Fix nil pointer exception on restart after removing a peer.

Author: Pawan Rawal

conn/node.go

@@ -340,7 +340,7 @@ func (n *Node) doSendMessage(pool *Pool, data []byte) {
 	go func() {
 		_, err := c.RaftMessage(ctx, p)
 		if err != nil {
-			x.Printf("Error while sending message to node with addr: %d, err: %v\n", pool.Addr, err)
+			x.Printf("Error while sending message to node with addr: %s, err: %v\n", pool.Addr, err)
 		}
 		ch <- err
 	}()

dgraph/cmd/zero/run.go

@@ -198,6 +198,7 @@ func (st *state) removeNode(w http.ResponseWriter, r *http.Request) {
 		x.SetStatus(w, x.Error, err.Error())
 		return
 	}
+	w.Write([]byte(fmt.Sprintf("Removed node with group: %v, idx: %v", groupId, nodeId)))
 	return
 }
 

worker/groups.go

@@ -241,12 +241,16 @@ func (g *groupi) applyState(state *intern.MembershipState) {
 			go conn.Get().Connect(member.Addr)
 		}
 	}
-	for _, member := range g.state.Removed {
-		if member.GroupId == g.Node.gid && g.Node.AmLeader() {
-			go g.Node.ProposePeerRemoval(context.Background(), member.Id)
+
+	// While restarting we fill Node information after retrieving initial state.
+	if g.Node != nil {
+		for _, member := range g.state.Removed {
+			if member.GroupId == g.Node.gid && g.Node.AmLeader() {
+				go g.Node.ProposePeerRemoval(context.Background(), member.Id)
+			}
+			// Each node should have different id and address.
+			conn.Get().Remove(member.Addr)
 		}
-		// Each node should have different id and address.
-		conn.Get().Remove(member.Addr)
 	}
 }