Hi Devs,
We are adding support for returning 'x-openstack-request-id' to the caller as
per the design proposed in cross-project specs:
http://specs.openstack.org/openstack/openstack-specs/specs/return-request-id.html
Problem Description:
Cannot add a new property of list type to the warlock.model object.
How is a model object created:
Let's take an example of glanceclient.api.v2.images.get() call [1]:
Here after getting the response we call model() method. This model() does the
job of creating a warlock.model object(essentially a dict) based on the schema
given as argument (image schema retrieved from glance in this case). Inside
model() the raw() method simply return the image schema as JSON object. The
advantage of this warlock.model object over a simple dict is that it validates
any changes to object based on the rules specified in the reference schema.
The keys of this model object are available as object properties to the caller.
Underlying reason:
The schema for different sub APIs is returned a bit differently. For images,
metadef APIs glance.schema.Schema.raw() is used which returns a schema
containing "additionalProperties": {"type": "string"}. Whereas for members and
tasks APIs glance.schema.Schema.minimal() is used to return schema object which
does not contain "additionalProperties".
So we can add extra properties of any type to the model object returned from
members or tasks API but for images and metadef APIs we can only add properties
which can be of type string. Also for the latter case we depend on the glance
configuration to allow additional properties.
As per our analysis we have come up with two approaches for resolving this
issue:
Approach #1: Inject request_ids property in the warlock model object in glance
client
Here we do the following:
1. Inject the 'request_ids' as additional property into the model
object(returned from model())
2. Return the model object which now contains request_ids property
Limitations:
1. Because the glance schemas for images and metadef only allows additional
properties of type string, so even though natural type of request_ids should be
list we have to make it as a comma separated 'string' of request ids as a
compromise.
2. Lot of extra code is needed to wrap objects returned from the client API so
that the caller can get request ids. For example we need to write wrapper
classes for dict, list, str, tuple, generator.
3. Not a good design as we are adding a property which should actually be a
base property but added as additional property as a compromise.
4. There is a dependency on glance whether to allow custom/additional
properties or not. [2]
Approach #2: Add 'request_ids' property to all schema definitions in glance
Here we add 'request_ids' property as follows to the various APIs (schema):
"request_ids": {
"type": "array",
"items": {
"type": "string"
}
}
Doing this will make changes in glance client very simple as compared to
approach#1.
This also looks a better design as it will be consistent.
We simply need to modify the request_ids property in various API calls for
example glanceclient.v2.images.get().
Please let us know which approach is better or any suggestions for the same.
[1]
https://github.com/openstack/python-glanceclient/blob/master/glanceclient/v2/images.py#L179
[2] https://github.com/openstack/glance/blob/master/glance/api/v2/images.py#L944
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