(:queue_name1) { 'foo.first_queue' }
+ let(:queue_name2) { 'foo.second_queue' }
+
+ before do
+ allow(bunny_conn).to receive_messages(start: bunny_conn, status: :open, close: true)
+ allow(bunny_conn).to receive(:queue_exists?).with(queue_name1).and_return(queue_exists1)
+ allow(bunny_conn).to receive(:queue_exists?).with(queue_name2).and_return(queue_exists2)
+ allow(Bunny).to receive(:new).and_return(bunny_conn)
+ end
+
+ context 'when the expected queues are present' do
+ let(:queue_exists1) { true }
+ let(:queue_exists2) { true }
+
+ it 'succeeds if the expected queue exists' do
+ expect(described_class.new([queue_name1, queue_name2])).to be_successful
+ end
+ end
+
+ context 'when a queue is missing' do
+ let(:queue_exists1) { true }
+ let(:queue_exists2) { false }
+
+ it 'succeeds if the expected queue exists' do
+ expect(described_class.new([queue_name1, queue_name2])).not_to be_successful
+ end
+ end
+ end
 end