1.5. Faults

When an error occurs, the Block Storage Service returns a fault object containing an HTTP error response code that denotes the type of error. In the body of the response, the system will return additional information about the fault.

The following table lists possible fault types with their associated error codes and descriptions.

Fault Type	Associated Error Code	Description
`badRequest`	400	There was one or more errors in the user request.
`unauthorized`	401	The supplied token is not authorized to access the resources, either it's expired or invalid.
`forbidden`	403	Access to the requested resource was denied.
`itemNotFound`	404	The back-end services did not find anything matching the Request-URI.
`badMethod`	405	The request method is not allowed for this resource.
`overLimit`	413	Either the number of entities in the request is larger than allowed limits, or the user has exceeded allowable request rate limits. See the `details` element for more specifics. Contact support if you think you need higher request rate limits.
`badMediaType`	415	The requested content type is not supported by this service.
`unprocessableEntity`	422	The requested resource could not be processed on at the moment.
`instanceFault`	500	This is a generic server error and the message contains the reason for the error. This error could wrap several error messages and is a catch all.
`notImplemented`	501	The requested method or resource is not implemented.
`serviceUnavailable`	503	The Block Storage Service is not available.

The following two instanceFault examples show errors when the server has erred or cannot perform the requested operation:

Example 1.4. Example instanceFault Response: XML

HTTP/1.1 500 Internal Server Error
Content-Type: application/xml
Content-Length: 121
Date: Mon, 28 Nov 2011 18:19:37 GMT

          <?xml version="1.0" encoding="UTF-8"?>
<instanceFault code="500"
    xmlns="http://docs.rackspace.com/cbs/api/v1.0">
    <message> The server has either erred or is incapable of
        performing the requested operation. </message>
</instanceFault>

Example 1.5. Example Fault Response: JSON

HTTP/1.1 500 Internal Server Error
Content-Length: 120
Content-Type: application/json; charset=UTF-8
Date: Tue, 29 Nov 2011 00:33:48 GMT

          {
    "instanceFault": {
        "code": 500,
        "message": "The server has either erred or is incapable of performing the requested operation."
    }
}

The error code (code) is returned in the body of the response for convenience. The message element returns a human-readable message that is appropriate for display to the end user. The details element is optional and may contain information that is useful for tracking down an error, such as a stack trace. The details element may or may not be appropriate for display to an end user, depending on the role and experience of the end user.

The fault's root element (for example, instanceFault) may change depending on the type of error.

The following two badRequest examples show errors when the volume size is invalid:

Example 1.6. Example badRequest Fault on Volume Size Errors: XML

HTTP/1.1 400 None
Content-Type: application/xml
Content-Length: 121
Date: Mon, 28 Nov 2011 18:19:37 GMT

<?xml version="1.0" encoding="UTF-8"?>
<badRequest code="400"
    xmlns="http://docs.openstack.org/api/openstack-volume/1.0/content">
    <message> Volume 'size' needs to be a positive integer value, -1.0
        cannot be accepted. </message>
</badRequest>

Example 1.7. Example badRequest Fault on Volume Size Errors: JSON

HTTP/1.1 400 None
Content-Length: 120
Content-Type: application/json; charset=UTF-8
Date: Tue, 29 Nov 2011 00:33:48 GMT

{
    "badRequest": {
        "code": 400,
        "message": "Volume 'size' needs to be a positive integer value, -1.0 cannot be accepted."
    }
}

The next two examples show itemNotFound errors:

Example 1.8. Example itemNotFound Fault: XML

HTTP/1.1 404 Not Found
Content-Length: 147
Content-Type: application/xml; charset=UTF-8
Date: Mon, 28 Nov 2011 19:50:15 GMT

<?xml version="1.0" encoding="UTF-8"?>
<itemNotFound code="404"
    xmlns="http://docs.openstack.org/api/openstack-volume/1.0/content">
    <message> The resource could not be found. </message>
</itemNotFound>

Example 1.9. Example itemNotFound Fault: JSON

HTTP/1.1 404 Not Found
Content-Length: 78
Content-Type: application/json; charset=UTF-8
Date: Tue, 29 Nov 2011 00:35:24 GMT

{
    "itemNotFound": {
        "code": 404,
        "message": "The resource could not be found."
    }
}

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