Forum Discussion

adminas

Altocumulus

Jul 10, 2024

Need help with iRule based on host and path

Hello all.

I am trying to create an iRule that will choose a specific pool based on host and path. I tried the following code:

when HTTP_REQUEST {
if { [HTTP::host] equals "hostname_a"} {
if { [HTTP::path] equals "/path" } {

pool pool_a
log local0. "URL : [HTTP::host][HTTP::uri] entered"
}
}
if { [HTTP::host] equals "hostname_b"} {
if { [HTTP::path] equals "/path" } {

pool pool_b
log local0. "URL : [HTTP::host][HTTP::uri] entered"
}
}
}

According to Big-IP stats, the iRule gets executed but it doesnot direct the call to the pool (pool stats shows 0) specified although logging is invoked and I get the URL in the ltm logs.

Right after this script there is another one which gets executed and works as it should be. It specifies even more conditions for a series of pools and if none is matched then directs the call to the default pool specified there.

The problem is with the first one. I would like it to be executed and unless there is a match, then it should proceed to executing the second one.

If you can give me some advice it would be highly appreciated. Thank you.

application delivery

load balacing

adminas
Jul 11, 2024
Finally, problem solved! The reason was the order of execution for the 2 scripts. I donot really understand why this happens but when I placed the script in second place, everything is executed as expected. If you have any ideas please let me know.
The problematic order which doesnot work is shown below:
First script:
when HTTP_REQUEST {
if { [HTTP::host] equals "hostname_a"} {
if { [HTTP::path] equals "/path" } {
pool pool_a
log local0. "URL : [HTTP::host][HTTP::uri] entered"
}
}
if { [HTTP::host] equals "hostname_b"} {
if { [HTTP::path] equals "/path" } {
pool pool_b
log local0. "URL : [HTTP::host][HTTP::uri] entered"
}
}
}

Second script:
when HTTP_REQUEST {
if {[HTTP::has_responded]}{return}
switch -glob [string tolower [HTTP::path]]
{
....
....
    }
    default
{
switch [string tolower [HTTP::host]]
{
                 "hostname_a"
                 {
pool pool_c
   persist none
                  }
....
.....
                  default
                   {
                         pool_z
                   }
......
Anyway, thank you all very much for your time.

adminas
Altocumulus
Jul 11, 2024
Finally, problem solved! The reason was the order of execution for the 2 scripts. I donot really understand why this happens but when I placed the script in second place, everything is executed as expected. If you have any ideas please let me know.
The problematic order which doesnot work is shown below:
First script:
when HTTP_REQUEST {
if { [HTTP::host] equals "hostname_a"} {
if { [HTTP::path] equals "/path" } {
pool pool_a
log local0. "URL : [HTTP::host][HTTP::uri] entered"
}
}
if { [HTTP::host] equals "hostname_b"} {
if { [HTTP::path] equals "/path" } {
pool pool_b
log local0. "URL : [HTTP::host][HTTP::uri] entered"
}
}
}

Second script:
when HTTP_REQUEST {
if {[HTTP::has_responded]}{return}
switch -glob [string tolower [HTTP::path]]
{
....
....
    }
    default
{
switch [string tolower [HTTP::host]]
{
                 "hostname_a"
                 {
pool pool_c
   persist none
                  }
....
.....
                  default
                   {
                         pool_z
                   }
......
Anyway, thank you all very much for your time.
JoseLabra
MVP
Jul 10, 2024
Hii how r u?

Why you dont use a Policy? Its more simple

check this article
https://my.f5.com/manage/s/article/K15097
adminas
Altocumulus
Jul 10, 2024
Hi. I am fine and hope the same for you!
Thank you very much for your reply but the are already 3 working iRules that I cannot remove / convert and I need just an extra iRule to be executed in the beggining and move to the next script if no match is found. Its a production system and I cannot really experiment as I have no experience in policies.
- JoseLabra
  MVP
  Jul 10, 2024
  And if you captured the traffic with tcpdump and test the iRule, you see the LB correctly?
  I remember a scenario with the same issue, the pool dont show the stats, but the LB its working.
  
  if was the case, open a ticket to support for more detail
  - adminas
    Altocumulus
    Jul 11, 2024
    Thank you.. I tried with tcpdump -nnvvi but cannot see any request going to the pool specified. I can see only health checking.
- zamroni777
  Nacreous
  Jul 10, 2024
  "equals" means exact match.
  maybe what you need is starts_with.
  https://clouddocs.f5.com/api/irules/starts_with.html
  for testing, you can install virtualedition with trial license or create test vserver
  - adminas
    Altocumulus
    Jul 11, 2024
    Thank you for your suggestion but there is no change.
Aswin_mk
Cumulonimbus
Jul 10, 2024
Can u try with below example, u can add specific uri and host name. u can edit it based on your different host and path

when HTTP_REQUEST {
# Define pool selection based on host and path
if { [HTTP::host] eq "example.com" } {
if { [HTTP::uri] starts_with "/app1" } {
pool pool_app1
} elseif { [HTTP::uri] starts_with "/app2" } {
pool pool_app2
} else {
pool default_pool
}
} elseif { [HTTP::host] eq "anotherexample.com" } {
if { [HTTP::uri] starts_with "/service1" } {
pool pool_service1
} elseif { [HTTP::uri] starts_with "/service2" } {
pool pool_service2
} else {
pool default_pool
}
} else {
# Fallback to a default pool if no match is found
pool default_pool
}
}
- adminas
  Altocumulus
  Jul 11, 2024
  Thank you. Tried it, same result.
Aswin_mk
Cumulonimbus
Jul 11, 2024
Good adminas.thanks for the confirmation 🙂