Liberica

Liberica is the next-generation load balancer replacing PyBal. It is designed with a modular approach and written in Go. The source code is available on GitLab.

Daemons

Control Plane

The control plane (cp) daemon orchestrates the rest of the Liberica daemons. It uses a configuration file to define a list of services and relies on etcd for real server discovery. Communication with other Liberica daemons and gobgpd occurs over gRPC.

Forwarding Plane

The forwarding plane (fp) daemon exposes the following forwarding planes to Liberica’s control plane via its gRPC API:

IPVS
Katran

Healthcheck Forwarder

The healthcheck forwarder (hcforwarder) daemon forwards health check traffic to real servers in the same way production traffic reaches them (using IPIP encapsulation). It consists of two components: a Go daemon that exposes a gRPC API and Prometheus metrics, and an eBPF program that handles the network traffic. The healthcheck daemon targets a specific real server by setting a SOMARK. The hcforwarder uses this SOMARK to identify the real server's IP and perform IPIP encapsulation.

Healthcheck

The Liberica healthcheck daemon performs health checks and tracks their results. It notifies subscribers (usually the control plane daemon) of any changes in the state of real servers. Additionally, it exposes health check results as Prometheus metrics.

Operating Liberica

Liberica provides a CLI tool called liberica for fetching the current state of its various daemons. This tool uses the same gRPC API employed by the Liberica control plane daemon to gather insights from different components.