Open Stack

Hi Quantum folks,

During the review https://review.openstack.org/#/c/18018/,
A question on the API layer has been raised: What is the meaning of 'None'?

In the review a problem that a meaning of passing 'None' in Quantum API
(action=clear) for an attribute is ambiguous has been raised.
A word "clear" is used in two meanings: (a) to set an empty value,
and (b) to reset to default.

These are similar in many cases, but they have different meanings.
For example, let's assume attribute X is a list and its default value is [1,2].
"Setting an empty value" means that [] is set to X, and "reseting to default"
means that [1,2] is set to X.


I believe these two should be distinguished on the API layer.
The API layer shoule provide:
- a way to set an empty value (e.g., "", [], {}), and
- a way to reset to its default value


IMO, the former is innevitable since the API should not limit a value which
is valid for a specific attribute, and the latter is very useful if supported.

My proposal is
- The API layer provides a way to specify an emtpy value (e.g., "", [], {})
- Make 'None (null in json)' an reserved value and if None is passed a
  corresponding attribute is reset to its default value.


My only concern is gateway_ip attribute of subnet resource.
gateway_ip = None means the subnet has no gateway.
It is different from my proposal above and
we need to keep backward compatibility of the API.
(Of cource I know there were many discussion about gateway_ip = None)

What dou you think?


[Background]

Recently quantumclient introduced "action=clear" which passes 'None'
(null in JSON) to the Quantum server for a specified attribute.
It is originally intended to set an empty value explicitly,
e.g. reset dns_nameservers of subnet to [].

Thanks,
Akihiro