[FAB-10222] Honor maximum peers to send if 0

When the collection config specifies max peers, it might be 0.

Currently, gossip assumes that if the max peers is 0 then it was
omitted, and just sets the max peers to all the known peers.

Since collection membership can change in v1.2, we should be
conservative and enforce 0 max peers as 0.

Change-Id: Idef84b6d5d88a719c737aef05b65a724a3a38468
Signed-off-by: yacovm <yacovm@il.ibm.com>

gossip/gossip/gossip_impl.go

@@ -611,6 +611,9 @@ func (g *gossipServiceImpl) IdentityInfo() api.PeerIdentitySet {
 
 // SendByCriteria sends a given message to all peers that match the given SendCriteria
 func (g *gossipServiceImpl) SendByCriteria(msg *proto.SignedGossipMessage, criteria SendCriteria) error {
+	if criteria.MaxPeers == 0 {
+		return nil
+	}
 	if criteria.Timeout == 0 {
 		return errors.New("Timeout should be specified")
 	}
@@ -620,9 +623,6 @@ func (g *gossipServiceImpl) SendByCriteria(msg *proto.SignedGossipMessage, crite
 	}
 
 	membership := g.disc.GetMembership()
-	if criteria.MaxPeers == 0 {
-		criteria.MaxPeers = len(membership)
-	}
 
 	if len(criteria.Channel) > 0 {
 		gc := g.chanState.getGossipChannelByChainID(criteria.Channel)

gossip/gossip/gossip_test.go

@@ -1144,8 +1144,23 @@ func TestSendByCriteria(t *testing.T) {
 	defer stopPeers(peers)
 	msg, _ := createDataMsg(1, []byte{}, common.ChainID("A")).NoopSign()
 
+	// We send without specifying maximum peers,
+	// whic sets it to the zero value, and
+	// this is a no-op.
+	criteria := SendCriteria{
+		IsEligible: func(discovery.NetworkMember) bool {
+			t.Fatal("Shouldn't have called, because when max peers is 0, the operation is a no-op")
+			return false
+		},
+		Timeout: time.Second * 1,
+		MinAck:  1,
+	}
+	assert.NoError(t, g1.SendByCriteria(msg, criteria))
+
 	// We send without specifying a timeout
-	criteria := SendCriteria{}
+	criteria = SendCriteria{
+		MaxPeers: 100,
+	}
 	err := g1.SendByCriteria(msg, criteria)
 	assert.Error(t, err)
 	assert.Equal(t, "Timeout should be specified", err.Error())