Symptoms

 Windows Event Viewer is flooded with this message:

"The User Manager 127.0.0.1 returned an empty queue."

This issue seems to be related related with K2 roles.

1. How to check the role dependicies when we cannot delete some roles?
2. "Server.DestQueue" table in K2 database shows some entries for users (NOT roles) with "interval" 5 seconds.
 

Diagnoses

This issue occurs whenever you have a role or an active directory group that has only one user that is not active or has resigned. I.e. each role and gruop have to contain at least one valid active user.
 

Resolution

This issue occurs whenever you have a role or an active directory group that has only one user that is not active or has resigned.

Inside of K2 database DestQueue table contains a mapping between processes and roles and it would not break the platform (current tasks assignment, existing destination rules, etc.) so you can try deleting the suspicious "user" records from the K2HostServer.DestQueue table to see if it resolves the “empty queue”. As a way to describe this issue K2 is considering those accounts as roles, and tries to “resolve” them to users.

Be sure to backup your K2 database before attempting any direct modification on it and in case of any doubts contact K2 supports.