Add prometheus serializer and use it in prometheus output (#6703)

plugins/outputs/prometheus_client/v2/collector.go

@@ -0,0 +1,87 @@
+package v2
+
+import (
+	"sync"
+	"time"
+
+	"github.com/influxdata/telegraf"
+	serializer "github.com/influxdata/telegraf/plugins/serializers/prometheus"
+	"github.com/prometheus/client_golang/prometheus"
+	dto "github.com/prometheus/client_model/go"
+)
+
+type Metric struct {
+	family *dto.MetricFamily
+	metric *dto.Metric
+}
+
+func (m *Metric) Desc() *prometheus.Desc {
+	labelNames := make([]string, 0, len(m.metric.Label))
+	for _, label := range m.metric.Label {
+		labelNames = append(labelNames, *label.Name)
+	}
+
+	desc := prometheus.NewDesc(*m.family.Name, *m.family.Help, labelNames, nil)
+
+	return desc
+}
+
+func (m *Metric) Write(out *dto.Metric) error {
+	out.Label = m.metric.Label
+	out.Counter = m.metric.Counter
+	out.Untyped = m.metric.Untyped
+	out.Gauge = m.metric.Gauge
+	out.Histogram = m.metric.Histogram
+	out.Summary = m.metric.Summary
+	out.TimestampMs = m.metric.TimestampMs
+	return nil
+}
+
+type Collector struct {
+	sync.Mutex
+	expireDuration time.Duration
+	coll           *serializer.Collection
+}
+
+func NewCollector(expire time.Duration, stringsAsLabel bool) *Collector {
+	config := serializer.FormatConfig{}
+	if stringsAsLabel {
+		config.StringHandling = serializer.StringAsLabel
+	}
+	return &Collector{
+		expireDuration: expire,
+		coll:           serializer.NewCollection(config),
+	}
+}
+
+func (c *Collector) Describe(ch chan<- *prometheus.Desc) {
+	// Sending no descriptor at all marks the Collector as "unchecked",
+	// i.e. no checks will be performed at registration time, and the
+	// Collector may yield any Metric it sees fit in its Collect method.
+	return
+}
+
+func (c *Collector) Collect(ch chan<- prometheus.Metric) {
+	c.Lock()
+	defer c.Unlock()
+
+	for _, family := range c.coll.GetProto() {
+		for _, metric := range family.Metric {
+			ch <- &Metric{family: family, metric: metric}
+		}
+	}
+}
+
+func (c *Collector) Add(metrics []telegraf.Metric) error {
+	c.Lock()
+	defer c.Unlock()
+
+	for _, metric := range metrics {
+		c.coll.Add(metric)
+	}
+
+	if c.expireDuration != 0 {
+		c.coll.Expire(time.Now(), c.expireDuration)
+	}
+	return nil
+}