Connection get() {
      if (connection == null) {
        synchronized (this) {
          if (connection == null) {
            connection = compute();
          }
        }
      }
      return connection;
    }
Lazy creates a connection and a queue before starting consumers
zipkin-collector/rabbitmq/src/main/java/zipkin2/collector/rabbitmq/RabbitMQCollector.java