[FAB-12516] GetBlock: Close() ledger iterator

This change set ensures the ledger iterator is closed
in GetBlock method

Change-Id: I294cfe1ba94a6f11b266184f01a30be6c5780dff
Signed-off-by: yacovm <yacovm@il.ibm.com>

common/ledger/blockledger/util.go

@@ -79,12 +79,16 @@ func CreateNextBlock(rl Reader, messages []*cb.Envelope) *cb.Block {
 
 // GetBlock is a utility method for retrieving a single block
 func GetBlock(rl Reader, index uint64) *cb.Block {
-	i, _ := rl.Iterator(&ab.SeekPosition{
+	iterator, _ := rl.Iterator(&ab.SeekPosition{
 		Type: &ab.SeekPosition_Specified{
 			Specified: &ab.SeekSpecified{Number: index},
 		},
 	})
-	block, status := i.Next()
+	if iterator == nil {
+		return nil
+	}
+	defer iterator.Close()
+	block, status := iterator.Next()
 	if status != cb.Status_SUCCESS {
 		return nil
 	}

common/ledger/blockledger/util_test.go

@@ -0,0 +1,55 @@
+/*
+Copyright IBM Corp. All Rights Reserved.
+
+SPDX-License-Identifier: Apache-2.0
+*/
+
+package blockledger_test
+
+import (
+	"testing"
+
+	"github.com/hyperledger/fabric/common/deliver/mock"
+	"github.com/hyperledger/fabric/common/ledger/blockledger"
+	"github.com/hyperledger/fabric/protos/common"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestClose(t *testing.T) {
+	for _, testCase := range []struct {
+		name               string
+		status             common.Status
+		isIteratorNil      bool
+		expectedCloseCount int
+	}{
+		{
+			name:          "nil iterator",
+			isIteratorNil: true,
+		},
+		{
+			name:               "Next() fails",
+			status:             common.Status_INTERNAL_SERVER_ERROR,
+			expectedCloseCount: 1,
+		},
+		{
+			name:               "Next() succeeds",
+			status:             common.Status_SUCCESS,
+			expectedCloseCount: 1,
+		},
+	} {
+		t.Run(testCase.name, func(t *testing.T) {
+			var iterator *mock.BlockIterator
+			reader := &mock.BlockReader{}
+			if !testCase.isIteratorNil {
+				iterator = &mock.BlockIterator{}
+				iterator.NextReturns(&common.Block{}, testCase.status)
+				reader.IteratorReturns(iterator, 1)
+			}
+
+			blockledger.GetBlock(reader, 1)
+			if !testCase.isIteratorNil {
+				assert.Equal(t, testCase.expectedCloseCount, iterator.CloseCallCount())
+			}
+		})
+	}
+}