Fail to update OS::Neutron::Subnet resource

[Simon Pasquier]

Environment:
- Neutron Grizzly
- Heat Havana RC2

Given the following resource:

"demo_first_subnet": {
      "Type": "OS::Quantum::Subnet",
      "Properties": {
        "ip_version": 4,
        "network_id": {
          "Ref": "demo_first_subnet_network"
        },
        "cidr": "10.0.0.0/24",
        "dns_nameservers": [
          "10.197.217.62"
        ],
        "name": "demo_first_subnet"
      }
    }

I run a stack update with this modified template to add a DNS server:
"demo_first_subnet": {
      "Type": "OS::Quantum::Subnet",
      "Properties": {
        "ip_version": 4,
        "network_id": {
          "Ref": "demo_first_subnet_network"
        },
        "cidr": "10.0.0.0/24",
        "dns_nameservers": [
          "10.197.217.62",
          "10.197.217.66"
        ],
        "name": "demo_first_subnet"
      }
    }

The stack update will fail with "NeutronClientException: 400-{u'QuantumError': u'Invalid input for operation: Requested subnet with cidr: 10.0.0.0/24 for network: a283079c-72bf-4d4b-9944-f506e1b6f1ee overlaps with another subnet.'

There are 2 issues in fact:
- OS::Neutron::Subnet resource doesn't support updates for dns_nameservers while it should ('neutron subnet-update 8e578c1d-cd19-4cc4-b9b5-4e563d32addb --dns_nameservers list=true 10.197.217.62 10.197.217.66' works as expected)
- Since OS::Neutron::Subnet resource is not updatable, Heat tries to create the new subnet before deleting the old one but this fails because 2 subnets for the same tenant cannot overlap.

I haven't inspected the code in depth but there are probably other Neutron resources with similar issues.

[Steve Baker (steve-stevebaker)]

Unfortunately update without replacement has not yet been implemented for any of the neutron resources. I think this would be achievable by icehouse-1

[Steve Baker (steve-stevebaker)]

Partially addressed by the following committed changes:
https://review.openstack.org/#/c/55764/
https://review.openstack.org/#/c/55763/

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/55944

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/55765
Committed: http://github.com/openstack/heat/commit/721e588aebd765e4ff4326cc3a135b8cbfc8738d
Submitter: Jenkins
Branch: master

commit 721e588aebd765e4ff4326cc3a135b8cbfc8738d
Author: Steve Baker <email address hidden>
Date: Fri Nov 1 16:26:01 2013 +1300

    Implement update for neutron router resources

    This change allows any updatable properties to be updated
    on an existing router without replacement. Documentation
    is limited on what properties are updatable, so discovery
    was manual.

    Partial-Bug: #1241553
    Change-Id: Ia3b1885cee2f3440bb73724291d46d5af19962eb

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/55944
Committed: http://github.com/openstack/heat/commit/8e23e6819d513c5d4e4a965c66497f4b0834df43
Submitter: Jenkins
Branch: master

commit 8e23e6819d513c5d4e4a965c66497f4b0834df43
Author: Steve Baker <email address hidden>
Date: Tue Nov 12 09:47:35 2013 +1300

    Implement update for neutron port resources

    This change allows any updatable properties to be updated
    on an existing port without replacement. Documentation
    is limited on what properties are updatable, so discovery
    was manual. Unlike other neutron resources, port name is not
    updateable without replacement.

    Change-Id: I7845702e14baab595363d57bcf6128e45ffdd789
    Closes-Bug: #1241553

[Steve Baker (steve-stevebaker)]

I think this is too feature-y to consider for havana backport