[occi-wg] Pagination

[Ralf Nyren]

Hi,

Pagination [1] is currently not defined in the HTTP Rendering. The hope is  
to remedy this in a future version combined with the work to separate the  
OCCI Rendering concept into "transport protocol" and "data format".

Since pagination is a protocol feature rather than a data format issue it  
was concluded during today's confcall that future pagination support in  
OCCI should only affect the transport protocol (if possible). I.e. a data  
format, such as JSON, should not contain any pagination information.

How to implement this over HTTP then? And we do not want any custom HTTP  
headers...

Proposal
-------------

A client must (if desired) request pagination by use of _query_parameters_  
in the HTTP URL.

To solve the issue where a server need to enforce pagination when not  
requested by the client Florian made an interesting proposal.

Let us say an OCCI system has 1000000 Compute instances. An OCCI client  
asking for the full collection (no pagination in the request) must be  
forced to use pagination because the server cannot send back all instances  
of the collection.

The server would then return HTTP status code 301 (redirect) with a URL  
containing the proper pagination parameters the server would have wished  
the client had used in the first place.

Example
------------

< GET /compute/ HTTP/1.0

> HTTP/1.0 301 Moved Permanently
> Location:  
> /compute/?id=urn:uuid:f3ec2e3a-0cc1-11e2-91ed-abf19593d6e2&start=0&end=100

< GET  
/compute/?id=urn:uuid:f3ec2e3a-0cc1-11e2-91ed-abf19593d6e2&start=0&end=100

> HTTP/1.0 200
...

By looking at the query parameters the client would see what pagination  
the server has enforced.

regards, Ralf

[1] http://en.wikipedia.org/wiki/Pagination