Inconsistent notifications after subnet update

[Ilia Abashin]

Description
===========

When I use horizon UI to update name of an existing subnet (through "Edit Subnet" dialog), the relevant message that gets posted to nova message queue (RabbitMQ) is inconsistent in both "event_type" field and structure in general.

Steps to reproduce
==================
Prerequisite: Project should contain a network.

In Horizon UI:
1. In sidebar go to Project -> Network -> Networks.
2. In Subnets list click "Create subnet", fill the details and bind it to an existing network, click Next -> Create.
3. On networks screen click "Edit Subnet" button next to newly created subnet.
4. Change name to a new value, click Next -> Save.
Repeat steps 3-4 at least 3 times (preferably, each time use a previously unused name).

For "Expected/actual result" sections I'll refer to the subnet as "test-subnet". The sequence of updated names is the following:
"test-subnet" -> "test-subnet1" -> "test-subnet2" -> "test-subnet3" -> "test-subnet4" -> "test-subnet5" -> "test-subnet6"

Expected result
===============

For each update a message is posted to RabbitMQ of the following structure (only important fields specified):

{
  "event_type": "subnet.update.end",
  "payload": {
    "subnet": {
      "id": uuid of subnet,
      "name": updated subnet name
    }
  }
}

Actual result
=============
For these consequential updates the pattern observed is the following:

1) "test-subnet" -> "test-subnet1"
{
  "event_type": "subnet.update.end",
  "payload": {
    "subnet": {
      "id": uuid of subnet,
      "name": "test-subnet1"
    }
  }
}

2) "test-subnet1" -> "test-subnet2"
{
  "event_type": "subnet.update.start" (different event type),
  "payload": {
    "id": uuid of subnet (note the location of field)
    "subnet": {
      "name": "test-subnet2" (note the absence of id on this level)
    }
  }
}

3) "test-subnet2" -> "test-subnet3"
No message was caught at all

4) "test-subnet3" -> "test-subnet4"
{
  "event_type": "subnet.update.end",
  "payload": {
    "subnet": {
      "id": uuid of subnet,
      "name": "test-subnet4"
    }
  }
}
// The same as in p.1, except for the new name
5) "test-subnet4" -> "test-subnet5"
// The same as in p.2, except for the new name
6) "test-subnet5" -> "test-subnet6"
// The same as in p.3

This cycle repeats in this very order indefinitely.

Environment
===========
1. Mirantis-Mitaka (nova version 13.1.2)
2. libvirt+KVM
3. LVM
4. neutron with OVS
5. Python AMQP listener - kombu 4.0.2

[Sylvain Bauza (sylvain-bauza)]

Reassigning to the Neutron project as the notification is emitted by it.

[Brian Haley (brian-haley)]

Can you test this on master? I believe the message should now contain 'original_subnet' and 'subnet' fields.

[Ilia Abashin (abashinos)]

Hi Brian.
A large part of the issue is that some messages are not posted at all (as described in issue text), some have event_type "subnet.update.start" and the rest have event_type "subnet.update.end". This is a larger problem than placement of fields inside the message.
Is this also fixed on master?
Thanks.

[Kevin Benton (kevinbenton)]

Do you have something else taking notifications off of the queue?

Each API request should result in both a subnet.update.start and a subnet.update.end event. However, the missing events makes it look like there is another subscriber on the queue removing the events.