[FAB-12508] Add Block(seq) to consenter support

This change set adds a method that retrieves a block from
the ledger in the consenter support.

Change-Id: Id088ec688e169d306c242352b485a8e47809b7db
Signed-off-by: yacovm <yacovm@il.ibm.com>

common/ledger/blockledger/ledger.go

@@ -48,6 +48,8 @@ type Writer interface {
 	Append(block *cb.Block) error
 }
 
+//go:generate mockery -dir . -name ReadWriter -case underscore  -output mocks/
+
 // ReadWriter encapsulates the read/write functions of the ledger
 type ReadWriter interface {
 	Reader

orderer/common/multichannel/chainsupport.go

@@ -73,6 +73,15 @@ func newChainSupport(
 	return cs
 }
 
+// Block returns a block with the following number,
+// or nil if such a block doesn't exist.
+func (cs *ChainSupport) Block(number uint64) *cb.Block {
+	if cs.Height() <= number {
+		return nil
+	}
+	return blockledger.GetBlock(cs.Reader(), number)
+}
+
 func (cs *ChainSupport) Reader() blockledger.Reader {
 	return cs
 }

orderer/common/multichannel/chainsupprt_test.go

@@ -0,0 +1,33 @@
+/*
+Copyright IBM Corp. All Rights Reserved.
+
+SPDX-License-Identifier: Apache-2.0
+*/
+
+package multichannel
+
+import (
+	"testing"
+
+	"github.com/hyperledger/fabric/common/deliver/mock"
+	"github.com/hyperledger/fabric/common/ledger/blockledger/mocks"
+	"github.com/hyperledger/fabric/protos/common"
+	"github.com/hyperledger/fabric/protos/orderer"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestChainSupportBlock(t *testing.T) {
+	ledger := &mocks.ReadWriter{}
+	ledger.On("Height").Return(uint64(100))
+	iterator := &mock.BlockIterator{}
+	iterator.NextReturns(&common.Block{Header: &common.BlockHeader{Number: 99}}, common.Status_SUCCESS)
+	ledger.On("Iterator", &orderer.SeekPosition{
+		Type: &orderer.SeekPosition_Specified{
+			Specified: &orderer.SeekSpecified{Number: 99},
+		},
+	}).Return(iterator, uint64(99))
+	cs := &ChainSupport{ledgerResources: &ledgerResources{ReadWriter: ledger}}
+
+	assert.Nil(t, cs.Block(100))
+	assert.Equal(t, uint64(99), cs.Block(99).Header.Number)
+}

orderer/consensus/consensus.go

@@ -84,6 +84,10 @@ type ConsenterSupport interface {
 	// Note that either WriteBlock or WriteConfigBlock must be called before invoking this method a second time.
 	CreateNextBlock(messages []*cb.Envelope) *cb.Block
 
+	// Block returns a block with the following number,
+	// or nil if such a block doesn't exist.
+	Block(number uint64) *cb.Block
+
 	// WriteBlock commits a block to the ledger.
 	WriteBlock(block *cb.Block, encodedMetadataValue []byte)
 

orderer/consensus/kafka/chain_test.go

@@ -3634,6 +3634,11 @@ type mockConsenterSupport struct {
 	mock.Mock
 }
 
+func (c *mockConsenterSupport) Block(seq uint64) *cb.Block {
+	// TODO: implement this
+	return nil
+}
+
 func (c *mockConsenterSupport) NewSignatureHeader() (*cb.SignatureHeader, error) {
 	args := c.Called()
 	return args.Get(0).(*cb.SignatureHeader), args.Error(1)

orderer/mocks/common/multichannel/multichannel.go

@@ -62,6 +62,11 @@ type ConsenterSupport struct {
 	SequenceVal uint64
 }
 
+func (mcs *ConsenterSupport) Block(seq uint64) *cb.Block {
+	// TODO: implement this
+	return nil
+}
+
 // BlockCutter returns BlockCutterVal
 func (mcs *ConsenterSupport) BlockCutter() blockcutter.Receiver {
 	return mcs.BlockCutterVal