mod_cache questions

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Hello,

As i didn't find any mailing list specific to mod_cache =
development/user-help i thought i could use this one as mod_cache was =
included in mod_proxy with Apache 1.3.

I have to implement cache support in our reverse proxy, running apache =
2.0.36 (Linux), and, as mod_proxy is not caching anymore, i'm checking =
which modules i could use, depending on their features.

Of course i've checked mod_cache, but also 'fcache'. Both don't have any =
complete documentations so i'm kinda stuck.

My questions about mod_cache:
- Can i use the cache (disk and/or ram based cache) in a virtual host =
based server ? Our reverse proxy is serving different internal sites, =
and we want to activate caching for a few sites, but not for all.

- Can i enable (or deny) the cache per URI (directories) and specific =
files (inside a virtual host) ? For example, can i use as default rule =
for a virtual host to not cache anything, except one directory =
containing static pages ?

- How the reverse proxy will act if i tell him to cache dynamic pages ? =
Is there an algorithm or anything used to determine if a page is static =
or dynamic ? (i'm gonna read RFC 2616 right now, i don't know yet if it =
talks about that).

Thank you for your answers, it will greatly help me ...

Arnauld Dravet
smurfie@egocentrique.com

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Re: mod_cache questions

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Arnauld Dravet wrote:

> I have to implement cache support in our reverse proxy, running apache
> 2.0.36 (Linux), and, as mod_proxy is not caching anymore, i'm checking
> which modules i could use, depending on their features.

The caching was stripped from mod_proxy and moved into mod_cache.

> Of course i've checked mod_cache, but also 'fcache'. Both don't have
> any complete documentations so i'm kinda stuck.

Hmmm... must check what docs exist...

> My questions about mod_cache:
> - Can i use the cache (disk and/or ram based cache) in a virtual host
> based server ? Our reverse proxy is serving different internal sites,
> and we want to activate caching for a few sites, but not for all.

(AFAIK) yes.

The main reason the cache was ripped out of proxy was that we wanted
cache to work anywhere in Apache. For example with mod_cgi, or
mod_webapp (for tomcat).

> - Can i enable (or deny) the cache per URI (directories) and specific
> files (inside a virtual host) ? For example, can i use as default rule
> for a virtual host to not cache anything, except one directory
> containing static pages ?

Again, yes. Caching is enabled or disabled for content beneath a
specific URL, configurable by you.

> - How the reverse proxy will act if i tell him to cache dynamic pages
> ? Is there an algorithm or anything used to determine if a page is
> static or dynamic ? (i'm gonna read RFC 2616 right now, i don't know
> yet if it talks about that).

Again yes. RFC2616 explains how HTTP proxies and caches are supposed to
work - to HTTP there is no such thing as "static" or "dynamic", there is
only "content". Look for headers like Cache-Control, Etag, and the stuff
on conditional requests to see how this all works.

Regards,
Graham
--
-----------------------------------------
minfrin@sharp.fm "There's a moon
over Bourbon Street
tonight..."
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Re: mod_cache questions

Hi Graham and thanks for your help :)

I've began to check sources of mod_cache so at least i can see what
directives can be used for each submodule (disk & mem).
Will such an httpd.conf work (can't try it yet i'm not @work) ? A few
things i'm wondering are quoted after the listing.

----------------------------------
##general apache config
LoadModule cache_module modules/mod_cache.so
LoadModule disk_cache_module modules/mod_disk_cache.so
LoadModule mem_cache_module modules/mod_mem_cache.so

##beginning of virtual hosts config
NameVirtualHost 192.168.100.19:80


ServerName web1.test.com
ProxyRequests on
ProxyPass / http://web1.test.com/
ProxyPassReverse / http://web1.test.com/

CacheOn On
CacheRoot /cache/web1 #directory in which we want to disk cache
this virtualhost
CacheSize 1000000 #approx 1GB of disk cache for this
virtualhost
CacheExpiryCheck On #we verify the expiration date of cached
objects
CacheMinFileSize 256000 #we disk cache objects of size >= approx 256KB
CacheMaxFileSize 10000000 #we disk cache objects of size <= approx 10MB
CacheGcUnused 2 #we erase unused cached objects every 2
hours

MCacheSize 64000 #approx 64MB allocated for memory cache
MCacheMinObjectSize 1 #we RAM cache objects of size >= 1 byte
MCacheMaxObjectSize 256000 #we RAM cache objects of size <= 256KBytes

TransferLog /dev/null
ErrorLog /logs/1-error.log



ServerName web2.test.com
ProxyRequests on
ProxyPass / http://web2.test.com/
ProxyPassReverse / http://web2.test.com/


CacheEnable mem / #we ram cache the root dir of web2
CacheEnable disk /pictures #we disk cache
http://web2.test.com/bigfiles/*
CacheEnable mem /bigfiles/thumbnails #we ram cache
http://web2.test.com/bigfiles/thumbnails/*

CacheRoot /cache/web2 #directory in which we want to disk cache
this virtualhost
CacheSize 500000 #approx 500MB of cache for this
virtualhost
CacheExpiryCheck Off #we don't verify the expiration date of
cached objects
CacheMinFileSize 128000 #we disk cache objects of size >= approx
128KB
CacheMaxFileSize 10000000 #we disk cache objects of size <= approx 10MB
CacheGcUnused 5 #we erase unused cached objects every 5
hours

MCacheSize 128000 #approx 128MB allocated for memory cache
MCacheMinObjectSize 1 #we RAM cache objects of size >= 1 byte
MCacheMaxObjectSize 128000 #we RAM cache objects of size <= 128KB

TransferLog /dev/null
ErrorLog /logs/2-error.log


-------------------
QUESTIONS ABOUT THIS EXAMPLE:
- Is it better to use CacheOn On in the global section, and tell in each
VirtualHost i don't want to activate caching CaheOn Off, or should i do like
i did, explicitely use CacheOn On in the VirtualHosts i want to cache ?
- Can i still use CacheEnable if i also use
CacheOn On/Off, in the same VirtualHost ?
- Should i better use CacheOn On ... or
CacheOn On ... to enable cache per directory/location, instead
of using several CacheEnable inside a VirtualHost declaration?
- What happen if CacheMinFileSize < MCacheMaxObjectSize in my example ? Will
mod_cache automatically take the cached object in RAM, which should be
accessed faster than on disk ?
- Finally, is there a way to enable or disable cache per file extension ? ie
deny cache on all files like .php .cgi .asp or requests using an URL with
parameters (using the '?' character) ?





Thank you again ....
Arnauld

--
Arnauld Dravet
smurfie@egocentrique.com