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Balancer

Balancers are responsible for selecting a backend for a given request or connection. They sit between processors and proxies.

WRR (Weighted Round-Robin) Balancer

The wrr balancer distributes traffic among backends according to a weight determined by an HCL expression. It uses a Smooth Weighted Round-Robin algorithm (similar to NGINX) and is implemented with a lock-free design for maximum performance.

balancer "wrr" "my_balancer" {
  source = backends_processor.simple_filter.healthy_nodes
  weight = int(backend.meta.consul_kv.weight)
  timeout = "5s"
}
  • source (string, required): The ID of the backend provider (inventory or processor).
  • weight (HCL expression, required): An expression that evaluates to an integer representing the weight of the backend. Higher weights receive more traffic.
  • timeout (duration string, optional): If the balancer has no available backends, it will wait up to this duration for a backend to become available before failing. Default: 0s.

WLC (Weighted Least Connections) Balancer

The wlc balancer selects the backend with the lowest number of active connections relative to its weight. It is ideal for protocols with long-lived connections like TCP.

balancer "wlc" "my_balancer" {
  source = backends_processor.simple_filter.healthy_nodes
  weight = int(backend.meta.consul_kv.weight)
  timeout = "5s"
}
  • source (string, required): The ID of the backend provider.
  • weight (HCL expression, required): An expression that evaluates to an integer. The balancer selects the backend minimizing active_connections / weight.
  • timeout (duration string, optional): Duration to wait for a backend if none are available. Default: 0s.