By removing an aggregate, the associated metadata remains in the database, and upon re-creation of the same aggregate, the old metadata is returned from the previously deleted aggregate.
If you have an aggregate with some metadata:
stack@DevStackOSDomU:~/devstack$ nova aggregate-details 1
+----+---------------------+-------------------+-------+...
| Id | Name | Availability Zone | Hosts |
+----+---------------------+-------------------+-------+...
| 1 | my_livemigrate_pool | nova | [] |
+----+---------------------+-------------------+-------+...
...-----------------------------------------------------------------...
Metadata
...-----------------------------------------------------------------...
{u'master_compute': u'DevStackOSDomU', u'operational_state': u'crea
...-----------------------------------------------------------------...
And you remove that aggregate:
stack@DevStackOSDomU:~/devstack$ nova aggregate-delete 1
Aggregate 1 has been successfully deleted.
And re-create with the same name:
stack@DevStackOSDomU:~/devstack$ nova aggregate-create my_livemigrate_pool nova
+----+---------------------+-------------------+-------+----------+
| Id | Name | Availability Zone | Hosts | Metadata |
+----+---------------------+-------------------+-------+----------+
| 1 | my_livemigrate_pool | nova | | |
+----+---------------------+-------------------+-------+----------+
It is saying, that metadata is empty,
Whereas querying the details shows that the metadata persists:
stack@DevStackOSDomU:~/devstack$ nova aggregate-details 1
+----+---------------------+-------------------+-------+...
| Id | Name | Availability Zone | Hosts |
+----+---------------------+-------------------+-------+...
| 1 | my_livemigrate_pool | nova | [] |
+----+---------------------+-------------------+-------+...
...-----------------------------------------------------------------...
Metadata
...-----------------------------------------------------------------...
{u'master_compute': u'DevStackOSDomU', u'operational_state': u'crea
...-----------------------------------------------------------------...
This is caused by two things:
1) when adding an aggregate that has the same name as a deleted one. The deleted aggregate is undeleted.
2) When deleting an aggregate, only the Aggregate table row is marked as deleted and not the AggregateMetadata and AggregateHost rows.