GLB: GitHub's open source load balancer

This post details the design and open-sourcing of GLB, GitHub's Layer 4 load balancer. It explains how GLB uses ECMP routing and rendezvous hashing to scale a single IP address across multiple physical machines while minimizing connection disruption during server changes. The GLB Director tier is stateless, forwarding packets to primary and secondary servers based on a pre-computed forwarding table, which provides a 'second chance' mechanism for connections. The post also contrasts GLB's approach with traditional LVS director designs and discusses the invariants maintained by rendezvous hashing for consistent server selection.