Comment 41 for bug 1323658

I guest I have got this issue on a real running cluster.

I have made some investigation, to find a difference between instance that loose their network interfaces after hard reboot, and those that doesn't.
When as say 'loose their network interfaces', I means the network device is no more present into the guest and the libvirt configuration.

On a bugged instance:

We can see that networks is empty in 'nova list', but the interface is still attached:

    # nova list --name XXXXXXXXXXXX
    +--------------------------------------+---------------------+--------+------------+-------------+----------+
    | ID | Name | Status | Task State | Power State | Networks |
    +--------------------------------------+---------------------+--------+------------+-------------+----------+
    | 940be621-97a9-409a-8c31-7c0c9c8afbfd | XXXXXX | ACTIVE | - | Running | |
    +--------------------------------------+---------------------+--------+------------+-------------+----------+
    # nova interface-list 940be621-97a9-409a-8c31-7c0c9c8afbfd
    +------------+--------------------------------------+--------------------------------------+---------------------------------------+-------------------+
    | Port State | Port ID | Net ID | IP addresses | MAC Addr |
    +------------+--------------------------------------+--------------------------------------+---------------------------------------+-------------------+
    | ACTIVE | cdfb0e9f-d0cd-4ca7-9954-0fce25680905 | 07487477-8cbd-4d2a-b549-713a964ddb51 | XXXXXXXXXXXXXXXXX | fa:16:3e:fc:78:a3 |
    +------------+--------------------------------------+--------------------------------------+---------------------------------------+-------------------+

So I have looked into the db and it seems that something have emptied the columns "instance_info_caches.network_info" of some of my instances:

    mysql> select * from instance_info_caches where id = 174;
    +---------------------+---------------------+------------+-----+--------------+--------------------------------------+---------+
    | created_at | updated_at | deleted_at | id | network_info | instance_uuid | deleted |
    +---------------------+---------------------+------------+-----+--------------+--------------------------------------+---------+
    | 2014-09-22 13:59:11 | 2014-10-20 05:39:48 | NULL | 174 | [] | 940be621-97a9-409a-8c31-7c0c9c8afbfd | 0 |
    +---------------------+---------------------+------------+-----+--------------+--------------------------------------+---------+
    1 row in set (0.00 sec)