[#901] util: implement Release for PseudWorkerPool

Signed-off-by: Evgenii Stratonikov <evgeniy@nspcc.ru>

pkg/util/worker_pool_test.go

@@ -0,0 +1,52 @@
+package util
+
+import (
+	"sync"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestSyncWorkerPool(t *testing.T) {
+	t.Run("submit to released pool", func(t *testing.T) {
+		p := NewPseudoWorkerPool()
+		p.Release()
+		require.Equal(t, ErrPoolClosed, p.Submit(func() {}))
+	})
+	t.Run("create and wait", func(t *testing.T) {
+		p := NewPseudoWorkerPool()
+		ch1, ch2 := make(chan struct{}), make(chan struct{})
+		wg := new(sync.WaitGroup)
+		wg.Add(2)
+		go func(t *testing.T) {
+			defer wg.Done()
+			err := p.Submit(newControlledReturnFunc(ch1))
+			require.NoError(t, err)
+		}(t)
+		go func(t *testing.T) {
+			defer wg.Done()
+			err := p.Submit(newControlledReturnFunc(ch2))
+			require.NoError(t, err)
+		}(t)
+
+		// Make sure functions were submitted.
+		<-ch1
+		<-ch2
+		p.Release()
+		require.Equal(t, ErrPoolClosed, p.Submit(func() {}))
+
+		close(ch1)
+		close(ch2)
+		wg.Wait()
+	})
+}
+
+// newControlledReturnFunc returns function which signals in ch after
+// it has started and waits for some value in channel to return.
+// ch must be unbuffered.
+func newControlledReturnFunc(ch chan struct{}) func() {
+	return func() {
+		ch <- struct{}{}
+		<-ch
+	}
+}