haproxy_backends.cfg

backend main
    balance roundrobin
    cookie SERVERID insert indirect nocache maxlife 2h
    option forwardfor
    option http-server-close
    option http-pretend-keepalive
    timeout queue 5000
    timeout connect 5000
    timeout server 50000
    server old-service-old-pg old-service.eu-west-1.elasticbeanstalk.com:80 weight 128 cookie old_v1 check
    server new-service-new-pg new-service.eu-west-1.elasticbeanstalk.com:80 weight 128 cookie new_v1 check

backend old_service
    option forwardfor
    option http-server-close
    option http-pretend-keepalive
    timeout queue 5000
    timeout connect 5000
    timeout server 50000
    server old-service-old-pg-static old-service.eu-west-1.elasticbeanstalk.com:80 check

backend new_service
    option forwardfor
    option http-server-close
    option http-pretend-keepalive
    timeout queue 5000
    timeout connect 5000
    timeout server 50000
    server new-service-new-pg-static new-service.eu-west-1.elasticbeanstalk.com:80 check