Expression Persistence

The simplest way to accomplish this is using the pool select attribute.

For example:

 
 pool webpool { 
    select node(findstr(http_uri, "?", 1) + ":80") 
    persist_timeout 60 
    member 10.4.4.3:http 
    member 10.4.4.101:http 
 } 
 

Thanks!

Sorry to be confusing.

 

There are three different ways to solve your problem: a rule, a pool with a persist expression (universal persistence), a pool with a select expression. Because you have the IP address in the URI the select expression is the most efficient. However, I included a persist timeout for the persist expression in the my code example. This timeout is unnecessary because a select expression is not persistence and therefore does not create persistence sessions that need to be timed out. You can turn on one of the persistence modes at the same time as using a select expression but traffic would continue to be directed by the select expression.

 

 

Another important point, the third argument in the findstr function is the offset. Therefore, you need to use a 6 to jump over "bigip=":

 

node(findstr(http_uri, "bigip=", 6) + ":80")

 

 

Read the Reference Guide iRules section for more details.

 

Gumby,

 

 

A while back I contacted you about using expression persistenance. The people I was researching us this for just now want to put this in place. I tried the following and got an error.

 

 

pool WIRELESSDEV-80 {

 

select node(findstr(http_uri, "bigip=", 6) + ":80")

 

member 163.231.95.94:http

 

member 163.231.102.154:http

 

}

 

 

Error331835 -- Rule string to tree failed. - syntax error at 'pool'

 

line 1:pool WIRELESSDEV-80 {

 

 

WIRELESSDEV-80 is the name of the pool, and the 2 memebers are the ip's of the boxes in the pool. I guess I am not sure what the error means, string to tree failed? I looked at the release notes in iRules, but it is not really helping. Can you tell me what is wrong with the rule, or the way I have it defined?

 

 

Thanks for you help,

 

Hank

Hank,

if you are entering the pool from command line (i.e. using bigpipe) you

need to put single quotes around the expression in order to avoid interference with shell globbing and expansion. The command should look like this:

b pool WIRELESSDEV-80 { select 'node(findstr(http_uri, "bigip=", 6) + ":80")' member 163.231.95.94:http ember 163.231.102.154:http }

If you are entering the select expression from the GUI, put just:

node(findstr(http_uri, "bigip=", 6) + ":80"

into the "Node SelectExpression" field on the Pools->Pool->Persistence

page.

The pool statement should work exactly as you have it when entering the configuration by manually editting /config/bigip.conf.

I've tested all of the alternatives on BIG-IP 4.6.4 and all of them worked for me 🙂