Forum Discussion
Patrick_McGlyn1
Nimbostratus
NimbostratusApplication migration iRule
I am trying to write an iRule to migrate applications from an old web farm pool to a new web farm pool. The web servers are setup to run multiple
application instances on the same IP and Port.
For example,
VIP 2.1.1.1:443 with SSL termination and cookie persistence
Old Web Pool
APP1 – 1.1.1.1:80/APP1/login.html, 1.1.1.2:80/APP1/login.html
APP2 – 1.1.1.1:80/APP2/login.html, 1.1.1.2:80/APP2/login.html
APP3 – 1.1.1.1:80/APP3/login.html, 1.1.1.2:80/APP3/login.html
New Web Pool
APP1 – 1.1.1.10:8080/APP1/login.html, 1.1.1.11:8080/APP1/login.html
APP2 – 1.1.1.10:8080/APP2/login.html, 1.1.1.11:8080/APP2/login.html
APP3 – 1.1.1.10:8080/APP3/login.html, 1.1.1.11:8080/APP3/login.html
I wrote the iRule to select the pool base on the URI as follows:
when HTTP_REQUEST {
set time_out 3600
if {[findclass
[HTTP::uri] $::old_server_pool " "] ne "" } {
pool old_server_pool-80
} elseif {[findclass [HTTP::uri]
$::new_server_pool " "] ne "" } {
pool new_server_pool-8001
}
}
It is not working as I thought
it would. The web servers are doing a
redirect from VIPIP/APP1/login.html to VIPIP/psp/APP1/?cmd=login. I have to put the redirect URI in the data group
instead of the original URI. Why isn’t
the original URI evaluated? Is there a better way of doing this?
- The_BhattmanHi Patrick,
can you post the structure of your data group?
Bhattman 
Michael_YatesI think that it might be because you are using findclass instead of matchclass.
In your example you are saying:
If the [HTTP::uri] is equal to a value that I have stored in my data group, replace that value with the second data group value. If that value is not equal to "" nothing, then direct traffic to pool "old_server_pool-80.
findclass is best used for a Match and Replace.
Searches a data group list for a member whose key matches the specified string, and if a match is found, returns the data-group member string.
http://devcentral.f5.com/wiki/default.aspx/iRules/findclass.html
Try matchclass:when HTTP_REQUEST { if { [matchclass [HTTP::uri] equals $::old_server_pool] } { pool old_server_pool-80 } elseif { [matchclass [HTTP::uri] equals $::new_server_pool] } { pool new_server_pool-8001 } }
Patrick_McGlyn1Sure. I should have thought to include it. I started with the following:
class old_server_pool {
"/app1/login.html"
}
I had to change it to the redirect URL to get it to work.
class old_server_pool {
"/psp/app1/?cmd=login"
}- Patrick_McGlyn1Michael,
Thanks for the information. I tried the matchclass and it didn't work. I logged the URI before it hits the if statement. It is being logged as the redirected URI.
log local0. "uri_string is => [HTTP::uri]"
Result:
Jun 15 17:25:14 tmm tmm[700]: Rule test-pool-select-irule : uri_string is => /psp/app1/?cmd=login
I am not sure why. - The_BhattmanHi Patrick,
From what I can tell you could do the followingclass redirectapp { "/app1/login.html /psp/app1/?cmd=login" "/app2/login.html /psp/app2/?cmd=login" "/app3/login.html /psp/app3/?cmd=login" }when HTTP_REQUEST { set uriredirected [findclass [string tolower[HTTP::uri]] $::redirectapp " "] if {$uriredirected ne "" } { HTTP::redirect "http://www.domain.com/$uriredirected" pool new_server_pool-8001 } }
This means if someone enters
http://something.com/app1/login.html it will be redirected to /psp/app1/?cmd=logi
or if someone enters
http://something.com/app2/login.html it will be redirected to /psp/app2/?cmd=logi
or if someone enters
http://something.com/app3/login.html it will be redirected to /psp/app3/?cmd=logi
is this what were looking for?
Bhattman - The_BhattmanMade a correction on the code
when HTTP_REQUEST { switch -glob [string tolower [HTTP::uri] { "/psp/app*" { pool new_server_pool-8001 } default { set redirectapp [findclass [string tolower[HTTP::uri]] $::redirectapp " "] if {$redirectapp ne "" } { HTTP::redirect "http://www.domain.com/$redirectapp" } } } }
Bhattman - Patrick_McGlyn1Thanks Bhattman. I think it should work but I am still confused. Why does the URI show up in the log as the redirect URI received from the web server and not the original URI enter by the client?
I thought I would see the URI as /app1/login.html if https://VIPIP/app1/login.html was entered in the browser instead of /psp/app1/?cmd=login which is the redirected URI sent back by the web server.
