Override Expires header for proxied content in Apache

apache-2.2

I am serving proxied content with Apache that already contains an Expires header. Using mod_expires' ExpireDefault to override the already present Expires header does not work, the old header is left untouched.

Is there another way to override the Expires header? I tried using mod_headers, but it seems I cannot do date calculation there. I also must override the Expires header, I cannot use Cache-Control with max-age for this.

Regards,
Jochen

Best Answer

As per the HTTP 1.1 specification:

A transparent proxy MUST NOT modify any of the following fields in a response:
  - Expires
but it MAY add any of these fields if not already present. If an Expires header is added, it MUST be given a field-value identical to that of the Date header in that response.

(Quoted from the spec at W3.org.)

You can probably do it using some other hack. An intermediate proxy (such as WebScarab, which I wouldn't use in any production environment) might allow you to intercept and modify any of the headers but a standards-compliant HTTP proxy such as Apache will not permit you to override the Expires header. You can only add it if it's not already there from the origin server, but I'm guessing that the restriction from the spec for adding the Expires header is not going to do what you're looking to do.

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.

Apache Content-Type encoding changing from UTF-8 to iso-88591 from directory to directory

Apache is behaving correctly; PHP is not.

Unfortunately, since all of the string data is being generated out of PHP, you're pretty much dependent on the application you're running having good character set support - look into whether there are any settings you can modify in the application to enable UTF-8 support.

Best Answer

Related Solutions

Linux – Apache gzip configuration

Apache Content-Type encoding changing from UTF-8 to iso-88591 from directory to directory

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