https://confluence.atlassian.com/enterprise/jira-data-center-load-balancer-examples-781200827.html

In your example:

backend bk_web
   balance roundrobin
   cookie JSESSIONID prefix indirect nocache
   server s1 backend1: 8090  check cookie s1
   server s2 backend2: 8090  check cookie s2

Using indirect with prefix causes problems with WebSudo.

Note: it is highly recommended not to use “indirect” with
“prefix”, otherwise server cookie updates would not be sent to
clients.

Reference: http://blog.haproxy.com/2012/03/29/load-balancing-affinity-persistence-sticky-sessions-what-you-need-to-know/