This is related to modifications done for RFE 4343.

Sometimes a message like this appears in the logs:

"Monitor data of remote servers are missing due to an error in the 
retrieval process. Potentially a server is too slow to provide its 
monitoring data over the protocol"

This seems to be introduced by the monitoring publisher thread which may 
call the ReplicationServerDomain.completeMonitorData method at the same 
time a MonitoringRequest message is being treated and is also in the 
same method.

These 2 threads are concurrently running the 
ReplicationServerDomain.completeMonitorData method as one of the thread 
wants to execute wrkMonitorData.completeComputing() which is outside of 
the syncronized section, the other thread may reset wrkMonitorData to 
null just before and this leads to a NPE. So another RS waiting for the 
monitor response will never receive it and display the annoying message.

The fix is to move the wrkMonitorData.completeComputing() call into the 
synchronized section.