User Defined Resource Error HTTP Status Code

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Table of Contents

1. Note to Readers

Per [RFC7231] Section 8.2.2 this document avoids allocating a specific number for the proposed new HTTP status code until there is clear consensus that it will be registered. The code 5NN is used throughout this document to denote this new status code.¶

2. Introduction

Some HTTP servers offer mechanisms for users to define their own programmatically generated resources. This specification terms such a resource as a 'User Defined Resource'. In such cases it is useful to distinguish between errors arising due to defects in the User Defined Resource and errors arising due to defects in the server itself.¶

This document proposes a new 5NN HTTP status code. This status code indicates that an error occurred when the server attempted to produce a representation of the User Defined Resource, and the error occurred when attempting to evaluate the program that generates the resource, rather than an error condition in the server itself.¶

3. 5NN User Defined Resource Error

The 5NN (User Defined Resource Error) status code indicates that the server encountered an unexpected condition when evaluating a User Defined Resource that prevented the server from fulfilling the request.¶

A 5NN response is not cacheable.¶

The response message MAY contain information that identifies the User Defined Resource that originated the error. The response message SHOULD contain additional information that can help the author of User Defined Resource diagnose the root cause of the error.¶

The response SHOULD include an identifier that uniquely identifies the error condition instance. This identifier should also appear with any log messages or other diagnostic information that the server produces.¶

The response MAY include a URI [RFC3986] that points to a resource that the User Defined Resource author can use to review the log and other diagnostic information associated with the error condition. Access to this URI MUST be restricted to ensure only the User Defined Resource author can access it.¶

It is RECOMMENDED that the server provide the User Defined Resource author with secured access to the logs pertaining to the error instance, and a capability to filter/search these logs keyed by the error identifier.¶

The log information SHOULD provide detailed information about the nature and origin of the error, to enable the User Defined Resource author to diagnose the root cause of the error, whereas the error response SHOULD contain the minimal information required to identify the corresponding log messages.¶

4. IANA Considerations

The HTTP Status Codes Registry should be updated with the following entry:¶

• Code: 5NN¶
• Description: User Defined Resource Error¶
• Specification: [ this document ]¶

5. Security Considerations

When the server includes information that identifies the User Defined Resource that caused the error, or additional information that helps the author diagnose the root cause, care must be taken not to disclose information that may be useful to an attacker.¶

Care needs to be taken to ensure that the log messages do not reveal sensitive information about the users of the User Defined Resource, see [RFC7230] section 9.8 for relevant guidance on this topic.¶

6. Example

This section is non-normative.¶

Below is an example response that leverages the Problem Details for HTTP APIs syntax [RFC7807] to communicate information about the error condition:¶

HTTP/1.1 5NN User Defined Resource Error
Content-Type: application/problem+json
Content-Language: en

{
 "type":     "https://example.com/errs/user-defined-resource-error",
 "title":    "User Defined Resource Error",
 "detail":   "An unexpected error condition occurred when
              evaluating a user defined resource",
 "trace_id": "a75382c4-d61d-4c16-8dde-a01afc7b51a2",
 "instance": "/logs/?trace_id=a75382c4-d61d-4c16-8dde-a01afc7b51a2"
}

• The detail message is careful to reveal minimal information about the User Defined Resource that experienced the error condition.¶
• The trace_id field provides a unique identifier for the error condition that can be used to correlate corresponding log entries and other diagnostic information relevant to this error condition.¶
• The instance URI points to a (secured) resource that can be interrogated to view all the log messages associated with this specific error instance.¶

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