Initializing help system before first use

# Responses

The Xpress Insight API provides responses using the HTTP protocol.

## Status Codes

The API uses standard HTTP status codes from RFC-7231 and RFC-4918 to indicate success or failure of a request; success is indicated by a status code in the `2xx` range and failure is indicated by a status code in the `4xx` or `5xx` range.

## Timestamps

Timestamps are in ISO-8601 format in accordance with RFC-3339 and are in Coordinated Universal Time (UTC), for example "2021-01-01T10:32:41.266Z".

## Pagination

The API uses pagination for collection-type responses in order to provide flexibility for clients and prevent unnecessary work for the server. Paginated responses are in the form of a page structure containing a subset of the requested resource and information which the client can use to navigate through the entire collection. When paging through collections, clients indicate desired paging properties via request parameters, shown in the following table.

Parameter Name | Description
--- | ---
page | Integer. The number of the page to fetch, starting at 0.
size | Integer. The number of items in the page the client wishes to fetch (minimum 1).

Clients should obey the pagination details in the response, as these may differ from the requested details (for example if the client asks for a page size which is too large).

## Tracing

The API supports the OpenTracing standard used for trace context propagation. Responses contain tracing information using the set of standard `B3` headers (`X-B3-TraceId`, `X-B3-ParentSpanId`, `X-B3-SpanId`, and `X-B3-Sampled`).

## Preferences

The API supports the following optional preferences via the standard `Prefer` HTTP request header:

- `return=minimal` - the client wishes the server to return a minimal response to a successful request
- `return=representation` - the client wishes the server to return the current state of the resource in response to a successful request (default behaviour).

The following example demonstrates how to request a minimal response when submitting a compute job:

    POST /api/compute-jobs HTTP/1.1
    Host: <INSIGHTURL>
    Content-Type: application/vnd.com.fico.xpress.insight.v2+json
    Accept: application/vnd.com.fico.xpress.insight.v2+json
    Prefer: return=minimal
    {...}

A typical server response is shown below:

    HTTP/1.1 201 Created
    Location: https://<INSIGHTURL>/api/compute-jobs/123
    Content-Type: application/vnd.com.fico.xpress.insight.v2+json
    Preference-Applied: return=minimal

Note: RFC-7240 specifies that a requested preference might not be applied by the server, so clients should be tolerant.

## Error Handling

If an error occurs, the server responds with a standard HTTP error code in the `4xx` or `5xx` range, as well as a JSON object that contains error information where this is possible; in some circumstances the server cannot provide this additional information, for example when the client has requested an invalid response content type. Detailed examples of common errors can be found in the API reference documentation.

For example, if a client submitted a Mosel compute job but incorrectly provided solver options in the request, the server would respond with a `422 Unprocessable Entity` response status with an accompanying error in the format below. The client could then use the details provided to perform some further actions, such as displaying information to the end user.

    {
      "error": {
        "code": "FICO-Platform-Http-422",
        "timestamp": "2021-01-01T12:34:56.789Z",
        "desc": "Unprocessable Entity",
        "message": "Validation failed",
        "details": [
          {
            "code": "FICO-Platform-Http-422",
            "timestamp": "2021-01-01T12:34:56.789Z",
            "desc": "Unprocessable Entity",
            "target": null,
            "message": "Solver options are not supported for Mosel jobs"
          }
        ],
        "innerError": null,
        "traceId": "6155b2579dd6935eef68ee3748bf54a2",
        "spanId": "ef68ee3748bf54a2",
        "parentId": null
      }
    }

Parent Topic Accessing the Xpress Insight Server Using the REST API

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