lack of debug info for troubleshooting

When a image is created/updated/deleted, there isn't enough **debug** info in log file (like /var/log/glance/api.log). Adding some debug log will be helpful for users to trace the update history.
Like this:
Initial value ---> update 1 ---> update 2 ---> update 3 ---> delete.

# cat /etc/glance/glance-api.conf |grep ^debug
debug=True
#glance image-create --file /root/a.img --name testtest --container-format bare --disk-format qcow2
+------------------+--------------------------------------+
| Property | Value |
+------------------+--------------------------------------+
| checksum | 50bdc35edb03a38d91b1b071afb20a3c |
| container_format | bare |
| created_at | 2016-01-26T08:12:12Z |
| disk_format | qcow2 |
| id | 0e69fd8d-17bf-4a39-b480-71c2ee4c156b |
| min_disk | 0 |
| min_ram | 0 |
| name | testtest |
| owner | 5da2e9904c72482bba3bce0d64c809eb |
| protected | False |
| size | 9761280 |
| status | active |
| tags | [] |
| updated_at | 2016-01-26T08:12:13Z |
| virtual_size | None |
| visibility | private |
+------------------+--------------------------------------+
# grep "testtest" /var/log/glance/* -r ####Nothing returned here.
# glance image-update 0e69fd8d-17bf-4a39-b480-71c2ee4c156b --min-disk 54321
+------------------+--------------------------------------+
| Property | Value |
+------------------+--------------------------------------+
| checksum | 50bdc35edb03a38d91b1b071afb20a3c |
| container_format | bare |
| created_at | 2016-01-26T08:12:12Z |
| disk_format | qcow2 |
| id | 0e69fd8d-17bf-4a39-b480-71c2ee4c156b |
| min_disk | 54321 |
| min_ram | 0 |
| name | testtest |
| owner | 5da2e9904c72482bba3bce0d64c809eb |
| protected | False |
| size | 9761280 |
| status | active |
| tags | [] |
| updated_at | 2016-01-26T08:26:09Z |
| virtual_size | None |
| visibility | private |
+------------------+--------------------------------------+
# grep "54321" /var/log/glance/* -r ####Nothing returned here.