If anyone see in Node that Disk Journal utilization is more than 100% and due to which there are millions of messages are flooded and cannot be processed. So you cannot process the unprocessed message in running Graylog server . You need to increase the graylog journal size from 5GB to 10 GB and restart the server. Now you will see though incoming messages are too high but gradually all messages will be processed as journal Size is now increased and it can keep more messages until all the unprocessed messages can be processed and write to Elastic Search .
Please let me know if you have any other suggestion.