(Host is unreachable) What's that mean?

It seams haproxy said “localhost” unreachable? just start my haproxy, no other op

/root# docker-compose up --build
Starting haproxy ... done
Attaching to haproxy
haproxy    | [NOTICE]   (1) : New worker #1 (8) forked
haproxy    | be_app4test/srv1 changed its FQDN from (null) to localhost by 'SRV record'
haproxy    | be_app4test/srv1 changed its IP from (none) to ::1 by ldns/dns1.
haproxy    | Server be_app4test/srv1 ('localhost') is UP/READY (resolves again).
haproxy    | Server be_app4test/srv1 administratively READY thanks to valid DNS answer.
haproxy    | [WARNING]  (8) : be_app4test/srv1 changed its IP from (none) to ::1 by ldns/dns1.
haproxy    | [WARNING]  (8) : Server be_app4test/srv1 ('localhost') is UP/READY (resolves again).
haproxy    | [WARNING]  (8) : Server be_app4test/srv1 administratively READY thanks to valid DNS answer.
haproxy    | [WARNING]  (8) : Server be_app4test/srv1 is DOWN, reason: Layer4 connection problem, info: "General socket error (Host is unreachable)", check duration: 0ms. 0 active and 0 backup servers left. 0 sessions active, 0 requeued, 0 remaining in queue.
haproxy    | [NOTICE]   (8) : haproxy version is 2.4.7-b5e51a5
haproxy    | [ALERT]    (8) : backend 'be_app4test' has no server available!
haproxy    | Server be_app4test/srv1 is DOWN, reason: Layer4 connection problem, info: "General socket error (Host is unreachable)", check duration: 0ms. 0 active and 0 backup servers left. 0 sessions active, 0 requeued, 0 remaining in queue.
haproxy    | backend be_app4test has no server available!
/run # echo "show servers state" | socat stdio ./haproxy-svc1.sock
1
# be_id be_name srv_id srv_name srv_addr srv_op_state srv_admin_state srv_uweight srv_iweight srv_time_since_last_change srv_check_status srv_check_result srv_check_health srv_check_state srv_agent_state bk_f_forced_id srv_f_forced_id srv_fqdn srv_port srvrecord
4 be_app4test 1 srv1 ::1 0 64 1 1 882 8 2 0 6 0 0 0 localhost 36065 _app4test._tcp.h5.lc

It means the health checks towards the IPv6 address ::1 failed, because it could not reach the destination service.

Thank you for point out that, I truely can’t access it via ipv6, after edit /etc/sysctl.conf, it’s ok.
thanks again :sweat_smile: