[FAB-8900] random max targets for config block

Chconfig currently fetches config block from all
configured peers. change has been made to select
max random targets from low level chconfig opts.

TO DO: The number of peers also need to be exposed as option
in higher level clients or in config.

Change-Id: Ib94fb3ec96291e8af0a5bcdb38f3c3d9655407b2
Signed-off-by: Sudesh Shetty <sudesh.shetty@securekey.com>

pkg/fab/chconfig/chconfig.go

@@ -8,6 +8,7 @@ package chconfig
 
 import (
 	reqContext "context"
+	"math/rand"
 
 	"github.com/golang/protobuf/proto"
 
@@ -33,13 +34,15 @@ var logger = logging.NewLogger("fabsdk/fab")
 
 const (
 	defaultMinResponses = 1
+	defaultMaxTargets   = 2
 )
 
 // Opts contains options for retrieving channel configuration
 type Opts struct {
 	Orderer      fab.Orderer // if configured, channel config will be retrieved from this orderer
 	Targets      []fab.Peer  // if configured, channel config will be retrieved from peers (targets)
 	MinResponses int         // used with targets option; min number of success responses (from targets/peers)
+	MaxTargets   int         //if configured, channel config will be retrieved for these number of random targets
 }
 
 // Option func for each Opts argument
@@ -145,18 +148,15 @@ func (c *ChannelConfig) queryPeers(reqCtx reqContext.Context) (*ChannelCfg, erro
 			}
 
 			targets = append(targets, newPeer)
-
 		}
+
+		targets = randomMaxTargets(targets, c.opts.MaxTargets)
+
 	} else {
 		targets = peersToTxnProcessors(c.opts.Targets)
 	}
 
-	minEndorsers := c.opts.MinResponses
-	if minEndorsers == 0 {
-		minEndorsers = defaultMinResponses
-	}
-
-	configEnvelope, err := l.QueryConfigBlock(reqCtx, targets, minEndorsers)
+	configEnvelope, err := l.QueryConfigBlock(reqCtx, targets, c.opts.MinResponses)
 	if err != nil {
 		return nil, errors.WithMessage(err, "QueryBlockConfig failed")
 	}
@@ -198,6 +198,14 @@ func WithOrderer(orderer fab.Orderer) Option {
 	}
 }
 
+// WithMaxTargets encapsulates minTargets to Option
+func WithMaxTargets(maxTargets int) Option {
+	return func(opts *Opts) error {
+		opts.MaxTargets = maxTargets
+		return nil
+	}
+}
+
 // prepareQueryConfigOpts Reads channel config options from Option array
 func prepareOpts(options ...Option) (Opts, error) {
 	opts := Opts{}
@@ -207,6 +215,15 @@ func prepareOpts(options ...Option) (Opts, error) {
 			return opts, errors.WithMessage(err, "Failed to read query config opts")
 		}
 	}
+
+	//resolve defaults
+	if opts.MinResponses == 0 {
+		opts.MinResponses = defaultMinResponses
+	}
+	if opts.MaxTargets == 0 {
+		opts.MaxTargets = defaultMaxTargets
+	}
+
 	return opts, nil
 }
 
@@ -481,3 +498,15 @@ func peersToTxnProcessors(peers []fab.Peer) []fab.ProposalProcessor {
 	}
 	return tpp
 }
+
+//randomMaxTargets returns random sub set of max length targets
+func randomMaxTargets(targets []fab.ProposalProcessor, max int) []fab.ProposalProcessor {
+	if len(targets) <= max {
+		return targets
+	}
+	for i := range targets {
+		j := rand.Intn(i + 1)
+		targets[i], targets[j] = targets[j], targets[i]
+	}
+	return targets[:max]
+}

pkg/fab/chconfig/chconfig_test.go

@@ -6,6 +6,7 @@ SPDX-License-Identifier: Apache-2.0
 package chconfig
 
 import (
+	reqContext "context"
 	"testing"
 
 	"time"
@@ -17,6 +18,8 @@ import (
 	"github.com/hyperledger/fabric-sdk-go/pkg/fab/mocks"
 	"github.com/hyperledger/fabric-sdk-go/pkg/fab/orderer"
 	mspmocks "github.com/hyperledger/fabric-sdk-go/pkg/msp/mocks"
+	"github.com/pkg/errors"
+
 	"github.com/stretchr/testify/assert"
 )
 
@@ -29,7 +32,7 @@ func TestChannelConfigWithPeer(t *testing.T) {
 	ctx := setupTestContext()
 	peer := getPeerWithConfigBlockPayload(t)
 
-	channelConfig, err := New(channelID, WithPeers([]fab.Peer{peer}), WithMinResponses(1))
+	channelConfig, err := New(channelID, WithPeers([]fab.Peer{peer}), WithMinResponses(1), WithMaxTargets(1))
 	if err != nil {
 		t.Fatalf("Failed to create new channel client: %s", err)
 	}
@@ -87,6 +90,40 @@ func TestChannelConfigWithOrdererError(t *testing.T) {
 
 }
 
+func TestRandomMaxTargetsSelections(t *testing.T) {
+
+	testTargets := []fab.ProposalProcessor{
+		&mockProposalProcessor{"ONE"}, &mockProposalProcessor{"TWO"}, &mockProposalProcessor{"THREE"},
+		&mockProposalProcessor{"FOUR"}, &mockProposalProcessor{"FIVE"}, &mockProposalProcessor{"SIX"},
+		&mockProposalProcessor{"SEVEN"}, &mockProposalProcessor{"EIGHT"}, &mockProposalProcessor{"NINE"},
+	}
+
+	max := 3
+	before := ""
+	for _, v := range testTargets[:max] {
+		before = before + v.(*mockProposalProcessor).name
+	}
+
+	responseTargets := randomMaxTargets(testTargets, max)
+	assert.True(t, responseTargets != nil && len(responseTargets) == max, "response target not as expected")
+
+	after := ""
+	for _, v := range responseTargets {
+		after = after + v.(*mockProposalProcessor).name
+	}
+	//make sure it is random
+	assert.False(t, before == after, "response targets are not random")
+
+	max = 0 //when zero minimum supplied, result should be empty
+	responseTargets = randomMaxTargets(testTargets, max)
+	assert.True(t, responseTargets != nil && len(responseTargets) == max, "response target not as expected")
+
+	max = 12 //greater than targets length
+	responseTargets = randomMaxTargets(testTargets, max)
+	assert.True(t, responseTargets != nil && len(responseTargets) == len(testTargets), "response target not as expected")
+
+}
+
 func setupTestContext() context.Client {
 	user := mspmocks.NewMockSigningIdentity("test", "test")
 	ctx := mocks.NewMockContext(user)
@@ -121,6 +158,15 @@ func getPeerWithConfigBlockPayload(t *testing.T) fab.Peer {
 	return peer
 }
 
+//mockProposalProcessor to mock proposal processor for random max target test
+type mockProposalProcessor struct {
+	name string
+}
+
+func (pp *mockProposalProcessor) ProcessTransactionProposal(reqCtx reqContext.Context, request fab.ProcessProposalRequest) (*fab.TransactionProposalResponse, error) {
+	return nil, errors.New("not implemented, just mock")
+}
+
 var validRootCA = `-----BEGIN CERTIFICATE-----
 MIICYjCCAgmgAwIBAgIUB3CTDOU47sUC5K4kn/Caqnh114YwCgYIKoZIzj0EAwIw
 fzELMAkGA1UEBhMCVVMxEzARBgNVBAgTCkNhbGlmb3JuaWExFjAUBgNVBAcTDVNh