Overview
The Xloud Load Balancer service uses a controller-appliance model. The controller manages the lifecycle of load balancing appliances and translates API requests into configuration. The appliance processes all data-plane traffic — the controller does not handle production traffic. Understanding this architecture is essential for capacity planning, HA configuration, and troubleshooting.Service Topology
Component Reference
| Component | Description |
|---|---|
| LB Controller | Translates API requests into appliance configuration. Manages appliance lifecycle. Does not handle production traffic. |
| Appliance | A virtual machine instance running the load balancing software. Processes all data-plane traffic. Created per load balancer resource. |
| Service DB | MariaDB database storing load balancer resource state (listeners, pools, members, health monitors). |
| Message Queue | RabbitMQ queue for decoupled communication between the API and controller components. |
| Management Network | Dedicated network connecting the controller to appliances for configuration and health management. Isolated from tenant networks. |
Data Plane vs Management Plane
Data plane
Data plane
The data plane carries production application traffic from clients to backend members.
All data plane traffic flows through the appliance instance directly:
- Client → Floating IP → Appliance VIP → Backend Member
- The controller is not in the data path
- Appliance failure = service interruption (use ACTIVE_STANDBY topology for HA)
Management plane
Management plane
The management plane carries control traffic between the controller and appliances:
- Configuration updates (new listeners, pool changes, member additions)
- Health probe coordination
- Appliance certificate management and renewal
- TLS certificates on the management network prevent unauthorized appliance access
High Availability Topologies
| Topology | Description | Use Case |
|---|---|---|
SINGLE | One appliance instance per load balancer | Development and testing |
ACTIVE_STANDBY | Active appliance + hot standby. Failover in seconds | Production workloads |
Deployment Considerations
Management network sizing
Management network sizing
The management network must provide enough IP addresses for all appliance instances
plus spare capacity for concurrent provisioning. Size the management network DHCP
pool at
(max concurrent LBs) × 2 + 10 addresses.Compute resources for appliances
Compute resources for appliances
Each load balancer appliance is a virtual machine consuming compute resources.
In large deployments, ensure sufficient compute capacity is reserved for appliance
instances. Consider a dedicated host aggregate for load balancer appliances.
Next Steps
Provider Drivers
Configure the underlying load balancing implementation.
Flavor Profiles
Define appliance capacity tiers including HA topology selection.
Monitoring
Monitor appliance health and management plane connectivity.
Security
Secure the management network and appliance certificate lifecycle.