Neutron port detach isn't detected by nova event handler

on interface-attach, device_id identifies the server

{
  "event_type": "port.update.end",
  "payload": {
    "port": {
      "allowed_address_pairs": [],
      "extra_dhcp_opts": [],
      "updated_at": "2016-04-06T17:38:09",
      "device_owner": "compute:None",
      "port_security_enabled": true,
      "binding:profile": {},
      "fixed_ips": [
        {
          "subnet_id": "e89b3879-db18-4c9d-a2b5-9a985f0bd512",
          "ip_address": "172.40.0.4"
        },
        {
          "subnet_id": "44064101-3f26-4eae-ab0e-2c9e6751f849",
          "ip_address": "fd4f:2ae3:e98a:0:f816:3eff:fe2e:2028"
        }
      ],
      "id": "ee486fc1-0919-4109-9990-a2f21b25fec7",
      "security_groups": [
        "9790d25c-aea7-4342-b4ef-5f0f7cb657bd"
      ],
      "binding:vif_details": {
        "port_filter": true,
        "ovs_hybrid_plug": true
      },
      "binding:vif_type": "ovs",
      "mac_address": "fa:16:3e:2e:20:28",
      "status": "DOWN",
      "binding:host_id": "devstack",
      "description": "",
      "device_id": "e861a26d-7d54-4f6a-8511-46eeb3dd4abe",
      "name": "attaching-port",
      "admin_state_up": true,
      "network_id": "910cc348-b4f2-4ee3-b131-27829ab59984",
      "dns_name": "octo-1",
      "created_at": "2016-04-01T17:47:16",
      "binding:vnic_type": "normal",
      "tenant_id": "3307049f95b7408c95d6e84483fc995a"
    }
  }
  # <SNIP>
}

On detach, not so much:

{
  "event_type": "port.update.end",
  "payload": {
    "port": {
      "allowed_address_pairs": [],
      "extra_dhcp_opts": [],
      "updated_at": "2016-04-06T17:40:05",
      "device_owner": "",
      "port_security_enabled": true,
      "binding:profile": {},
      "fixed_ips": [
        {
          "subnet_id": "e89b3879-db18-4c9d-a2b5-9a985f0bd512",
          "ip_address": "172.40.0.4"
        },
        {
          "subnet_id": "44064101-3f26-4eae-ab0e-2c9e6751f849",
          "ip_address": "fd4f:2ae3:e98a:0:f816:3eff:fe2e:2028"
        }
      ],
      "id": "ee486fc1-0919-4109-9990-a2f21b25fec7",
      "security_groups": [
        "9790d25c-aea7-4342-b4ef-5f0f7cb657bd"
      ],
      "binding:vif_details": {},
      "binding:vif_type": "unbound",
      "mac_address": "fa:16:3e:2e:20:28",
      "status": "DOWN",
      "binding:host_id": "",
      "description": "",
      "device_id": "",
      "name": "attaching-port",
      "admin_state_up": true,
      "network_id": "910cc348-b4f2-4ee3-b131-27829ab59984",
      "dns_name": "octo-1",
      "created_at": "2016-04-01T17:47:16",
      "binding:vnic_type": "normal",
      "tenant_id": "3307049f95b7408c95d6e84483fc995a"
    }
  }
  # SNIP
}

Running a query against servers in e-s seems like something to try to avoid; it will rely on the search index being up to date (i.e. although a document may have been indexed it's not necessarily visible to search yet versus retrieval by id). I don't see a cleaner option though. Ideally nova would send out a notification as it does for volume attach.

I'm inclined to mark this as a wishlist item for nova, since as you concur, showing a detached interface with an empty device_id seems to be the reasonable thing to do. What you are suggesting seems to be that nova should generate notification events on interface attach and detach. Feel free to correct me if I missed your point.

Hi Fahri,

Yeah, having thought about this some more, I do think nova should generate notifications on interface attach/detach, and maybe that should be a separate ticket. Since it does the same thing for volume events it wouldn't be unusual.

Since neutron sends a port.update notification that only includes the current state, it's not possible to determine the reason for the update or what the port was previously attached to in the case of a detach; arguably the neutron events could be more explicit but that's a discussion i can have with the neutron team.

Hello Steve,

I think it is also reasonable to expect nova to create such a notification, since as far as I can tell; e.g. for a port unbind operation, nova checks whether the device ID was successfully cleared, so that could be a suitable place for firing up a notification.

Also, I'm not sure whether you are aware or not, but the nova team has a proposal for eliminating bug reports which may be deemed as wishlist/enhancement items, requiring those requests to be in the form of blueprints. So while I think that you have a perfectly good proposal here, there is a chance that it might be neglected in nova's bug database, mostly by being shadowed by other items of higher priority.

However, I'd say having such a report for nova is certainly beneficial for achieving alignment with the Searchlight project and keeping track of the progress, though I'm far from an expert on this issue.

Ok - I'm happy to re-file this as a blueprint. Thanks for the feedback; I'll include your comments in the BP.

Ok, I'll keep an eye on incoming blueprints and when you get around to creating the blueprint I'll see if there is a way I can contribute. Please feel free to link the blueprint here for better trackability and visibility. Thank you.

https://blueprints.launchpad.net/nova/+spec/interface-notifications

Thanks Fahri!

Thank you for the blueprint, don't think a spec would be required for this case, since the corresponding change would be small. However, for best results you may want to have some nova people take a look and share their opinion, so that the implementation would have a point of reference.