SHOW POOLS
A new pool entry is made for each couple of (database, user).
database
Database name.
user
User name.
cl_active
Client connections that are either linked to server connections or are idle with no queries waiting to be processed.
cl_waiting
Client connections that have sent queries but have not yet got a server connection.
[...]
Therefore it does not make much sense to report data with username=null
The docs says"
Therefore it does not make much sense to report data with
username=null