Warning: java.util.ConcurrentModificationException



This Knowledgebase article provides details about this particular error message that can be seen in the NFLog files:


More Information


Error message:

[Commands](com.neverfail.manager.NFCmdDispatcher) - Command GetMultiReadablePropertyValues failed by throwing java.util.ConcurrentModificationException


This exception is thrown by the Java engine on which Heartbeat's functionality is based. Here you can see the description of the ConcurrentModificationException from java.util.

With Neverfail, the ConcurrentModificationException is thrown when serialising the result object when firing a CommandComplete event.

As the FSM events are used to render the GUI, then this exception may starve the GUI of FSM information. Therefore if the last piece of information the GUI recieved set the gui current file to nothing (as it does at certain times) then this may be why it remains blank. Alternatively if the last peice of information showed a file at a particular percentage then it would appear that the server was still working on the file.

Therefore, the effect of this error is that the File System remains blank and unavailable on the data tab (the Full System Check is not completed).


This exception can be fixed by closing all the Management Clients (GUI) whether local, remote or local via RDP while the full system check is in progress (or for as long as this is approximated to be in progress). To verify the full system check progress, the GUI should be started only for short periods of time and closed if the task is not completed.

Recovery Action

This exception is fixed in builds 5.0.3 and later.

Applies To

Builds V5.0.2 and earlier

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