expires header for images iRule v11.x

I made the expiration duration dynamically assigned from the datagroup value field as your requirements show.

I also adjusted how the extension is obtained to make a more accurate decision. I did so by inspecting the [URI::basename [HTTP::uri]] rather than the entire [HTTP::uri] which could contain a query and parameters. Even though css and image links usually do not contain queries, it does not hurt to be accurate.

NOTE: I did not test the changes I made. If you can test and let us know it would be great.

ltm data-group internal /Common/class_cacheable_file_types {
    records {
     ".css 86400"     
     ".js 86400" 
     ".bmp 604800"     
     ".gif 604800"     
     ".jpeg 604800"     
     ".jpg 604800"     
     ".png 604800"  
     ".ico 604800"  
    }
   type string
}

ltm data-group internal /Common/no_cache_directives {
    records {
    "private"
    "no"
    "max-age"
    }
}

ltm data-group internal /Common/cached_content_types {
    records {
    "java"
    "image"
    "css"
    "plain"
    }
}

rule suppress_304 {
when RULE_INIT {
     0 - No, 1 - Yes.
    set static::obey_response_headers 0

}

when HTTP_REQUEST {

    set inject_maxage 0
    set cache_seconds [class lookup [URI::basename [HTTP::uri]] ends_with /Common/class_cacheable_file_types ]
    if { not ($cache_seconds equals "") } { 
        set inject_maxage 1
    }
}

when HTTP_RESPONSE {

    if {
        not (
            $static::obey_response_headers and 
            (
            [class match [HTTP::header "Cache-Control"] contains /Common/no_cache_directives] ||
            [HTTP::header exists "Expires" ]
                ) 
        )
        and 
        (
            $inject_maxage == 1 || 
            [HTTP::query] eq "" and
            [class match [HTTP::header "Content-type"] contains /Common/cached_content_types] 
        )
    } {
        HTTP::header replace Cache-Control "max-age=$cache_seconds"
    }
}