admin: add in-memory metrics series store

Bounded ring buffer (240 samples) keyed by source/metric[/labels],
reusing the dashSample ring pattern. No persistence; powers the
upcoming monitoring charts.

weed/admin/dash/metrics_store.go

@@ -0,0 +1,117 @@
+package dash
+
+import (
+	"sync"
+	"time"
+)
+
+const metricsMaxSamples = 240
+
+type metricsSample struct {
+	t      time.Time
+	values map[string]float64
+}
+
+type metricsSeries struct {
+	mu      sync.Mutex
+	samples []metricsSample
+}
+
+func newMetricsSeries() *metricsSeries {
+	return &metricsSeries{samples: make([]metricsSample, 0, metricsMaxSamples)}
+}
+
+func (s *metricsSeries) record(t time.Time, values map[string]float64) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	s.samples = append(s.samples, metricsSample{t: t, values: values})
+	if len(s.samples) > metricsMaxSamples {
+		s.samples = s.samples[len(s.samples)-metricsMaxSamples:]
+	}
+}
+
+func (s *metricsSeries) snapshot() []metricsSample {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	out := make([]metricsSample, len(s.samples))
+	copy(out, s.samples)
+	return out
+}
+
+type metricsStore struct {
+	mu      sync.Mutex
+	series  map[string]*metricsSeries
+}
+
+func newMetricsStore() *metricsStore {
+	return &metricsStore{series: make(map[string]*metricsSeries)}
+}
+
+func (s *metricsStore) record(source, name string, value float64, t time.Time) {
+	s.mu.Lock()
+	key := source + "/" + name
+	ser, ok := s.series[key]
+	if !ok {
+		ser = newMetricsSeries()
+		s.series[key] = ser
+	}
+	s.mu.Unlock()
+	ser.record(t, map[string]float64{"": value})
+}
+
+func (s *metricsStore) recordLabeled(source, name string, labels map[string]string, value float64, t time.Time) {
+	s.mu.Lock()
+	key := source + "/" + name + "/" + labelKey(labels)
+	ser, ok := s.series[key]
+	if !ok {
+		ser = newMetricsSeries()
+		s.series[key] = ser
+	}
+	s.mu.Unlock()
+	ser.record(t, map[string]float64{"": value})
+}
+
+func (s *metricsStore) get(source, name string) []metricsSample {
+	s.mu.Lock()
+	key := source + "/" + name
+	ser, ok := s.series[key]
+	s.mu.Unlock()
+	if !ok {
+		return nil
+	}
+	return ser.snapshot()
+}
+
+func (s *metricsStore) getLabeled(source, name string, labels map[string]string) []metricsSample {
+	s.mu.Lock()
+	key := source + "/" + name + "/" + labelKey(labels)
+	ser, ok := s.series[key]
+	s.mu.Unlock()
+	if !ok {
+		return nil
+	}
+	return ser.snapshot()
+}
+
+func labelKey(labels map[string]string) string {
+	if len(labels) == 0 {
+		return ""
+	}
+	keys := make([]string, 0, len(labels))
+	for k := range labels {
+		keys = append(keys, k)
+	}
+	for i := 1; i < len(keys); i++ {
+		for j := i; j > 0 && keys[j] < keys[j-1]; j-- {
+			keys[j], keys[j-1] = keys[j-1], keys[j]
+		}
+	}
+	out := ""
+	for i, k := range keys {
+		if i > 0 {
+			out += ","
+		}
+		out += k + "=" + labels[k]
+	}
+	return out
+}