[LB::server pool] evaluation changes between HTTP_REQUEST and HTTP_REQUEST_SEND

Question

Consider a virtual server with two pools, one for virtual host A and one for virtual host B:

https://A.example.com/ --> pool_A
https://B.example.com/ --> pool_B

We are using a Local Traffic Policy to perform pool selection.
We have a client-side HTTP/2 profile attached to this virtual server.
We are using TMOS 16.1.4.
We do not have OneConnect enabled.

When I browse to site A and check "[LB::server pool]" in HTTP_REQUEST, it evaluates to "pool_A". In HTTP_REQUEST_SEND, "[LB::server pool]" also evaluates to "pool_A". This is to be expected…

However, when I then browse to site B and check "[LB::server pool]" in HTTP_REQUEST, I still get "pool_A"???

In the corresponding HTTP_REQUEST_SEND event, "[LB::server pool]" does correctly evaluates to "pool_B". (Also: in the corresponding LB_SELECTED event, "[LB::server pool]" correctly evaluates to "pool_B".)

Somewhere between HTTP_REQUEST and LB_SELECTED/HTTP_REQUEST_SEND, the value of "[LB::server pool]" changes from "pool_A" to "pool_B". This is NOT what I would expect...

If I remove the HTTP/2 client-side profile, this behaviour is not observed (and "[LB::server pool]" evaluates to the same pool in both the HTTP_REQUEST and LB_SELECTED/HTTP_REQUEST_SEND event).

Has anyone observed this behaviour before? Is this a 'bug' perhaps?

zamroni777 · Answer

how is the persistence setting?is it cookie or something else?i suggest you use gui based traffic policy instead of irules.https://community.f5.com/t5/technical-articles/to-irule-or-not-to-irule-introduction-to-local-traffic-policies/ta-p/279536&nbsp;

frank_ten_wolde · Answer

No, we're not using persistence, nor cookies. And we are using LTPs to do the pool selection.

Also, I wouldn't expect the "LB::server pool" to change between the HTTP_REQUEST and LB_SELECTED/HTTP_REQUEST_SEND events...

zamroni777 · Answer

I test using below irules and found that LB_SELECTED happens before HTTP_REQUEST.so it seems that's why in HTTP_REQUEST you still get pool_A when traffic policy config should select pool_B.&nbsp;when LB_SELECTED {
log local0. "CCCCCCCCC"
}

when  HTTP_REQUEST  {
log local0. "BBBBBBBBBBBBB"
}

when  HTTP_REQUEST_SEND  {
log local0. "AAAAAAAAAAAAAAA"
}&nbsp;&nbsp;

Forum Discussion

[LB::server pool] evaluation changes between HTTP_REQUEST and HTTP_REQUEST_SEND

Recent Discussions

010713d0:3: Symmetric Unit Key decrypt failure - decrypt failure Rseries Tenant ..

Help with Migrating Netscaler Rewrite Policy to F5 LTM

Need to change HTML tag in HTTP response

Rewriting Location Header in iRule

Outlook application issue

Related Content

iRules how to make the http_request seeping ip

SSL::PROFILE in HTTP_REQUEST

F5 Intelligent DNS Services Demo 1: Server LB, Visibility and Control

CACHE_RESPONSE to HTTP_REQUEST

timeouts on specific http_request