Hi,
I'm trying to figure out what would be the best way to to handle resource
updates. For example, updating an instance named [DTACLOUD-366, DTACLOUD-345].
For now, in Deltacloud we don't support the 'update' operation, however,
some clouds like FGCP (and partially OpenStack/RHEV-M/EC2) do support this
feature.
There are three possible scenarios:
1. Using 'PUT' (PUT /api/instances/inst1):
The request body will contain full representation of the resource (so
basically we will replace the old resource with a new one).
2. Using 'PATCH' (PATCH /api/instances/inst1?name=new_name):
In this case, you can choose what attributes you want to update as query
parameters. It also seems to be a more REST-friendly approach when you're
updating just a single attribute.
3. Using 'POST' (POST /api/instances/inst1/edit?name=new_name):
Basically the same thing as 2), but instead of the PATCH HTTP method, we
can use the
'POST' method on the 'edit' action. The dark side of this approach is that
we are poisioning the URL namespace with '/edit' (that is, the instance ID
can't be set to 'edit').
I known that in the CIMI, updating is done by combination of 1). and 2)
(PUT + '/edit'), which could be our option 4). However, I don't like this
approach, because PUT is meant to replace the whole resource and does not
fit well when you're updating just a single attribute.
The second part of implementing the 'update' operation is to add support
for it into drivers. I think the simpliest way is:
def update_instance(credentials, instance_id, opts={})
# safely do; driver.update_attrs(...) ;end
end
The last part is to mark what attributes are allowed for the update. I
think this will vary from one provider to another. We can both advertise
this usingthe OPTIONS method or just simply return a validation error to
the client when he tries to update a read-only attribute. (Or we can use
the database to store them....)
My personal preference is 2) :-), but I just want to start a discussion
about this before somebody starts writing the code (I know that there are
milions of blogs/articles about updating resources, the problem is what to
choose and what will fit to us ;-)
Cheers,
-- Michal
--
Michal Fojtik <[email protected]>
Deltacloud API, CloudForms
