metrics have been added

1 files changed, 36 insertions, 0 deletions

diff --git a/library/go/x/xsync/singleinflight.go b/library/go/x/xsync/singleinflight.go
new file mode 100644
index 0000000000..3beee1ea67
--- /dev/null
+++ b/library/go/x/xsync/singleinflight.go
@@ -0,0 +1,36 @@
+package xsync
+
+import (
+	"sync"
+	"sync/atomic"
+)
+
+// SingleInflight allows only one execution of function at time.
+// For more exhaustive functionality see https://pkg.go.dev/golang.org/x/sync/singleflight.
+type SingleInflight struct {
+	updatingOnce atomic.Value
+}
+
+// NewSingleInflight creates new SingleInflight.
+func NewSingleInflight() SingleInflight {
+	var v atomic.Value
+	v.Store(new(sync.Once))
+	return SingleInflight{updatingOnce: v}
+}
+
+// Do executes the given function, making sure that only one execution is in-flight.
+// If another caller comes in, it waits for the original to complete.
+func (i *SingleInflight) Do(f func()) {
+	i.getOnce().Do(func() {
+		f()
+		i.setOnce()
+	})
+}
+
+func (i *SingleInflight) getOnce() *sync.Once {
+	return i.updatingOnce.Load().(*sync.Once)
+}
+
+func (i *SingleInflight) setOnce() {
+	i.updatingOnce.Store(new(sync.Once))
+}