HTTP 409 Conflict

Overview

The HTTP 409 Conflict status code indicates that the request could not be processed because of conflict in the request, such as an edit conflict in the case of multiple updates.

Purpose

The HTTP 409 response is commonly used to indicate a conflict in the state of the resource being requested, typically in situations like concurrent updates, version mismatches, or conflicting operations.

Usage

Client Behavior:

1. Send Request: The client sends an HTTP request that conflicts with the current state of the server.
2. Receive Response: The client receives the HTTP 409 status code, indicating a conflict with the request.

Server Behavior:

1. Evaluate Request: The server determines that processing the request would result in a conflict.
2. Send Response: The server sends a 409 Conflict response, often with a description of the conflict and how to resolve it.

Scenarios

• Concurrent Updates: When two clients try to update the same resource simultaneously.
• Data Mismatches: Conflicts due to data mismatches or violations of the resource’s state.

Sequence Diagram

Illustrating the process for an HTTP 409 response:

sequenceDiagram
    participant Client
    participant Server as Web Server

    Note over Client: Client sends a conflicting request
    Client->>Server: POST /update-resource HTTP/1.1
    Note over Server: Server detects a conflict
    Server->>Client: HTTP/1.1 409 Conflict

Curl Request and Response Example

Sending a conflicting request using Curl:

curl -i -X POST -d "data=conflicting-update" http://example.com/update-resource
# Expected response: HTTP/1.1 409 Conflict

PHP cURL Request and Response Example

PHP script using cURL to handle a 409 Conflict response:

<?php
$ch = curl_init('http://example.com/update-resource');
curl_setopt($ch, CURLOPT_POST, true);
curl_setopt($ch, CURLOPT_POSTFIELDS, 'data=conflicting-update');
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
$response = curl_exec($ch);
if (curl_getinfo($ch, CURLINFO_HTTP_CODE) == 409) {
    echo "Conflict detected.";
}
curl_close($ch);
?>

Python Request and Response Example

Python script to send a conflicting POST request and handle a 409 Conflict response:

import requests
response = requests.post('http://example.com/update-resource', data={'data': 'conflicting-update'})
if response.status_code == 409:
    print("Conflict detected")

Apache Configuration for HTTP 409 Conflict

Configuring Apache to handle conflicts (Specific configurations depend on the nature of the conflict):

<VirtualHost *:80>
    ServerName example.com
    # Configuration directives for handling conflicts
    # ...
</VirtualHost>

NGINX Configuration for HTTP 409 Conflict

Setting up NGINX to manage 409 Conflict responses (Specific configurations depend on the nature of the conflict):

server {
    listen 80;
    server_name example.com;
    location /update-resource {
        # Directives for handling conflicts
        # ...
    }
}

HTTP 408 Request Timeout HTTP 410 Gone