Method collectSnapshot

pkg/wshrpc/wshremote/processviewer.go:246–353

collectSnapshot fetches all process info, updates lastCPUSamples with fresh measurements, and computes CPU% using each pid's previous sample (if available).

(numCPU int)

// collectSnapshot fetches all process info, updates lastCPUSamples with fresh measurements,
// and computes CPU% using each pid's previous sample (if available).
func (s *procCacheState) collectSnapshot(numCPU int) *wshrpc.ProcessListResponse {
	ctx, cancel := context.WithTimeout(context.Background(), 8*time.Second)
	defer cancel()

	procs, err := goproc.ProcessesWithContext(ctx)
	if err != nil {
		return nil
	}

	if s.lastCPUSamples == nil {
		s.lastCPUSamples = make(map[int32]cpuSample, len(procs))
	}

	snap, err := procinfo.MakeGlobalSnapshot()
	if err != nil {
		return nil
	}

	hasCPU := s.lastCPUEpoch > 1 // first epoch has no previous sample to diff against

	type pidInfo struct {
		pid  int32
		info *procinfo.ProcInfo
	}
	rawInfos := make([]pidInfo, len(procs))
	for i, p := range procs {
		pi, err := procinfo.GetProcInfo(ctx, snap, p.Pid)
		if err != nil {
			pi = nil
		}
		rawInfos[i] = pidInfo{pid: p.Pid, info: pi}
	}

	// Sample CPU times and compute CPU% sequentially to keep epoch accounting simple.
	cpuPcts := make(map[int32]float64, len(procs))
	sampleTime := time.Now()
	for _, ri := range rawInfos {
		if ri.info == nil {
			continue
		}
		if ri.info.CpuUser < 0 || ri.info.CpuSys < 0 {
			continue
		}
		curCPUSec := ri.info.CpuUser + ri.info.CpuSys

		if hasCPU {
			if prev, ok := s.lastCPUSamples[ri.pid]; ok {
				elapsed := sampleTime.Sub(prev.SampledAt).Seconds()
				if elapsed > 0 {
					cpuPcts[ri.pid] = computeCPUPct(prev.CPUSec, curCPUSec, elapsed)
				}
			}
		}

		s.lastCPUSamples[ri.pid] = cpuSample{
			CPUSec:    curCPUSec,
			SampledAt: sampleTime,
			Epoch:     s.lastCPUEpoch,