HTTP status code for "response too large"

[Andreas Maier <[e-mail]>]

Hi Mark,
I am working for IBM in the DMTF standards org. We are defining a RESTful
protocol for CIM based directly on HTTP ("CIM-RS"), and we want to be as
truthfully RESTful and HTTP compliant as possible.

We want to support an "expand" query parameter that causes references to
resources in the result to be expanded to the resources that they
reference. One of the error situations in this context is that the
expansion can lead to a result that is too large to handle for the server
(e.g. in cases of high mutiplicities on CIM associations). The recovery for
this situation is that the client specifies less expansions in the first
request issues subsequent requests for separate expansion (one per
reference, which can then be paged into multiple responses in case of high
multiplicities).

So it is not the typical server-side recovery, where the client waits for
less load on the server or the server admin needs to add more resources to
the server. The recovery attempt can be immediately decided upon by the
client without any change in server configuration or workload.

We'd like to have a HTTP status code that allows the client to detect this
situation so it can recover from it. In order to make it easy for the
client, I think that should not be a use of status code 500, but its own
status code. I checked all status codes on the IANA HTTP status code
registry and found no one that matched this situation. But I found that the
HTTP WG is working on an RFC for additional HTTP status codes that is
currently in draft :-)

So my questions to you and the WG are:
   - Do you have a recommendation on how to handle this situation?
   - How is your view on the idea to add an HTTP status code for "response
   too large"?

PS: If you're interested in CIM-RS, what you find currently on the DMTF
site or when googling it are informational specs from an incubator that do
not yet have the "expand" query parameter. The real specs from the CIM-RS
WG are about to be released as a Work in Progress in the next weeks.

Andy

Andreas Maier
IBM Senior Technical Staff Member, Systems Management Architecture & Design
IBM Research & Development Laboratory Boeblingen, Germany
[e-mail], [phone]
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