Forum Discussion
NimbostratusTraffic experience during during a Default Pool change.
I have a need to change the default pool on an active VIP.
What is the experience of the traffic while the change is happening...what's going on behind the scenes when I click the update button?
Will the traffic that's inflight just finish to the existing pool setting and as the new pool value is being applied requests flow until the new pool is in the active config and then requests flow to the new pool? What happens to the existing cached connections...do they get issued a RST? How much impact do I need to plan for? Will inflight requests get dropped causing my application to error?
Any help would be appreciated...I understand changes to iRules and other certain changes use the old value until the new value is saved/loaded and then the next request uses the new value, but what about the default pool (the only pool used).
2 Replies
What_Lies_Bene1Cirrostratus
Err, it depends. In nearly all cases the original value is used so in the case of any existing (or new persisted connections related to them) connections, they will go to the old Pool. It depends because;
1) OneConnect changes this behaviour as it makes a load balancing decision for HTTP traffic per request
2) Priority Group Activation may muddy the picture
3) If we're talking UDP and you have Datagram LB each packet is load balanced individually
4) iRule may also muddy the picture
fubarSUSHIAltocumulus
I would recommend adding the new members in the pool and "disable" (will keep active and persistent connections) the old members. In this case, when you know there isnt any new traffic (by checking stats) you can remove the old pool members from the same pool group.
I have done it the other way by swapping pools and we did notice a few errors but nothing that had a "smoking gun" error that I could find from doing so...
