Improve scalability of vsphere input (#5113)

plugins/inputs/vsphere/throttled_exec.go

@@ -0,0 +1,45 @@
+package vsphere
+
+import (
+	"context"
+	"sync"
+)
+
+// ThrottledExecutor provides a simple mechanism for running jobs in separate
+// goroutines while limit the number of concurrent jobs running at any given time.
+type ThrottledExecutor struct {
+	limiter chan struct{}
+	wg      sync.WaitGroup
+}
+
+// NewThrottledExecutor creates a new ThrottlesExecutor with a specified maximum
+// number of concurrent jobs
+func NewThrottledExecutor(limit int) *ThrottledExecutor {
+	if limit == 0 {
+		panic("Limit must be > 0")
+	}
+	return &ThrottledExecutor{limiter: make(chan struct{}, limit)}
+}
+
+// Run schedules a job for execution as soon as possible while respecting the
+// maximum concurrency limit.
+func (t *ThrottledExecutor) Run(ctx context.Context, job func()) {
+	t.wg.Add(1)
+	go func() {
+		defer t.wg.Done()
+		select {
+		case t.limiter <- struct{}{}:
+			defer func() {
+				<-t.limiter
+			}()
+			job()
+		case <-ctx.Done():
+			return
+		}
+	}()
+}
+
+// Wait blocks until all scheduled jobs have finished
+func (t *ThrottledExecutor) Wait() {
+	t.wg.Wait()
+}