MySQL active connection never bleed off to other pool member

Virtual Server

create ltm virtual /OSTACK/OSTACK_VS_GALERA { destination 172.28.0.9:3306 ip-protocol tcp mask 255.255.255.255 pool /OSTACK/OSTACK_POOL_GALERA profiles replace-all-with { /Common/fastL4 { } }  mirror enabled source-address-translation { pool /OSTACK/OSTACK_SNATPOOL type snat } }

POOL

create ltm pool /OSTACK/OSTACK_POOL_GALERA { load-balancing-mode least-connections-node members replace-all-with { OSTACK_NODE_ostack-infra-02_galera_container-fa5d9e98:3306 { priority-group 100 } OSTACK_NODE_ostack-infra-03_galera_container-eaacd880:3306 { priority-group 95 } OSTACK_NODE_ostack-infra-01_galera_container-6c126d29:3306 { priority-group 90 } } min-active-members 1 service-down-action reset slow-ramp-time 0 monitor /OSTACK/OSTACK_MON_GALERA }