106 lines
2.1 KiB
Go
106 lines
2.1 KiB
Go
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package cpu
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import (
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"bufio"
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"os"
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"strconv"
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"strings"
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"bugs.watch/agent/internal/aggregate"
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)
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type Sample struct {
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Idle uint64
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Total uint64
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}
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// ReadSample reads CPU counters from /proc/stat.
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// It returns cumulative counters since boot.
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func ReadSample() (Sample, error) {
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f, err := os.Open("/proc/stat")
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if err != nil {
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return Sample{}, err
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}
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defer f.Close()
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scanner := bufio.NewScanner(f)
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if !scanner.Scan() {
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if err := scanner.Err(); err != nil {
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return Sample{}, err
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}
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return Sample{}, strconv.ErrSyntax
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}
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// First line:
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// cpu user nice system idle iowait irq softirq steal guest guest_nice
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fields := strings.Fields(scanner.Text())
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if len(fields) < 5 || fields[0] != "cpu" {
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return Sample{}, strconv.ErrSyntax
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}
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var total uint64
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for i := 1; i < len(fields); i++ {
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v, err := strconv.ParseUint(fields[i], 10, 64)
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if err != nil {
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return Sample{}, err
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}
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total += v
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}
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idle, err := strconv.ParseUint(fields[4], 10, 64)
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if err != nil {
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return Sample{}, err
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}
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return Sample{Idle: idle, Total: total}, nil
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}
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// UsagePercent computes CPU usage percentage between two samples.
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func UsagePercent(prev, curr Sample) float64 {
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// Guard against counter resets or weirdness
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if curr.Total <= prev.Total || curr.Idle < prev.Idle {
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return 0
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}
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idleDelta := curr.Idle - prev.Idle
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totalDelta := curr.Total - prev.Total
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if totalDelta == 0 {
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return 0
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}
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usedDelta := totalDelta - idleDelta
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return (float64(usedDelta) / float64(totalDelta)) * 100.0
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}
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// Collector implements a stateful CPU usage collector.
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// It stores the previous sample internally so the agent does not have to.
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type Collector struct {
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prev Sample
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hasPrev bool
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}
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func New() *Collector {
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return &Collector{}
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}
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func (c *Collector) Name() string {
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return "cpu"
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}
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// Collect reads current CPU counters and, if possible, emits a usage percent.
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// On first run it will not emit (no previous sample yet).
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func (c *Collector) Collect(window *aggregate.Window) {
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curr, err := ReadSample()
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if err != nil {
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return
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}
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if c.hasPrev {
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usage := UsagePercent(c.prev, curr)
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window.AddCPU(usage)
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}
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c.prev = curr
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c.hasPrev = true
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}
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