Comment 2 for bug 1402795

Detail description of the defect.

Token flush does
     Select expiry date
     delete based on expiry date

Select will take READ lock and delete will take exclusive ROW lock in mysql. So if the same operation is running on all the controller nodes, then other nodes will be unnecessaily waiting for the lock since all of them expects LOCK for the same rows.

Easy way to figure to check is, to grep for transaction read time out message in all the controller nodes. You will always see read time out in all the controller node except one for a particular run