server with active connection goes down

[Avinish Pathak1709161001]

Just want to understand the situation when one of the backend server goes down which have active sessions on it.

 

Does the Netscaler gracefully move it to other back-end server or it will just terminates it??

 

Just for your info, i have SSL session persistence type configured on VIP.

 

Please suggest.

[Diego Oliveira]

 If the client and the load-balanced server should renegotiate the session ID during their transactions, persistence is not maintained, and a new persistence session is created when the client’s next request is received.

https://docs.citrix.com/en-us/netscaler/12/load-balancing/load-balancing-persistence/session-id-persistence.html

[Rhonda Rowland1709152125]

To expand on what Diego said.  It depends on what type of "down"

If the service is "out of service" because it reaches a max threshold or you manually "disable" the service gracefully, then as long as "down state flush" is disabled, then existing transactions will complete, but no new transactions will be sent that service.  New load balancing/persistence decisions will be made for relevant transactions.  If "down state flush" is enabled, then all existing transactions end on current service and will be forced to start on new one. See here:  https://support.citrix.com/article/CTX124710

 

If the service is "down" because it is offline/unavailable, then it is not possible to allow existing transactions to complete.  And as Diego noted, any "persistence" against the "down" service will be discarded for a new persistence decision as the current persistence cannot be honored.

 

For your original question, the netscaler can only "move" a request to a new destination during the next request decision.  So a service going offline mid-transaction may impact that particular transaction, but the user's next request will be load balanced appropriately.