Cloud Service Mesh Spot Vm Resilience Automatic Capacity

What Preferred Backends and Automatic Capacity Draining Are

Preferred backends allow Cloud Service Mesh to prioritize routing traffic to specific compute resources—such as cost-effective Spot VM Managed Instance Groups (MIGs)—until their capacity is fully utilized before spilling over to non-preferred backends (such as standard on-demand VMs). Automatic capacity draining is an advanced traffic management feature that automatically scales a backend's effective capacity down to zero when less than 25% of its instances or endpoints pass health checks.

How It Meets the Requirements

• Protects surviving instances from cascading failures: When Spot VM preemption causes instances to terminate and fall below the 25% health check threshold, automatic capacity draining immediately isolates the degraded MIG by setting its capacity scaler to zero, preventing the few surviving instances from taking on the entire zone's load.
• Optimizes FinOps cost savings: Designating Spot VM MIGs as preferred backends ensures that cheaper Spot compute is maximized during normal steady-state operation.
• Ensures graceful spillover and failover: Traffic exceeding Spot capacity or diverted due to capacity draining is automatically shifted to non-preferred, on-demand fallback MIGs without service disruption.

Key Advantages and Capabilities

• Automated recovery: When the MIG recovers and at least 35% of its endpoints remain healthy for 60 seconds, Cloud Service Mesh automatically restores (undrains) traffic to the backend.
• Built-in safety limits: Cloud Service Mesh enforces safety controls so it will never drain more than 50% of endpoints across the entire backend service simultaneously.
• Native mesh integration: Eliminates the need for custom external scripts or webhook automation during mass preemption events.

Why This Is Optimal

Combining preferred backends with automatic capacity draining establishes an automated, resilient FinOps architecture where cost-optimized Spot VMs are prioritized while eliminating the risk of traffic bottlenecks during sudden preemption surges.