Making Facebook’s software infrastructure more energy efficient with Autoscale

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Introduced Autoscale, a power-efficient load balancing system for Facebook web clusters. Autoscale dynamically adjusts the active server pool to concentrate workload onto a subset of servers during low-traffic periods, ensuring each active server maintains at least medium-level CPU utilization. This approach avoids running servers at low RPS, which is power-inefficient, and instead allows idle servers to be powered down or repurposed for batch processing. The system uses a feedback loop control mechanism with PI controllers and modeled relationships between CPU utilization and requests-per-second to determine the optimal active pool size. Preliminary results showed up to 27% power savings around midnight and an average of 10-15% over a 24-hour cycle in production web clusters.