$ curl "http://127.0.0.1:6000/dynamic?upstream=zone_for_backends"
server 127.0.0.1:6001;
server 127.0.0.1:6002;
server 127.0.0.1:6003;
$

$ curl "http://127.0.0.1:6000/dynamic?upstream=zone_for_backends&verbose="
server 127.0.0.1:6001 weight=1 max_fails=1 fail_timeout=10;
server 127.0.0.1:6002 weight=1 max_fails=1 fail_timeout=10;
server 127.0.0.1:6003 weight=1 max_fails=1 fail_timeout=10;
$

$ curl "http://127.0.0.1:6000/dynamic?upstream=zone_for_backends&server=127.0.0.1:6003&weight=10&max_fails=5&fail_timeout=5"
server 127.0.0.1:6001 weight=1 max_fails=1 fail_timeout=10;
server 127.0.0.1:6002 weight=1 max_fails=1 fail_timeout=10;
server 127.0.0.1:6003 weight=10 max_fails=5 fail_timeout=5;
$

$ curl "http://127.0.0.1:6000/dynamic?upstream=zone_for_backends&server=127.0.0.1:6003&down="
server 127.0.0.1:6001 weight=1 max_fails=1 fail_timeout=10;
server 127.0.0.1:6002 weight=1 max_fails=1 fail_timeout=10;
server 127.0.0.1:6003 weight=1 max_fails=1 fail_timeout=10 down;
$

$ curl "http://127.0.0.1:6000/dynamic?upstream=zone_for_backends&server=127.0.0.1:6003&up="
server 127.0.0.1:6001 weight=1 max_fails=1 fail_timeout=10;
server 127.0.0.1:6002 weight=1 max_fails=1 fail_timeout=10;
server 127.0.0.1:6003 weight=1 max_fails=1 fail_timeout=10;
$

$ curl "http://127.0.0.1:6000/dynamic?upstream=zone_for_backends&add=&server=127.0.0.1:6004"
server 127.0.0.1:6001;
server 127.0.0.1:6002;
server 127.0.0.1:6003;
server 127.0.0.1:6004;
$