Questions[mod-cache](server)

I have a PHP site that has many dynamically generated pages. I'm trying to turn to mod_cache to help boost performance, because in most cases, content does not change in a given day.

I have configured mod_cache as best I could, following examples around the web, including the mod_cache page on apache.org. When I set LogLevel debug, I see a bit of information about the caching that is [not] happening. There are plenty of pairs of lines like this:

[Fri Jun 01 17:28:18 2012] [debug] mod_cache.c(141): Adding CACHE_SAVE filter for /foo/bar
[Fri Jun 01 17:28:18 2012] [debug] mod_cache.c(148): Adding CACHE_REMOVE_URL filter for /foo/bar

Which is fine, because I've set CacheEnable disk /foo, to indicate that I want everything under /foo cached. I'm new to mod_cache, but my understanding about these lines is that it just means that mod_cache has acknowledged that the URL is supposed to be cached, but there are supposed to be more lines indicating that it is saving the data to cache, and then later retrieving them on subsequent hits to the same URL.

I can hit the same URL till I'm blue in the face, whether with F5 refreshing, or not, or with different browsers, or different computers. It's always that pair of lines that shows in the logs, and nothing else.

When I set CacheEnable disk /, then I see more activity. But I don't want to cache the entire site, and there are many, many different subpaths to the site, so I don't want to have to modify code to set no-cache headers in all the necessary places.

I'll mention that mod_rewrite is in use here, rewriting /foo/bar to something like index.php?baz=/foo/bar, but my understanding is that mod_cache uses the pre-rewrite URL, not the post-rewrite URL.

As far as I can tell, I have the response headers not getting in the way of caching. Here's an example from one hit:

Cache-Control:must-revalidate, max-age=3600
Connection:Keep-Alive
Content-Encoding:gzip
Content-Length:16790
Content-Type:text/html
Date:Fri, 01 Jun 2012 21:43:09 GMT
Expires:Fri,  1 Jun 2012 18:43:09 -0400
Keep-Alive:timeout=15, max=100
Pragma:
Server:Apache
Vary:Accept-Encoding

mod_cache config is as follows:

CacheRoot   /var/cache/apache2/
CacheDirLevels 3
CacheDirLength 2
CacheEnable disk /foo

What is getting in the way of mod_cache doing its job of caching?

Varnish has the possibility to strip certain cookies from the request before deciding if a request is non-cachable because it contains cookies. Is there such a thing for Apache's mod_cache?

Consider this situation: Apache 2.2 is a reverse proxy with lots of configuration (multiple VirtualHosts, 4 backend servers, authentication based on Host and path) that I really like - because it works.

Now to speed up delivery of a Django site, I would like to cache all requests to a certain VirtualHost - except those that carry the Django session cookie (e.g. logged in staff requests). Now the request obviously Varys with cookies, e.g. a logged in user with cookie is always given a freshly rendered page while someone without cookies is given a cached response.

So Vary: cookie would be the correct cache control header to do exactly that: Always freshly render when cookies present. BUT then there is Google Analytics (GA) (and other cookie-based tracking mechanisms like eTracker) that always sets a cookie.

Can Apache ignore that GA-cookie and Vary on the Django session cookie??

I have a very heavy site in my server. The load of the server is always about 30-50 and sometimes it become even 150 and server work really hard. I'm looking for a caching solution that can increase performance of server and decrease the server load.

But I do not know which caching solution I should use? By the way I'm using Drupal CMS and I have WHM/CPanel

Here are options which I found: 1- Memcached 2- Varnish 3- Apache mod_cache

Can someone please give me some comparison or guidance about these platforms? Does mod_cache of Apache work as good as say Varnish? Because installing and configuring Varnish is not a bit complicated in cPanel / WHM. Although I read very good reviews about Varnish.

I'm looking for the best cache solution which can configured straightforward and not complicated. I would appreciate any help or comment.

We're running Plone 3.3.6 behind Apache 2.2.19 with mod_cache. We've recently noticed that Apache is caching the 206 response to a range request and then serving that partial response when a request for the full resource is made.

What seems to happen:

• some client makes a range request for a resource that is not yet in the cache or is in the cache but has expired
• Apache serves the 206 response correctly
• another client makes a standard request the same resource
• Apache serves the same 206 response to this second client: it should serve the entire response with a 200

This is causing problems with our css on some sites very occasionally

I can replicate this consistently: I wrote a little python script to make a range request.

I don't think we're not doing anything out of the ordinary with our Apache configuration. We're using reverse proxy configuration to serve pages from Plone. The Apache configuration relevant to mod_cache is as follows:

CacheEnable disk /
CacheDisable /static
CacheDisable /sitemap.xml.gz
CacheDisable /robots.txt
CacheIgnoreHeaders Set-Cookie

UseCanonicalName On

RequestHeader edit Accept-Encoding ^.*gzip.*$ gzip early
RequestHeader edit Accept-Encoding ^(?!gzip).*$ "" early

The Apache caching guide doesn't include 206 responses in the list of status codes the response "must have" for it to be cached. Is this a bug in Apache or are we doing something wrong in the configuration?

I have an application that has the following rewrite rule:

    RewriteCond /tmp/maintenance.html -f
    RewriteCond %{HTTP_HOST} !^backdoor.myapp.com$
    RewriteRule ^(.*)$ /tmp/maintenance.html [L] 

This is our 'maintenance mode'. so I enable maintenance by linking /tmp/maintenance.html with a real file (and keep backdoor access using backdoor.myapp.com).

Problem is, this page seems to be getting cached by browsers, so when maintenance is turned off, the user has to do a hard refresh in order to get back to the main app.

I'm wondering how I can set the headers for this particular file only in Apache2. I believe there's a no-cache header? I'm assuming I want to set that header for this file, and all should be good.

can someone direct me how to do that, or explain the mechanism by which this static file should never be cached in the user's browser?