iRule RAM CACHE odd behaviour

Hi Bijan,

What does your HTTP profile look like? How do you view cache hits?

when CACHE_REQUEST {
    log local0. "Request for cached object $uriadd"
}
when CACHE_RESPONSE {
    log local0. "About to send cached response for $uriadd"
}

I've just added the cache response and there are no returned hits in the log.

Worth mentioning perhaps that this site has multiple white labels that run from the same IIS site and thus the same assets folder. so you could hit the same assets folder from 3 seperate [HTTP::HOSTS] but be sent to the same place. not sure what difference that will make?

See if this makes a difference - explicitly enabling/disabling CACHE from HTTP_RESPONSE - apologies in advance - I have taken some liberties with the format of your original iRule (although retained the logic I hope);-

when HTTP_REQUEST {
    set fCache 0
    switch -glob [string tolower [HTTP::host]] {
        "someURL.test.co.uk"  {
            if { !([class match [IP::remote_addr] equals CUST_IP_Addresses])
            and !([class match [IP::remote_addr] equals MIC_IP_Addresses])
            and !([class match [IP::remote_addr] equals private_net]) } {
                drop 
                return
            } else {
                CACHE::disable
                pool "CUST-someURL.test.co.uk_[TCP::local_port]_POOL"
                return
            }
        }
        "someAURL.test.co.uk" {
            pool "CUST-someAURL.test.co.uk_[TCP::local_port]_POOL"
        }
        "*test.co.uk" {
            pool "CUST-www.test.co.uk_[TCP::local_port]_POOL"
        }
        "*test1.co.uk" {
            pool "CUST-test1.co.uk_[TCP::local_port]_POOL"
        } 
        default {
            pool "CUST-test2.co.uk_[TCP::local_port]_POOL"
        }
    }

    switch [getfield [string tolower [URI::basename [HTTP::path]]] "." 2] {
        "js" -
        "pdf" -
        "css" -
        "jpg" -
        "png" {
             enable the cache
            CACHE::enable
            set fCache 1
        }       
        default {
             disable the cache
            CACHE::disable
        }
    }
}
when HTTP_RESPONSE {
    if {$fCache} {
        CACHE::enable
    } else {
        CACHE::disable
    }
}

Thanks for that, I will attempt this on a staging site to see if it works. Worth mentioning though that the original code is in use and working for other sites, although slightly different logic, but the cache enable and disable rules are the same. Just this one customer that it is refusing to utilise the cache properly. Really appreciate your time. will let you know how it goes. thanks

Quick thought... you're using HTTP::uri, not HTTP::path. The URI could have other data (query strings, etc...) at the end, which could be messing with the ends_with setting. We usually do something more like (where 'static_content' is a data group of extensions we want cached):

set VsRAMCacheState [PROFILE::http ramcache]
set content_extension [string range [HTTP::path] [string last . [HTTP::path]] end]
if {  $VsRAMCacheState == 1 } {
    CACHE::disable
    if { [ class match $content_extension equals static_content ] }{
        enable
    } 
}

Bijan,

Could it be that the HTTP profile applied for the VIP for which caching IS working is different?

q Have you checked the profile?

tmsh ltm show profile http

Then look for "Cache Size" to tell if it has been allocated as you requested.

Sorry;

Have you checked the profile?

tmsh 
ltm 
show profile http 

Then look for "Cache Size" to tell if it has been allocated as you requested.

I think I have cracked it. We are out of available RAM in the units so it cannot assign any more RAM CACHE. The errors I expect based on the documentation from F5 are not appearing in the logs but this is my best guess. I'm waiting for our support contracts to be sorted out so that I can get an F5 engineer to confirm my suspicions, and then request more RAM and a software update.

Go and look at all the profiles you have assigned and add up the "Maximum Cache sizes" from the config. That's the figure that you are using actually using per-TMM.

I assume you have seen this http://support.f5.com/kb/en-us/solutions/public/12000/200/sol12225.html?sr=11064657

Check your log for the error message - if you can't find it as you have lost the logs try updating the profile that didn't allocate (just change one thing) and save - you should see the error message then.

Go and look at what you are actually using compared to you Maximum cache size - you'll probably find a few you can reduce the Maximum Cache Size on.

So after lots of different advice it turns out that the reporting on the F5 is at fault. Even though the RAM CACHE reports 0 files in the cache and 0 files in the cache, it has actually cached it. This behaviour was checked by F5 and WestCon support and shown through wireshark that in fact the data is in the cache and being served from the RAM CACHE. This could be a unique feature of 10.2.3 F5 and WestCon are yet to prescribe a fix or resolution to this problem. In the meantime we have scheduled downtime for an upgrade to the latest 11 version. Many thanks to all who helped.