Forum Discussion
BIG-IP : iRule to route uri-forms for all hosts
F5 BIG-IP Virtual Edition v11.4.1 (Build 635.0) LTM on ESXi
My BIG-IP is configued with virtual-servers specific to hostname :
VIP-1 handles www.example1.com VIP-2 handles www.example2.com
DNS routes www.example1.com to VIP-1 IP and www.example2.com to VIP-2 IP
For all hostnames, I need to route certain uri-forms to a an alternate traffic-manager ( pool_alt_tm ).
My idea is to create a single iRule and add it to VIP-1 and VIP-2.
Here's my iRule :
when HTTP_REQUEST {
set route_to_alt_tm 0
switch -glob [string tolower [HTTP::uri]] {
"/best-pool*" - "/best-bar*" - "/most-romantic*" {
set route_to_alt_tm 1
}
"/about/termsandconditions.html" - "/about/yourpersonalinfo.html" - "/about/rewards.html" {
set route_to_alt_tm 1
}
}
if {$route_to_alt_tm} {
pool pool_alt_tm
event disable all
}
}
Are there any potential problems with not explicitly checking that request host matches www.example1.com --or-- www.example2.com ?
Any drawbacks to this approach ?
Michael_JenkinsCirrostratus
I don't think there's any potential problems here with not checking the Host name. It just means that if someone's accessing the site by IP address or using something like a hosts file, it'll still processes the traffic the same way.
On another note, with the
command, all further iRule processing will be cancelled for the life of that connection, not just the that particular request necessarily. (Just wanted to mention that since I had a few issues when I first started using that command). Is that what you're trying to do? or perhaps just ignore further HTTP_REQUEST events for that request?event disable allThanks again Michael. In my case, the goal is for certain uri-forms to be routed to an entirely separate traffic-manager ( custom code built around HAProxy ) which performs all further handling of the request. I'm not at all sure about this, but I believe the other traffic-manager sends its responses directly to the client -- I don't believe responses flow back through BIG-IP ( is this even possible ? I need to research and find out for sure ). If so, BIG-IP will never have opportunity to execute HTTP_RESPONSE event. Subsequent requests on the same keep-alive connection should be processed anew -- because might be a request for a different uri that may or may not be contained in the set of uri-forms routed to the other traffic-manager.
- Michael_JenkinsIf that's the case (response skips the BIG-IP), then you may consider using a variable in your iRule and checking it in any other HTTP_REQUEST events to skip processing them. Another option in that case might be to disable events and then use `event HTTP_REQUEST_RELEASE enable` and re-enable all events (`event enable all`) in the release event, which may work for subsequent requests. To test whether the traffic is coming back through the F5, you could use `tcpdump` through the CLI and grab the traffic to see if it's getting any responses from the server.
- turns out I was mistaken -- the alt-tm response traffic does flow back through the F5 on its way to client
Santokn_189503Nimbostratus
Hi Baltostar
From the above irule i understood (Correct me if i am wrong as i am new to irule) that if the below URI matches
"/best-pool" - "/best-bar" - "/most-romantic*" "/about/termsandconditions.html" - "/about/yourpersonalinfo.html" - "/about/rewards.html"
Set the variable route_to_alt_tm to 1 and also if route_to_alt_tm is equal to 1 then choose the pool pool_alt_tm
Could me please post the complete irule and explanations also bit confuse reg. the need for set route_to_alt_tm 0
- Michael_Jenkinsthe "set route_to_alt_tm 0" command is used so that when checking the variable for "1", it won't give a runtime error because the variable is not defined. The other option if you don't know whether a variable has been set is to use "[info exists VARNAME]"
- Santokn_189503
Thanks Michael
However i couldnt able to understand the below suggestions which u gave earlier, Can u please explain me with an example.
but you may want to use "event disable all" in your HTTP_REQUEST, and then right after use "event HTTP_RESPONSE enable" to allow the response event to fire. You can also set a flag (variable) to tell your response event to disable processing too. In your HTTP_RESPONSE event (make sure this would be the first one that executes), you can check for that variable (you can test if a variable exists with "[info exists VARIABLE_NAME]") and then do "event enable all", "event HTTP_RESPONSE disable", and "return" to exit the iRule
