304 What is a Conditional Rule?

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  • 304 What is a Conditional Rule?

The 304-status code is an HTTP response status code indicating that the requested resource has not been modified since the last access. It is used for storage to optimize network performance and improve load time.
304 Key points about conditional rules:
The 304-status code shows “Unchanged”. It tells the client (web page, etc.) that the resource has not changed since the last request.
Conditional Request:
This status code is part of the HTTP status request process. The client uses conditional queries with headers such as If-Modified-Since or If-None-Match to determine if the object has changed.
No physical features:
If the server responds with a 304 status code, it does not include the body of the resource. The client can use its archived copy instead.
Improving efficiency:
The use of 304 responses allows servers to reduce bandwidth usage and load times because clients do not have to download the same information over and over again if it does not change
HTTP Headers:
Topics commonly associated with the 304 responses include:
ETag: A pointer to a specific element in the object.
Last-Modified: The date and time the resource was last modified.
Cache-Control: Guidelines for caching mechanisms in requests and responses.
If-None-Match: The client is sent to check if the ETag matches the current version of the object.

If-Modified-Since: Submitted by the user to check if the item has changed since the specified date.
Example scenario:
First Request:
The client requests a resource (e.g. HTML page) from the server.
The server responds with the resource, including the ETag and Last-Modified headers.
The next request:
If-None-Match or If-Modified-Since headers are added to ensure that the object has changed when the client requests the same object again.
If the resource has not changed, the server responds with a 304 status code, indicating that the client should use the cached version.

Example HTTP Exchange:

  • Initial Response:
  • http

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  • GET /index.html HTTP/1.1
  • Host: www.example.com
  • HTTP/1.1 200 OK
  • ETag: “686897696a7c876b7e”
  • Last-Modified: Wed, 21 Oct 2015 07:28:00 GMT
  • Content-Type: text/html
  • Content-Length: 1234
  • <html>…content…</html>

Conditional Request:

  • http

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  • GET /index.html HTTP/1.1
  • Host: www.example.com
  • If-None-Match: “686897696a7c876b7e”
  • If-Modified-Since: Wed, 21 Oct 2015 07:28:00 GMT

HTTP/1.1 304 No changes
The 304-status code is an integral part of the HTTP protocol for efficient web performance, allowing clients to make more efficient use of stored data when things have not changed This helps to reduce unnecessary data transfers and to web pages are faster for users.
304 To edit a status code
The 304-status code known as “Not Modified” is an HTTP response status code indicating that the requested object has not changed since the last time it was logged in. This status code is used for caching and helps improve web performance by the need to transfer the same data over and over again. However, if you’re having trouble with a 304 status code, it could be due to a few common problems. Here are the steps to identify and troubleshoot problems associated with the 304 status code:
1. Clear the Browser Cache
Sometimes a 304 status code can cause problems if the browser cache is corrupted or expired.
For Google Chrome:
Click on the three dots in the upper right corner.
Go to More Tools > Clear Browsing Data.
Select “Cached images and files” to delete the data.
For Firefox :
Click on the three vertical dots in the upper right corner.
Go to Options > Privacy and Security.
Click “Clear Data” under Cookies and Site Data.
For safaris:
Go to Safari > Preferences.
Select the “Privacy” tab and click on “Manage Website Data”.
Remove all data.

2. Check the server configuration
Make sure your web server is properly configured to handle If-Modified-Since or ETag headers, which are used to determine if an object has been modified.
Ensure mod_headers and mod_cache modules are enabled.
Check your .htaccess file or server configuration for proper caching instructions.
For example:
<IfModule mod_expires.c> ExpiresActive On ExpiresByType image/jpg “Login Plus 1 Month” ExpiresByType image/jpeg “Login Plus 1 Month” ExpiresByType image/gif “Login Plus 1 Month” ExpiresByType image/png “Login Plus 1 Month” ExpiresByType image/png text /css “add-on is 1 week” ExpiresByType text/html “add-on is 1 day” ExpiresByType application/pdf “add-on is 1 month” ExpiresByType text/x-javascript “add-on is about 1 week” ExpiresByType application/x-shockwave-flash “paths .” and tenth 1″ </IfModule> inclusive

Ensure that the ngx_http_headers_module module is enabled.
Add caching headers to your server configuration.
For example:
accounting skills
location ~* \.(jpg|jpeg|gif|png|css|js|ico|pdf|flv|svg)$ { end of 30d; add_header Cache-Control “public, no change”; } . } . } . } .
3. Check the proxy or CDN settings
If you are using a proxy server or content delivery network (CDN), make sure it is properly configured to handle caching and 304 responses.
CDN Configuration:
Verify the cache settings in your CDN dashboard.
Make sure the CDN respects the root server’s caching headers.
Proxy Server Usage:
Make sure your proxy server forwards and handles If-Modified-Since or ETag headers correctly.
Squid proxy example:
Written by Yamal
refresh_pattern ^ftp: 1440 20% 10080 refresh_pattern ^gopher: 1440 0% 1440 refresh_pattern -i (/cgi-bin/|\?) 0 0% 0 refresh_pattern . 0 20%

4. Validate the HTTP Headers
Verify that the sent and received HTTP headers are correct. Use browser developer tools or online services like cURL to manage titles.
Using cURL:
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curl -I -X GET https://example.com
Look for topics like ETag, Last-Modified, Cache-Control, and Expires.
5. Check the application logic
If your application programmatically sets the caching header, check that the logic is correct.
Example in PHP:
$lastModified = fileTime($file); $etag = md5_file($file); header (‘lastModified: ‘ . gmdate(‘D, d M Y H: i: s’, $lastModified) . ‘ GMT’); title(‘ETag: ‘ . $etag); if (@strtotime($_SERVER[‘HTTP_IF_MODIFIED_SINCE’]) == $lastModified || trim($_SERVER[‘HTTP_IF_NONE_MATCH’]) == $etag) { header(‘HTTP/1.1304 not modified’); of; } . } . } . } .
6. Server logs and debugging
Check your server logs for errors or incorrect archiving settings.
Apache Notes:
tree -f /var/log/apache2/access.log tree -f /var/log/apache2/errors.log
Nginx Notes: 1.1.
tree -f /var/log/nginx/access.log tree -f /var/log/nginx/errors.log
7. testing and verification
Make the necessary adjustments, and test your website with different tools to ensure that the 304 status code is handled properly.
Google Chrome Toolbar:
Open DevTools (F12 or right-click and select “Inspect”).
Go to the “Network” tab and refresh the page.
Check status codes for resources.
Online tools:
Use online tools such as Pingdom, GTmetrix, or WebPageTest to verify caching behavior and status codes.
By following these steps, you can effectively handle 304 issues related to status codes and ensure that your site’s archiving mechanisms are working properly.

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