HAProxy Fundamentals

HAProxy sits between clients and application servers. A client connects to HAProxy. HAProxy accepts that connection, applies the configured policy, and opens or uses a connection to a backend server.

This position gives HAProxy one clear job: control traffic before it reaches your application fleet. You can distribute work, route requests by HTTP information, terminate TLS, check server health, and keep unavailable servers out of rotation.

The mental model

Treat the configuration as a traffic path.

1. A frontend owns one or more listening sockets through bind.
2. The frontend selects a backend, either as its default or through a conditional rule.
3. The backend contains named server entries and a balancing policy.
4. HAProxy selects an eligible server and proxies the traffic.