haproxy

Start HAProxy

$ haproxy -f [/etc/haproxy/haproxy.cfg]

$ haproxy -c -f [/etc/haproxy/haproxy.cfg]

$ haproxy -f [config.cfg] -sf $(pidof haproxy)

$ haproxy -D -f [config.cfg]

$ haproxy -v

haproxy [options] -f config

HAProxy (High Availability Proxy) is a high-performance TCP/HTTP load balancer and reverse proxy that distributes incoming traffic across pools of backend servers. Its configuration is organized around frontends (which accept client connections on bound addresses and ports) and backends (which define the set of servers that handle requests, along with the balancing algorithm -- round-robin, least-connections, source-hash, and others). Active health checks continuously probe backend servers and automatically remove unhealthy nodes from rotation.
Beyond basic load balancing, HAProxy provides SSL/TLS termination, HTTP header manipulation, content-based routing via ACLs, connection rate limiting, stick tables for session persistence, and a real-time statistics dashboard. It operates in an event-driven, single-process architecture that can handle hundreds of thousands of concurrent connections with low latency and minimal resource consumption, making it a standard choice for high-traffic production environments.

-f file

Configuration file.

Check configuration and exit.

Daemon mode.

Soft-stop old processes.

Hard-stop old processes.

PID file path.

Maximum connections.

Default per-proxy maxconn.

Debug mode.

Verbose mode.

Configuration changes require reload. Complex ACLs need careful testing. Statistics require separate configuration. SSL setup needs certificate management.

HAProxy was created by Willy Tarreau in 2000 and has become one of the most widely deployed load balancers. It powers high-traffic sites including GitHub, Reddit, and Stack Overflow.

nginx(1), envoy(1), traefik(1)