Limit the number of goroutines used for the update of ingress status

vendor/gopkg.in/go-playground/pool.v3/work_unit.go

@@ -0,0 +1,77 @@
+package pool
+
+import "sync/atomic"
+
+// WorkUnit contains a single uint of works values
+type WorkUnit interface {
+
+	// Wait blocks until WorkUnit has been processed or cancelled
+	Wait()
+
+	// Value returns the work units return value
+	Value() interface{}
+
+	// Error returns the Work Unit's error
+	Error() error
+
+	// Cancel cancels this specific unit of work, if not already committed
+	// to processing.
+	Cancel()
+
+	// IsCancelled returns if the Work Unit has been cancelled.
+	// NOTE: After Checking IsCancelled(), if it returns false the
+	// Work Unit can no longer be cancelled and will use your returned values.
+	IsCancelled() bool
+}
+
+var _ WorkUnit = new(workUnit)
+
+// workUnit contains a single unit of works values
+type workUnit struct {
+	value      interface{}
+	err        error
+	done       chan struct{}
+	fn         WorkFunc
+	cancelled  atomic.Value
+	cancelling atomic.Value
+	writing    atomic.Value
+}
+
+// Cancel cancels this specific unit of work, if not already committed to processing.
+func (wu *workUnit) Cancel() {
+	wu.cancelWithError(&ErrCancelled{s: errCancelled})
+}
+
+func (wu *workUnit) cancelWithError(err error) {
+
+	wu.cancelling.Store(struct{}{})
+
+	if wu.writing.Load() == nil && wu.cancelled.Load() == nil {
+		wu.cancelled.Store(struct{}{})
+		wu.err = err
+		close(wu.done)
+	}
+}
+
+// Wait blocks until WorkUnit has been processed or cancelled
+func (wu *workUnit) Wait() {
+	<-wu.done
+}
+
+// Value returns the work units return value
+func (wu *workUnit) Value() interface{} {
+	return wu.value
+}
+
+// Error returns the Work Unit's error
+func (wu *workUnit) Error() error {
+	return wu.err
+}
+
+// IsCancelled returns if the Work Unit has been cancelled.
+// NOTE: After Checking IsCancelled(), if it returns false the
+// Work Unit can no longer be cancelled and will use your returned values.
+func (wu *workUnit) IsCancelled() bool {
+	wu.writing.Store(struct{}{}) // ensure that after this check we are committed as cannot be cancelled if not aalready
+	return wu.cancelled.Load() != nil
+}