Name Based Virtual Hosting irule efficiency

I have put in place the irule along with the custom health monitor for each application. We are testing out two applications and the two that applications that are using the monitor are working and directing traffic with and without the irule.

Here is the setup:

pool test1.pool nodes 10.1.1.1 10.1.1.2 monitor GET /f5-monitor/f5-monitor.jsp HTTP/1.1\r\nHost: test1.com\r\nConnection: Close\r\n\r\n

pool test2.pool nodes 10.1.1.1 10.1.1.2 monitor GET /f5-monitor/f5-monitor.jsp HTTP/1.1\r\nHost: test2.com\r\nConnection: Close\r\n\r\n

I am able to get to test1.com and test2 with and without the use of the irule or data groups. How's this happening since the nodes are using the same pair of apache servers that are serving up the host header information and properly being routed to each application?

Thanks

I have put in place the irule along with the custom health monitor for each application. We are testing out two applications and the two that applications that are using the monitor are working and directing traffic with and without the irule.

Here is the setup:

pool test1.pool nodes 10.1.1.1 10.1.1.2 monitor GET /f5-monitor/f5-monitor.jsp HTTP/1.1\r\nHost: test1.com\r\nConnection: Close\r\n\r\n

pool test2.pool nodes 10.1.1.1 10.1.1.2 monitor GET /f5-monitor/f5-monitor.jsp HTTP/1.1\r\nHost: test2.com\r\nConnection: Close\r\n\r\n

I am able to get to test1.com and test2 with and without the use of the irule or data groups. How's this happening since the nodes are using the same pair of apache servers that are serving up the host header information and properly being routed to each application?

Thanks

all great stuff guys, thanks for the input and help again!

irule is editor has helped alot I download it a a coulple of months ago..would awesome if there it came bundled with the devices so that all you have to do is just click a download link and than install it locally to your machine. Instead of going to the dev central directly.

if I was going to use a list that would just match against host headers would I just use a class ? is that something I do in the irule itself or done in tmos ? confused when it comes to some of the examples

Thanks

@michael j has it right - data groups are probably best for dealing with matching against a large list of items or matching against a list that changes often. A few of the biggest advantages to using data groups over "if/then" or "switch" logic are readability and you should rarely have to touch the iRule itself. Adding a new hostname/pool-name pair just requires adding an entry to a data-group.

If you want to base the pool selection on the requested HTTP host header, you can try something like:

A data group with string entries of name: HTTP hostname and value: pool-name

ltm data-group internal test-dg {
    records {
        abc.com {
            data abc_pool
        }
        def.com {
            data def_pool
        }
    }
    type string
}

The associated iRule:

when HTTP_REQUEST {
 test-dg is a string data-group where the entries are name:value pairs
 name is the requested HTTP host header, value is the associated pool-name

     check the requested HTTP host header against entries in data-group test-dg
    if { [class match [string tolower [HTTP::host]] equals test-dg ] } {
         if the HTTP host header is in test-dg
         send the request to the pool associated with the test-dg entry
        pool [class match -value [string tolower [HTTP::host]] equals test-dg ]
    } else {
         drop the request if the host header is not in test-dg
        drop
}
}

@michael j has it right - data groups are probably best for dealing with matching against a large list of items or matching against a list that changes often. A few of the biggest advantages to using data groups over "if/then" or "switch" logic are readability and you should rarely have to touch the iRule itself. Adding a new hostname/pool-name pair just requires adding an entry to a data-group.

If you want to base the pool selection on the requested HTTP host header, you can try something like:

A data group with string entries of name: HTTP hostname and value: pool-name

ltm data-group internal test-dg {
    records {
        abc.com {
            data abc_pool
        }
        def.com {
            data def_pool
        }
    }
    type string
}

The associated iRule:

when HTTP_REQUEST {
 test-dg is a string data-group where the entries are name:value pairs
 name is the requested HTTP host header, value is the associated pool-name

     check the requested HTTP host header against entries in data-group test-dg
    if { [class match [string tolower [HTTP::host]] equals test-dg ] } {
         if the HTTP host header is in test-dg
         send the request to the pool associated with the test-dg entry
        pool [class match -value [string tolower [HTTP::host]] equals test-dg ]
    } else {
         drop the request if the host header is not in test-dg
        drop
}
}

Thanks for the great response. For me at least if the backend web servers are going to be using the same set apache ips I would have to create new pools containing the same set of ips, a seperate monitor, than add the pool to the irule that I pasted.

From my experience (as we do something similar in my organization), we've used data groups to handle all this (and parse the values to get information we need).

Regarding how to interact with data groups, this wiki page gives links to the class, findclass and matchclass functions, which should help guide you in the right direction.

For us, we sometimes use a format like

name1:value1|name2:value2|...

• DG Record Name:

  example.com

• DG Record Value:

  pool:my_pool|host:www.mynewhost.com

So in our iRule, we would check for

example.com

set host [string tolower [HTTP::uri]]
if { [class match $host equals DATA_GROUP_NAME] } {
    set param [class match -value $host equals DATA_GROUP_NAME]
     Add some checking for data integrity if necesary

    set params [split $param "|"]
    set pool [getfield [lsearch -inline -glob $params "pool:*"] ":" 2]
    set host [getfield [lsearch -inline -glob $params "host:*"] ":" 2]

     Set the pool
    pool $pool
     Change the host
    HTTP::host $host
}

It's a simple example, and depending on the amount of traffic, may not be the most efficient way of doing it, but I've found it's the simplest, as we just add a record to the data group and don't have to touch the iRule.

Hope this helps.