Symptoms

K2 is still sending emails to the old users
 

Diagnoses

My workflow has a task in which the destination users are picked from SharePoint group, which allows the users to be changed at group level.
Even though old users are replaced by new ones, K2 is still sending the task email to the old users not the new one.

I am using the Advanced property-->Creating 1 slot--->Resolving all roles to users and then choosing the group.
 

Resolution

Users and group memberships are cached in K2 "Identity Service" that will usually expire and refresh according to default settings (default 1 hours +- 10 minutes) and can be modified if necessary (a K2 server service restart is necessary if doing so). Please see attached documentation:

http://help.k2.com/onlinehelp/k2blackpearl/icg/4.6.9/webframe.html_tweaking_identity_cache_performance_for_the_k2_server.html

If you would like to force the membership refresh for a group right away:

1. Please execute the attached "ForceIdentityServiceRefreshv2.zip" tool. See detail in "ExpireGroupMembership.png" to expire this group membership.

2. Then use the "Smartobject Service Tester Tool > All Smartobjects > UmUser > Get Group Users method" to refresh the membership (see attached "UMUserGetGroupUsers.png". Please execute this method until you see the membership updated. The Smartobject Service Tester Tool is usually located at "C:Program Files(x86)K2 blackpearlBin".

3. New process instances started will now use the updated group membership.

Customer resolved the issue.