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Global Load Balancer (GLB)

Overview

The Global Load Balancer (GLB) provides multi-region traffic distribution at the DNS level. Unlike regional load balancers that operate at the network layer within a VPC, GLB utilizes GeoDNS to steer users to the optimal regional endpoint based on policies like latency, health, and weight.

Features

  • Global Traffic Steering: Route traffic across multiple regions.
  • Health-Aware Routing: Automatically removes unhealthy regional endpoints from DNS resolution.
  • Policy-Based Distribution:
    • Latency: Directs users to the region with the lowest network latency.
    • Geolocation: Routes traffic based on the user's geographic location.
    • Weighted: Distributes traffic proportionally across regions.
    • Failover: Priority-based failover for disaster recovery.
  • Unified Hostname: Provide a single global hostname for your application (e.g., api.global.example.com).

Architecture

GLB follows the standard hexadecimal architecture of the platform:

  1. Service Layer: Handles the business logic of GLB creation, endpoint management, and synchronization with DNS.
  2. GeoDNS Adapter: Communicates with the authoritative DNS server (PowerDNS) to update records in real-time.
  3. Repository: Stores metadata in PostgreSQL about GLB configurations and endpoint health status.

Configuration

Health Checks

GLB performs synthesized health checks from multiple points of presence. Configuration includes:

  • Protocol: HTTP, HTTPS, or TCP.

  • Port: The destination port to probe.

  • Interval: Frequency of probes (default 30s).

  • Thresholds: Number of consecutive successes/failures to change health status.

  • Regional Load Balancers: Linked by ID to existing platform resource. Security: GLB verifies that the regional LB belongs to the same user.

  • External IPs: Arbitrary static IPs for hybrid-cloud scenarios.

Security & Multi-tenancy

GLB is a multi-tenant service. Security is enforced at several layers:

  • Data Isolation: Users can only see and manage Global Load Balancers they have created. List and Get operations are scoped to the authenticated user's ID.
  • Resource Ownership Verification: When adding a Regional Load Balancer as an endpoint, the system verifies that the target LB belongs to the user attempting to add it. This prevents unauthorized traffic steering of other users' resources.

Resource Synchronization

The service ensures that the authoritative DNS state always reflects the database state:

  • Transactional Consistency: Changes in the database are followed by immediate synchronization calls to the GeoDNS backend.
  • Removal Logic: Deleting an endpoint or the entire GLB automatically triggers the removal of associated DNS records, preventing orphaned routing entries.

API Usage

Create a GLB:

cloud global-lb create --name "prod-api" --hostname "api.global.com" --policy "LATENCY"

Add a regional endpoint:

cloud global-lb add-endpoint --id <glb-id> --region "us-east-1" --target-ip "1.2.3.4" --weight 100