The module is experimental. It is actively developed and its features and API might significantly change in the future.

The module implements an improved (relative to the standard L2 mode in MetalLB) balancing mechanism for services in bare metal clusters when there is no option to use cloud load balancers or MetalLB in BGP mode with Equal-cost multi-path (ECMP) configured.

Based on MetalLB solution.

Principle of operation compared to L2 mode in MetalLB module

MetalLB in L2 mode allows for provision a Service of the LoadBalancer type, the operation of which is based on the fact that balancing nodes simulate ARP responses from the “public” IP in a peering network. This mode has a significant limitation — only one balancing node handles all the incoming traffic of this service at a time. Therefore:

  • The node selected as the leader for the “public” IP becomes a “bottleneck” with no possibility of horizontal scaling.
  • If the balancer node fails, all current connections will be dropped for switching to a new balancing node that will be selected as the leader.

This module helps bypass these limitations. It provides a new L2LoadBalancer interface that:

  • Allows to automatically order multiple Service with type LoadBalancer according to the number of balancer nodes.
  • Provides an even distribution of L2 leadership among the balancer nodes.

Thus:

  • The application will receive not a single, but several (according to the number of balancer nodes) “public” IPs. These IPs will need to be configured as A-records for the application’s public domain. For further horizontal scaling, additional balancer nodes will need to be added, the corresponding Service will be created automatically, you just need to add them to the list of A-records for the application domain.
  • If one of the balancer nodes fails, only a part of the connections will be prone to failover to the healthy node.