container_common.go

package checks

import (
	"time"
)

func calculateCtrPct(cur, prev float64, sys2, sys1 uint64, numCPU int, current, before time.Time) float32 {
	// -1 is returned if a cgroup file is missing or the `ContainerCPUStats` object is nil.
	// In these situations, return -1 so that the metric is skipped on the backend.
	if cur == -1 || prev == -1 {
		return -1
	}
	diff := current.Sub(before).Seconds()
	if before.IsZero() || diff < 0 {
		return 0
	}

	// Prevent uint underflows
	if prev > cur || sys1 > sys2 {
		return 0
	}

	cpuDelta := cur - prev

	// If we have system usage values then we need to calculate against those.
	// XXX: Right now this only applies to ECS collection. Note that the inclusion of CPUs is
	// necessary because the value gets normalized against the CPU limit, which also accounts for CPUs.
	if sys1 >= 0 && sys2 > 0 && sys2 != sys1 {
		sysDelta := float64(sys2 - sys1)
		return float32((cpuDelta / sysDelta) * float64(numCPU) * 100)
	}

	return float32(cpuDelta / diff)
}