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This is expected behavior introduced in icehouse.
Once there is no space for increasing IP, whole range will be recalculated and unused IPs will be reclaimed.
This was done to not to recalculate it every time ip is de-allocated, it's a kind of optimization.

The link for the patch :https://review.openstack.org/58017

Thanks.
-chen

From: Li, Chen
Sent: Thursday, June 26, 2014 1:06 PM
To: openstack at lists.openstack.org
Subject: [Neutron] ipavailabilityranges is narrowing down

Hi list,

I'm working under CentOS + icehouse.

I have created a private network with a subnet:

neutron net-list
+--------------------------------------+------+-----------------------------------------------------+
| id                                   | name | subnets                                             |
+--------------------------------------+------+-----------------------------------------------------+
| c4f961d1-ac22-47d7-8edd-0829420c35cc | net  | b488f9c7-f4e0-4bb5-a648-b5da343fb138 172.16.24.0/24 |
+--------------------------------------+------+-----------------------------------------------------+


neutron subnet-list
+--------------------------------------+-------------+----------------+---------------------------------------------------+
| id                                   | name        | cidr           | allocation_pools                                  |
+--------------------------------------+-------------+----------------+---------------------------------------------------+
| b488f9c7-f4e0-4bb5-a648-b5da343fb138 | flat_subnet | 172.16.24.0/24 | {"start": "172.16.24.10", "end": "172.16.24.253"} |
+--------------------------------------+-------------+----------------+---------------------------------------------------+

Well, everything works fine, I can create instances with the network, and can connected to instances as well.

But, then I noticed a small issue:
Every time, when I create a new instance, the IP address the instances get keeps increasing.
For example, I create instance A, it's IP is 172.16.24.12.
Then I delete instance A, then create instance B, instance B's IP would be 172.16.24.13.
When I working under Havana, instance B would get 172.16.24.12.

Then I went to database and did a simple check:

mysql> select * from ipallocationpools;
+--------------------------------------+--------------------------------------+--------------+---------------+
| id                                   | subnet_id                            | first_ip     | last_ip       |
+--------------------------------------+--------------------------------------+--------------+---------------+
| d84f82c7-3815-4b61-9ba7-32522656a8d3 | b488f9c7-f4e0-4bb5-a648-b5da343fb138 | 172.16.24.10 | 172.16.24.253 |
+--------------------------------------+--------------------------------------+--------------+---------------+
1 row in set (0.00 sec)

mysql> select * from ipallocations;
+--------------------------------------+--------------+--------------------------------------+--------------------------------------+
| port_id                              | ip_address   | subnet_id                            | network_id                           |
+--------------------------------------+--------------+--------------------------------------+--------------------------------------+
| 331461c5-7f9f-484d-8136-f7c2ea044d2c | 172.16.24.11 | b488f9c7-f4e0-4bb5-a648-b5da343fb138 | c4f961d1-ac22-47d7-8edd-0829420c35cc |
| 4b070d15-e96c-44a0-a3eb-2086066ed580 | 172.16.24.43 | b488f9c7-f4e0-4bb5-a648-b5da343fb138 | c4f961d1-ac22-47d7-8edd-0829420c35cc |
+--------------------------------------+--------------+--------------------------------------+--------------------------------------+
2 rows in set (0.00 sec)

mysql> select * from ipavailabilityranges;
+--------------------------------------+--------------+---------------+
| allocation_pool_id                   | first_ip     | last_ip       |
+--------------------------------------+--------------+---------------+
| d84f82c7-3815-4b61-9ba7-32522656a8d3 | 172.16.24.44 | 172.16.24.253 |
+--------------------------------------+--------------+---------------+
1 row in set (0.00 sec)

As you can see,  ipavailabilityranges is narrowing down.
Shouldn't it include 2 parts?   172.16.24.10 &   172.16.24.12-172.17.24.41 &  172.16.24.44 - 172.16.24.253.
Because only 2 IPs are actually using.

I'm worried if I created more instances, even I deleted them all at end, there would still be no IP available at all.

Anyone know why this is happening ??
Is this a real issue ?

Thanks.
-chen




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