Adding upstream version 1.34.4.

Signed-off-by: Daniel Baumann <daniel@debian.org>

metric/deserialize.go

@@ -0,0 +1,85 @@
+package metric
+
+import (
+	"bytes"
+	"encoding/gob"
+	"errors"
+	"fmt"
+	"sync"
+
+	"github.com/influxdata/telegraf"
+)
+
+// storage for tracking data that can't be serialized to disk
+var (
+	// grouped tracking metrics means that ID->Data association is not one to one,
+	// many metrics could be associated with one tracking ID so we cannot just
+	// clear this every time in FromBytes.
+	trackingStore = make(map[telegraf.TrackingID]telegraf.TrackingData)
+	mu            = sync.Mutex{}
+
+	// ErrSkipTracking indicates that tracking information could not be found after
+	// deserializing a metric from bytes. In this case we should skip the metric
+	// and continue as if it does not exist.
+	ErrSkipTracking = errors.New("metric tracking data not found")
+)
+
+type serializedMetric struct {
+	M   telegraf.Metric
+	TID telegraf.TrackingID
+}
+
+func ToBytes(m telegraf.Metric) ([]byte, error) {
+	var sm serializedMetric
+	if um, ok := m.(telegraf.UnwrappableMetric); ok {
+		sm.M = um.Unwrap()
+	} else {
+		sm.M = m
+	}
+
+	if tm, ok := m.(telegraf.TrackingMetric); ok {
+		sm.TID = tm.TrackingID()
+
+		mu.Lock()
+		trackingStore[sm.TID] = tm.TrackingData()
+		mu.Unlock()
+	}
+
+	var buf bytes.Buffer
+	encoder := gob.NewEncoder(&buf)
+	if err := encoder.Encode(&sm); err != nil {
+		return nil, fmt.Errorf("failed to encode metric to bytes: %w", err)
+	}
+	return buf.Bytes(), nil
+}
+
+func FromBytes(b []byte) (telegraf.Metric, error) {
+	buf := bytes.NewBuffer(b)
+	decoder := gob.NewDecoder(buf)
+
+	var sm *serializedMetric
+	if err := decoder.Decode(&sm); err != nil {
+		return nil, fmt.Errorf("failed to decode metric from bytes: %w", err)
+	}
+
+	m := sm.M
+	if sm.TID != 0 {
+		mu.Lock()
+		td := trackingStore[sm.TID]
+		if td == nil {
+			mu.Unlock()
+			return nil, ErrSkipTracking
+		}
+		rc := td.RefCount()
+		if rc <= 1 {
+			// only 1 metric left referencing this tracking ID, we can remove here since no subsequent metrics
+			// read can use this ID. If another metric in a metric group with this ID gets added later, it will
+			// simply be added back into the tracking store again.
+			trackingStore[sm.TID] = nil
+		}
+		mu.Unlock()
+
+		m = rebuildTrackingMetric(m, td)
+	}
+	return m, nil
+}