Symptoms

K2 host server logs are flooded with the following error:

"Error","General","0","ErrorMessage","1","0 SharePointRoleProvider.GetGroups: System.Reflection.TargetInvocationException: An unexpected failure was encountered when contacting SharePoint to get information from the group provider SPCsomClient: An unexpected error occurred (Too Many Requests). ---> System.Net.WebException: The remote server returned an error: (429) Too Many Requests.
 

Diagnoses

This issue can be caused by congestion on SQL Server side leading to slowness for SharePoint (but no errors logged on SharePoint Side) and aforementioned errors being logged by K2.

In such cases it is recommended to move K2 DB to dedicated SQL service instance (and ensure that it doesn't coexist on the same instance with SharePoint databases).
 

Resolution

Move K2 DB to dedicated SQL Server service instance (and ensure that it doesn't coexist on the same instance with SharePoint data bases). You should no longer receive error "429 - Too Many Requests" after this change.