Configuration File Structure#

HAProxy uses a single configuration file, typically /etc/haproxy/haproxy.cfg. The configuration is divided into four sections: global (process-level settings), defaults (default values for all proxies), frontend (client-facing listeners), and backend (server pools).

global
    log /dev/log local0
    log /dev/log local1 notice
    maxconn 50000
    user haproxy
    group haproxy
    daemon
    stats socket /run/haproxy/admin.sock mode 660 level admin
    tune.ssl.default-dh-param 2048

defaults
    log     global
    mode    http
    option  httplog
    option  dontlognull
    timeout connect 5s
    timeout client  30s
    timeout server  30s
    timeout http-request 10s
    timeout http-keep-alive 10s
    errorfile 400 /etc/haproxy/errors/400.http
    errorfile 403 /etc/haproxy/errors/403.http
    errorfile 500 /etc/haproxy/errors/500.http
    errorfile 502 /etc/haproxy/errors/502.http
    errorfile 503 /etc/haproxy/errors/503.http

The maxconn in the global section sets the hard limit on total simultaneous connections. The timeout values in defaults apply to all frontends and backends unless overridden. The stats socket directive enables the runtime API, which is essential for operational management.