From eccdddbff92c1588e628f874d73ae557351c76f7 Mon Sep 17 00:00:00 2001
From: Jimmy Hu <jimmy.hu@dexon.org>
Date: Wed, 31 Oct 2018 12:51:54 +0800
Subject: core: Add a repeat vote state. (#280)

---
 core/agreement-state.go      | 44 ++++++++++++++++++++++++++++++++++++--------
 core/agreement-state_test.go | 30 ++++++++++++++++++++++++++----
 core/agreement_test.go       | 43 +++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 105 insertions(+), 12 deletions(-)

diff --git a/core/agreement-state.go b/core/agreement-state.go
index 56c6c27..77195ac 100644
--- a/core/agreement-state.go
+++ b/core/agreement-state.go
@@ -19,7 +19,6 @@ package core
 
 import (
 	"fmt"
-	"math"
 
 	"github.com/dexon-foundation/dexon-consensus-core/common"
 	"github.com/dexon-foundation/dexon-consensus-core/core/types"
@@ -40,6 +39,7 @@ const (
 	statePreCommit
 	stateCommit
 	stateForward
+	stateRepeatVote
 )
 
 var nullBlockHash = common.Hash{}
@@ -127,26 +127,54 @@ func (s *commitState) nextState() (agreementState, error) {
 	} else {
 		hash = skipBlockHash
 	}
-	s.a.recv.ProposeVote(&types.Vote{
+	vote := &types.Vote{
 		Type:      types.VoteCom,
 		BlockHash: hash,
 		Period:    s.a.period,
-	})
-	return newForwardState(s.a), nil
+	}
+	s.a.recv.ProposeVote(vote)
+	return newForwardState(s.a, vote), nil
 }
 
 // ----- ForwardState -----
 type forwardState struct {
-	a *agreementData
+	a    *agreementData
+	vote *types.Vote
 }
 
-func newForwardState(a *agreementData) *forwardState {
-	return &forwardState{a: a}
+func newForwardState(a *agreementData, vote *types.Vote) *forwardState {
+	return &forwardState{
+		a:    a,
+		vote: vote,
+	}
 }
 
 func (s *forwardState) state() agreementStateType { return stateForward }
-func (s *forwardState) clocks() int               { return math.MaxInt32 }
+func (s *forwardState) clocks() int               { return 4 }
 
 func (s *forwardState) nextState() (agreementState, error) {
+	return newRepeatVoteState(s.a, s.vote), nil
+}
+
+// ----- RepeatVoteState -----
+// repeateVoteState is a special state to ensure the assumption in the consensus
+// algorithm that every vote will eventually arrive for all nodes.
+type repeatVoteState struct {
+	a    *agreementData
+	vote *types.Vote
+}
+
+func newRepeatVoteState(a *agreementData, vote *types.Vote) *repeatVoteState {
+	return &repeatVoteState{
+		a:    a,
+		vote: vote,
+	}
+}
+
+func (s *repeatVoteState) state() agreementStateType { return stateRepeatVote }
+func (s *repeatVoteState) clocks() int               { return 4 }
+
+func (s *repeatVoteState) nextState() (agreementState, error) {
+	s.a.recv.ProposeVote(s.vote)
 	return s, nil
 }
diff --git a/core/agreement-state_test.go b/core/agreement-state_test.go
index 429e124..862ac3e 100644
--- a/core/agreement-state_test.go
+++ b/core/agreement-state_test.go
@@ -233,14 +233,36 @@ func (s *AgreementStateTestSuite) TestCommitState() {
 
 func (s *AgreementStateTestSuite) TestForwardState() {
 	a := s.newAgreement(4)
-	state := newForwardState(a.data)
+	vote := &types.Vote{
+		BlockHash: common.NewRandomHash(),
+	}
+	state := newForwardState(a.data, vote)
 	s.Equal(stateForward, state.state())
-	s.True(state.clocks() > 100000)
+	s.Equal(4, state.clocks())
 
-	// nextState() should return instantly without doing anything.
-	_, err := state.nextState()
+	newState, err := state.nextState()
 	s.Require().Nil(err)
 	s.Require().Len(s.voteChan, 0)
+	s.Equal(stateRepeatVote, newState.state())
+}
+
+func (s *AgreementStateTestSuite) TestRepeatVoteState() {
+	a := s.newAgreement(4)
+	vote := &types.Vote{
+		BlockHash: common.NewRandomHash(),
+	}
+	state := newRepeatVoteState(a.data, vote)
+	s.Equal(stateRepeatVote, state.state())
+	s.Equal(4, state.clocks())
+
+	for i := 0; i < 5; i++ {
+		newState, err := state.nextState()
+		s.Require().Nil(err)
+		s.Require().Len(s.voteChan, 1)
+		proposedVote := <-s.voteChan
+		s.Equal(vote, proposedVote)
+		s.Equal(stateRepeatVote, newState.state())
+	}
 }
 
 func TestAgreementState(t *testing.T) {
diff --git a/core/agreement_test.go b/core/agreement_test.go
index e4e05cd..0e3814e 100644
--- a/core/agreement_test.go
+++ b/core/agreement_test.go
@@ -183,6 +183,49 @@ func (s *AgreementTestSuite) TestSimpleConfirm() {
 	s.Equal(blockHash, confirmBlock)
 }
 
+func (s *AgreementTestSuite) TestPartitionOnCommitVote() {
+	a := s.newAgreement(4)
+	// InitialState
+	a.nextState()
+	// PreCommitState
+	s.Require().Len(s.blockChan, 1)
+	blockHash := <-s.blockChan
+	block, exist := s.block[blockHash]
+	s.Require().True(exist)
+	s.Require().NoError(a.processBlock(block))
+	s.Require().Len(s.voteChan, 1)
+	vote := <-s.voteChan
+	s.Equal(types.VoteInit, vote.Type)
+	s.Equal(blockHash, vote.BlockHash)
+	a.nextState()
+	// CommitState
+	s.Require().Len(s.voteChan, 1)
+	vote = <-s.voteChan
+	s.Equal(types.VotePreCom, vote.Type)
+	s.Equal(blockHash, vote.BlockHash)
+	for nID := range s.auths {
+		v := s.copyVote(vote, nID)
+		s.Require().NoError(a.processVote(v))
+	}
+	a.nextState()
+	// ForwardState
+	s.Require().Len(s.voteChan, 1)
+	vote = <-s.voteChan
+	s.Equal(types.VoteCom, vote.Type)
+	s.Equal(blockHash, vote.BlockHash)
+	s.Equal(blockHash, a.data.lockValue)
+	s.Equal(uint64(1), a.data.lockRound)
+	// RepeateVoteState
+	a.nextState()
+	// The agreement does not receive others commit vote, it will keep re-sending.
+	for i := 0; i < 5; i++ {
+		a.nextState()
+		s.Require().Len(s.voteChan, 1)
+		proposedVote := <-s.voteChan
+		s.Equal(vote, proposedVote)
+	}
+}
+
 func (s *AgreementTestSuite) TestFastForwardCond1() {
 	votes := 0
 	a := s.newAgreement(4)
-- 
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