Home / server / Questions / 930422
In Process
Tarwin
Asked: 2018-09-12 05:35:08 +0800 CST

HAProxy: Use saved state to restore backend IPs possible?

  • 772

We are using HAProxy 1.8.13 on Centos 7 with dynamically assigned backends (backend IPs and ports assigned over stats socket). This works fine.

We need a method to make the dynamically assigned stuff stick over restarts and wanted to use the "load-server-state-from-file" directive. Sadly we are running into an error (or maybe its by design?) that the state file does not restore the configured IP address:

Our test config: 

global
    log         127.0.0.1 local2
    chroot      /var/lib/haproxy
    pidfile     /var/run/haproxy.pid
    maxconn     4000
    user        haproxy
    group       haproxy
    daemon
    nbproc      2
    stats socket /run/haproxy/1.sock mode 0744 level admin process 1
    stats socket /run/haproxy/2.sock mode 0744 level admin process 2
    server-state-file /run/haproxy/server_state

defaults
    load-server-state-from-file global
    timeout server 10s
    timeout client 15s
    timeout queue 6s
    timeout connect 10s

frontend  main
    bind *:5000
    default_backend             app

backend app
    balance     roundrobin
    server  app1 127.0.0.1:5001 check
    server  app2 127.0.0.1:5002 check
    server  app3 127.0.0.1:5003 check
    server  app4 127.0.0.1:5004 check

We are configuring the IPs via script and then saving the state with: 

echo "show servers state" | socat /run/haproxy/1.sock - > /run/haproxy/server_state

Which produces for example: 

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
7 app 1 app1 127.0.0.1 0 1 1 1 60 8 2 0 14 0 0 0 - 5001
7 app 2 app2 10.10.10.115 2 0 1 1 23 6 3 4 6 0 0 0 - 31501
7 app 3 app3 10.10.10.113 2 0 1 1 22 6 3 4 6 0 0 0 - 31375
7 app 4 app4 10.10.10.114 2 0 1 1 22 6 3 4 6 0 0 0 - 31400

When haproxy restarts it restores up/down state information and port, but resets the IP to 127.0.0.1: 

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
7 app 1 app1 127.0.0.1 0 1 1 1 7 8 2 0 14 0 0 0 - 5001
7 app 2 app2 127.0.0.1 0 0 1 1 2 8 2 0 6 0 0 0 - 31501
7 app 3 app3 127.0.0.1 0 0 1 1 2 8 2 0 6 0 0 0 - 31375
7 app 4 app4 127.0.0.1 0 0 1 1 1 8 2 0 6 0 0 0 - 31400

We toyed around with "init-addr" but this only affects DNS based backend addresses. Do we do something wrong? It this expected behavior? Or is this some kind of bug?

haproxy

1 Answers

  1. We found out it works when we replace '127.0.0.1' with 'localhost'.

    HAProxy seems to ignore backend IPs in the state file, at least with the versions we tested (1.8.7, 1.8.13, 1.9-dev). Backend servers that have DNS names as configured default do get the IPs from the state file applied.

    We took a deep dive in the code and opened a bug with a patch on the HAProxy ML here.

    • 1