Java Client is logging at ERROR
during connection. This is due to the client executing a call to DynamicSaslRegistrar#registerSaslProviders twice: once from AMQConnectionDelegate_0_10 and once from ClientConnectionDelegate#createSaslClient/CallbackHandlerRegistry
The error caused by the duplicate call is harmless and can be safely ignored.
The call to DynamicSaslRegistrar#registerSaslProviders should be made earlier, possibly from AMQConnection or its factory.