load-balancer-config

Reconfiguring a Load Balancer Without Dropping Connections

Changing load balancer routing rules on a live system risks dropping connections if you apply the config before discovering all backends. This workflow discovers 6 backend servers, configures weighted round-robin routing rules, applies the configuration without connection drops, and verifies all backends are healthy with traffic flowing.

Workflow

loadBalancer, algorithm
          |
          v
+-----------------------+     +----------------------+     +------------------+     +------------------+
| lb_discover_backends  | --> | lb_configure_rules   | --> | lb_apply_config  | --> | lb_health_check  |
+-----------------------+     +----------------------+     +------------------+     +------------------+
  DISCOVER_BACKENDS-1354       weighted round-robin         applied without          all backends
  6 backend servers            rules updated                connection drops         healthy

Workers

DiscoverBackendsWorker -- Takes the loadBalancer name and discovers 6 backend servers. Returns discover_backendsId: "DISCOVER_BACKENDS-1354".

ConfigureRulesWorker -- Updates routing rules to weighted round-robin. Returns configure_rules: true.

ApplyConfigWorker -- Applies the configuration without dropping existing connections. Returns apply_config: true.

HealthCheckWorker -- Verifies all backends are healthy and traffic is flowing. Returns health_check: true with a completedAt timestamp.

Tests

17 unit tests cover backend discovery, rule configuration, config application, and health checks.

Running

See ../../RUNNING.md for setup and execution instructions.