http - Update an entire resource collection in a REST way

Question

I have a REST URI for a list of resources, something like:

http://foo.com/group/users

Each of these users has a sequence number and I want to expose a way to renumber those values for all the users in the collection and make this change available to everyone who accesses the list. Since this is an action on the collection as a whole, I'm not sure how to accomplish this.

I can envision a URL like http://foo.com/group/users?sequence=normalize but neither a PUT nor a POST really makes sense for the whole list, unless I submit the whole collection with the new numbers as the message data.

How can I make an update to an entire collection like this in a RESTful way without having to resend all the updated resources in the collection?

Answer 1

After the raffian's comment on my initial response, I reworked my answer to be more RESTful...

• Use the method PATCH

This method is typically designed to update partially the state of a resource. In the case of a list resource, we could send a list with only the elements to update and the identifiers of elements in the list. The following request would be:

PATCH /group/users
[
    { "id": "userId1", "sequence": "newSequenceNumber1" },
    { "id": "userId2", "sequence": "newSequenceNumber2" },
    (...)
]

• Use the method POST on the list resource

This method is commonly used to add an element in the list managed by the resource. So if you want to leverage it for this action, we need to pass within the request an hint regarding the action to execute. We have the choice to add this either in a dedicated header or within the payload.

With the header approach, you will have something like that:

POST /group/users
X-Action: renumbering
[
    { "id": "userId1", "sequence": "newSequenceNumber1" },
    { "id": "userId2", "sequence": "newSequenceNumber2" },
    (...)
]

With the payload approach, you will have something like that:

POST /group/users
{
    "action": "renumbering",
    "list": {
        [
            { "id": "userId1", "sequence": "newSequenceNumber1" },
            { "id": "userId2", "sequence": "newSequenceNumber2" },
            (...)
        ]
    }
}

Hope it helps you, Thierry