When I misuse a secure hbase client to access a secure-disabled hbase server, I found the client will hang. The reason is that client will firstly invoke rpc method "getProtocolVersion", and the response from a secure-disabled server won't contain necessary fields processed by SecureClient. SecureClient will process the response as follows : (from SecureClient.receiveResponse()):
As the above code, SecureClient need to read 'state' field from response. If the response is from a secure-disabled server, there will no 'state' field in response and SecureClient will get an illegal 'state', then the call will be removed from cached calls without notifying waiting thread. This will make the invoker waiting all the time. Although we should not use secure client to access secure-disabled server, users might encounter this situation because of misusing or error configuration. If the client will hang in this situation, users might not know the error quickly. Maybe, it is better to report an error in this situation so that users will know what happens quickly.