Adding upstream version 1.34.4.

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

plugins/inputs/vsphere/tscache.go

@@ -0,0 +1,61 @@
+package vsphere
+
+import (
+	"sync"
+	"time"
+
+	"github.com/influxdata/telegraf"
+)
+
+// tsCache is a cache of timestamps used to determine the validity of datapoints
+type tsCache struct {
+	ttl   time.Duration
+	table map[string]time.Time
+	mux   sync.RWMutex
+	log   telegraf.Logger
+}
+
+// newTSCache creates a new tsCache with a specified time-to-live after which timestamps are discarded.
+func newTSCache(ttl time.Duration, log telegraf.Logger) *tsCache {
+	return &tsCache{
+		ttl:   ttl,
+		table: make(map[string]time.Time),
+		log:   log,
+	}
+}
+
+// purge removes timestamps that are older than the time-to-live
+func (t *tsCache) purge() {
+	t.mux.Lock()
+	defer t.mux.Unlock()
+	n := 0
+	for k, v := range t.table {
+		if time.Since(v) > t.ttl {
+			delete(t.table, k)
+			n++
+		}
+	}
+	t.log.Debugf("purged timestamp cache. %d deleted with %d remaining", n, len(t.table))
+}
+
+// get returns a timestamp (if present)
+func (t *tsCache) get(key, metricName string) (time.Time, bool) {
+	t.mux.RLock()
+	defer t.mux.RUnlock()
+	ts, ok := t.table[makeKey(key, metricName)]
+	return ts, ok
+}
+
+// put updates the latest timestamp for the supplied key.
+func (t *tsCache) put(key, metricName string, timestamp time.Time) {
+	t.mux.Lock()
+	defer t.mux.Unlock()
+	k := makeKey(key, metricName)
+	if timestamp.After(t.table[k]) {
+		t.table[k] = timestamp
+	}
+}
+
+func makeKey(resource, metric string) string {
+	return resource + "|" + metric
+}