Symptoms

When running the script for migrating the external memberships in admin/migrate-external-memberships.action, it fails.

The following appears in the atlassian-confluence.log:

2013-11-09 23:46:01,042 INFO [Long running task: Migrate External Memberships] [atlassian.crowd.directory.DelegatedAuthenticationDirectory] importMembership Imported user "Michael XYZ"'s membership of remote group "Group Name" to directory "Delegated Authentication Directory".
....
2013-11-09 23:46:01,167 ERROR [Long running task: Migrate External Memberships] [sf.hibernate.util.JDBCExceptionReporter] logExceptions Violation of UNIQUE KEY constraint 'cwd_unique_membership'. Cannot insert duplicate key in object 'dbo.cwd_membership'.

Cause

There are two different entities in LDAP are found with the same value for that attribute (CN). There is a feature request for this:  CONF-23213 - Getting issue details... STATUS

Workaround

1. Change the Group Search Filter in the User Directory Configuration so that it excludes the offending group. Example:

   (&(objectclass=groupOfNames)(!(CN=Group Name)))

2. Perform the migration again