HTTP 506 Variant Also Negotiates (Experimental)

Overview

The HTTP 506 Variant Also Negotiates status code is an experimental response indicating that the server has an internal configuration error and is unable to perform transparent content negotiation for the request.

Purpose

The HTTP 506 response is used to inform the client that the server encountered an error while attempting to perform content negotiation.

Usage

Client Behavior:

1. Send Request: The client sends an HTTP request with the expectation of content negotiation.
2. Receive Response: The client receives an HTTP 506 status code if the server encounters an error during content negotiation.

Server Behavior:

1. Content Negotiation Error: The server encounters an internal configuration error while attempting content negotiation.
2. Send Response: The server sends a 506 Variant Also Negotiates response to the client.

Scenarios

• Content Negotiation Failure: The server encounters issues while negotiating content variants.

Sequence Diagram

Illustrating the process for an HTTP 506 response:

sequenceDiagram
    participant Client
    participant Server

    Note over Client: Step 1: Client sends a request expecting content negotiation
    Client->>Server: GET /resource HTTP/1.1 (Step 1)

    Note over Server: Step 2: Server encounters internal error during content negotiation
    Server-->>Client: HTTP/1.1 506 Variant Also Negotiates (Step 2)

Curl Request and Response Example

Sending a request using Curl with an expectation of content negotiation:

curl -i -H "Accept: application/json" http://example.com/resource
# Expected response: HTTP/1.1 506 Variant Also Negotiates

PHP cURL Request and Response Example

PHP script using cURL to handle a 506 Variant Also Negotiates response:

<?php
$ch = curl_init('http://example.com/resource');
curl_setopt($ch, CURLOPT_HTTPHEADER, ['Accept: application/json']);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
$response = curl_exec($ch);
if (curl_getinfo($ch, CURLINFO_HTTP_CODE) == 506) {
    echo "Variant Also Negotiates";
}
curl_close($ch);
?>

Python Request and Response Example

Python script sending a request with an expectation of content negotiation and handling a 506 Variant Also Negotiates response:

import requests
response = requests.get('http://example.com/resource', headers={'Accept': 'application/json'})
if response.status_code == 506:
    print("Variant Also Negotiates")

Apache Configuration for HTTP 506 Variant Also Negotiates

Configuring Apache to handle 506 errors:

# Apache Configuration Example
ErrorDocument 506 "Variant Also Negotiates"

NGINX Configuration for HTTP 506 Variant Also Negotiates

NGINX configuration for handling 506 errors:

# NGINX Configuration Example
error_page 506 /506.html;
location = /506.html {
    internal;
    return 506 "Variant Also Negotiates";
}

HTTP 505 HTTP Version Not Supported HTTP 507 Insufficient Storage (WebDAV)