If-Modified-Since vs If-None-Match

apache-2.2cache

This question is based on this article

response header

HTTP/1.1 200 OK
Last-Modified: Tue, 12 Dec 2006 03:03:59 GMT
ETag: "10c24bc-4ab-457e1c1f"
Content-Length: 12195

request header

GET /i/yahoo.gif HTTP/1.1
Host: us.yimg.com
If-Modified-Since: Tue, 12 Dec 2006 03:03:59 GMT
If-None-Match: "10c24bc-4ab-457e1c1f"    
HTTP/1.1 304 Not Modified

In this case browser is sending both If-None-Match and If-Modified-Since. My question is on the server side do I need to match BOTH etag and If-Modified-Since before I send 304.

Should I just look at etag and send 304 if etag is a match. In this case I am ignoring If-Modified-Since .

Best Answer

Excerpt from RFC 2616 "Hypertext Transfer Protocol -- HTTP/1.1"

13.3.4 Rules for When to Use Entity Tags and Last-Modified Dates

...

An HTTP/1.1 origin server, upon receiving a conditional request that includes both a Last-Modified date (e.g., in an If-Modified-Since or If-Unmodified-Since header field) and one or more entity tags (e.g., in an If-Match, If-None-Match, or If-Range header field) as cache validators, MUST NOT return a response status of 304 (Not Modified) unless doing so is consistent with all of the conditional header fields in the request.

Related Solutions

Linux – Apache gzip configuration

Here's an ideal .htaccess that both compresses and sets sutiable expire headers.

# Insert filter
SetOutputFilter DEFLATE

# Netscape 4.x has some problems...
BrowserMatch ^Mozilla/4 gzip-only-text/html

# Netscape 4.06-4.08 have some more problems
BrowserMatch ^Mozilla/4\.0[678] no-gzip

# MSIE masquerades as Netscape, but it is fine
# BrowserMatch \bMSIE !no-gzip !gzip-only-text/html

# Make sure proxies don't deliver the wrong content
Header append Vary User-Agent env=!dont-vary

<IfModule mod_expires.c>
  ExpiresActive On
  ExpiresDefault "access plus 1 seconds"
  ExpiresByType image/x-icon "access plus 2592000 seconds"
  ExpiresByType image/jpeg "access plus 2592000 seconds"
  ExpiresByType image/png "access plus 2592000 seconds"
  ExpiresByType image/gif "access plus 2592000 seconds"
  ExpiresByType application/x-shockwave-flash "access plus 2592000 seconds"
  ExpiresByType text/css "access plus 604800 seconds"
  ExpiresByType text/javascript "access plus 216000 seconds"
  ExpiresByType application/x-javascript "access plus 216000 seconds"
  ExpiresByType text/html "access plus 600 seconds"
  ExpiresByType application/xhtml+xml "access plus 600 seconds"
</IfModule>

<IfModule mod_headers.c>
  <FilesMatch "\\.(ico|jpe?g|png|gif|swf)$">
    Header set Cache-Control "max-age=2592000, public"
  </FilesMatch>
  <FilesMatch "\\.(css)$">
    Header set Cache-Control "max-age=604800, public"
  </FilesMatch>
  <FilesMatch "\\.(js)$">
    Header set Cache-Control "max-age=216000, private"
  </FilesMatch>
  <FilesMatch "\\.(x?html?|php)$">
    Header set Cache-Control "max-age=600, private, must-revalidate"
  </FilesMatch>
</IfModule>

<IfModule mod_headers.c>
  Header unset ETag
</IfModule>
FileETag None

<IfModule mod_headers.c>
  Header unset Last-Modified
</IfModule>

The following article covers what it does and also talks about compression:

http://www.samaxes.com/2009/01/06/more-on-compressing-and-caching-your-site-with-htaccess/

Hope that helps.

Make IIS 7.5 cache static content files over diferent pages

When I first load "~/" of test.dev, all files will load with a response code of 200; when I press F5 in Firefox, all files, except the "~/default.aspx", will load with 304 response code; but pressing Ctrl+F5 loads them again with a 200 code; if I browse another url like "~/pages/" in test.dev, all of those static files will reload with a 200 code... Is this normal or I'm doing something wrong?

In firefox (and most other browsers) shift+F5 reloads the site ignoring the cache.

Best Answer

Related Solutions

Linux – Apache gzip configuration

Make IIS 7.5 cache static content files over diferent pages

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