From fb8429b0739249cdb608f4bd0dc89508a098e8d0 Mon Sep 17 00:00:00 2001
From: Martin Martinez Rivera <martinmr@dgraph.io>
Date: Thu, 4 Jun 2020 14:51:18 -0700
Subject: [PATCH 1/3] Use new field nextRaftId to give unique IDs to new nodes.

---
 dgraph/cmd/zero/zero.go | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/dgraph/cmd/zero/zero.go b/dgraph/cmd/zero/zero.go
index 0e5cd5cad60..640794147d9 100644
--- a/dgraph/cmd/zero/zero.go
+++ b/dgraph/cmd/zero/zero.go
@@ -56,6 +56,7 @@ type Server struct {
 
 	NumReplicas int
 	state       *pb.MembershipState
+	nextRaftId  uint64
 
 	nextLeaseId uint64
 	nextTxnTs   uint64
@@ -83,6 +84,7 @@ func (s *Server) Init() {
 		Groups: make(map[uint32]*pb.Group),
 		Zeros:  make(map[uint64]*pb.Member),
 	}
+	s.nextRaftId = 1
 	s.nextLeaseId = 1
 	s.nextTxnTs = 1
 	s.nextGroup = 1
@@ -217,7 +219,10 @@ func (s *Server) hasLeader(gid uint32) bool {
 func (s *Server) SetMembershipState(state *pb.MembershipState) {
 	s.Lock()
 	defer s.Unlock()
+
 	s.state = state
+	s.nextRaftId = x.Max(s.nextRaftId, s.state.MaxRaftId + 1)
+
 	if state.Zeros == nil {
 		state.Zeros = make(map[uint64]*pb.Member)
 	}
@@ -491,7 +496,8 @@ func (s *Server) Connect(ctx context.Context,
 			}
 		}
 		if m.Id == 0 {
-			m.Id = s.state.MaxRaftId + 1
+			m.Id = s.nextRaftId
+			s.nextRaftId += 1
 			proposal.MaxRaftId = m.Id
 		}
 

From b35d2455b2b5350f762669996b5e72c5aeeaee2a Mon Sep 17 00:00:00 2001
From: Martin Martinez Rivera <martinmr@dgraph.io>
Date: Thu, 4 Jun 2020 14:59:08 -0700
Subject: [PATCH 2/3] Update nextRaftId when updating the maxRaftId.

---
 dgraph/cmd/zero/raft.go | 1 +
 dgraph/cmd/zero/zero.go | 2 +-
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/dgraph/cmd/zero/raft.go b/dgraph/cmd/zero/raft.go
index 86b0aea302d..395c80189ed 100644
--- a/dgraph/cmd/zero/raft.go
+++ b/dgraph/cmd/zero/raft.go
@@ -324,6 +324,7 @@ func (n *node) applyProposal(e raftpb.Entry) (string, error) {
 			return p.Key, errInvalidProposal
 		}
 		state.MaxRaftId = p.MaxRaftId
+		n.server.nextRaftId = x.Max(n.server.nextRaftId, p.MaxRaftId+1)
 	}
 	if p.SnapshotTs != nil {
 		for gid, ts := range p.SnapshotTs {
diff --git a/dgraph/cmd/zero/zero.go b/dgraph/cmd/zero/zero.go
index 640794147d9..5ece856192c 100644
--- a/dgraph/cmd/zero/zero.go
+++ b/dgraph/cmd/zero/zero.go
@@ -221,7 +221,7 @@ func (s *Server) SetMembershipState(state *pb.MembershipState) {
 	defer s.Unlock()
 
 	s.state = state
-	s.nextRaftId = x.Max(s.nextRaftId, s.state.MaxRaftId + 1)
+	s.nextRaftId = x.Max(s.nextRaftId, s.state.MaxRaftId+1)
 
 	if state.Zeros == nil {
 		state.Zeros = make(map[uint64]*pb.Member)

From 235fbe86be08d891a46aad527a04c04783ba1823 Mon Sep 17 00:00:00 2001
From: Martin Martinez Rivera <martinmr@dgraph.io>
Date: Fri, 5 Jun 2020 11:07:15 -0700
Subject: [PATCH 3/3] Add comment.

---
 dgraph/cmd/zero/zero.go | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/dgraph/cmd/zero/zero.go b/dgraph/cmd/zero/zero.go
index 5ece856192c..d1da1cefde4 100644
--- a/dgraph/cmd/zero/zero.go
+++ b/dgraph/cmd/zero/zero.go
@@ -496,6 +496,9 @@ func (s *Server) Connect(ctx context.Context,
 			}
 		}
 		if m.Id == 0 {
+			// In certain situations, the proposal can be sent and return with an error.
+			// However,  Dgraph will keep retrying the proposal. To avoid assigning duplicating
+			// IDs, the couter is incremented every time a proposal is created.
 			m.Id = s.nextRaftId
 			s.nextRaftId += 1
 			proposal.MaxRaftId = m.Id