Comment 4 for bug 1756988

First, confirming config:

 - os-access-hostname is set to mysql-internal.maas
 - dns-ha is set to True
 - vips are not set

Check. The config looks sane based on documented usage.

...

Here are all of the charm-driven maas dns events:

rbeisner@rby:~/Downloads/juju-crashdump-ef4ff605-0aa3-490c-ab3b-56b835ca0b19⟫ find -type f -name unit-* | xargs grep "ocf:maas:dns" | pastebinit -a beisner
http://paste.ubuntu.com/p/x5K8t8fDgG/

...

A converged timeline looks like this:

2018-03-17 12:52:46 mysql-0 says: mysql-internal.maas is set to 10.244.40.241

2018-03-17 12:52:49 maas says: ip 10.244.40.241 linked to resource mysql-internal on zone maas

2018-03-17 12:52:49 maas says: ip 192.168.33.130 unlinked from resource mysql-internal on zone maas

2018-03-17 12:58:01 heat-1 says: heat-internal.maas is set to 192.168.33.158

2018-03-17 12:58:03 heat-1 says: heat-public.maas is set to 10.244.40.235

2018-03-17 13:05:55 mysql-1 says: Grant does NOT exist for host '192.168.33.158' on db 'heat'

2018-03-17 13:06:00 mysql-1 says: Grant exists for host '192.168.33.158' on db 'heat'

2018-03-17 13:08:08 The heat-1 unit traces with DEBUG shared-db-relation-changed 2018-03-17 13:08:08.085 148514 ERROR oslo_db.sqlalchemy.exc_filters InternalError: (1130, u"Host '10.244.40.235' is not allowed to connect to this MySQL server")

...

The percona cluster units never check or set a db grant for a 10.244 address, which confirms the error as reported:

rbeisner@rby:~/Downloads/juju-crashdump-ef4ff605-0aa3-490c-ab3b-56b835ca0b19⟫ find -type f -name unit-*mysql* | xargs grep "Grant.*heat.*" | pastebinit -a beisner
http://paste.ubuntu.com/p/4WMRZ7zdx4/