7.5 Read Error Handling
In response to a read request, the SData provider MUST return one of the following HTTP status codes:
| Code | Description |
|---|---|
| 200 OK | Read was successful. Response contains a valid <entry>. |
| 304 Not Modified | Read was successful. Response is identical to what the consumer has in its cache. Response payload is empty. |
| 400 Bad Request | Generic status for consumer side error. Client MUST modify the request before resubmitting. |
| 401 Unauthorized | Request requires user authentication. See Authentication section for details. |
| 403 Forbidden | Consumer is not authorized to read the requested resource. |
| 404 Not Found | The resource does not exist. See note below. |
| 500 Internal Server Error | Serious provider error. Client SHOULD NOT retry the request. |
| 503 Service Unavailable | Transient provider error. Client MAY retry the request. The provider SHOULD include a Retry-After header in its response to indicate when the consumer MAY retry the request. |
Query and read operations handle the 404 case differently. For a read operation, a 404 status MUST be returned if the resource doesn't exist. For a query, a 200 status MUST be returned with an empty feed when the query doesn't select any resource. See Query Error Handling section.
When the service returns a 4xx or a 5xx status code, it SHOULD include an <sdata:diagnoses> payload with details about the error in its response. See Error Payload section for details.
When the service returns a 200 status code, the entry MAY include one or more <sdata:diagnosis> elements. In this case, the diagnosis elements MUST only be warnings or information.
SData providers MUST return errors as described above.