consensus: dexcon: disqualify dead node (#280)

Since a qualified node might fail stopped, we need to remove them from
qualified nodes to maintain network integrity. We do this by inspect the
previous round to see if there are dead nodes. A dead node is a notary
set node that does not propose any block in the previous round. We
disqualify them by fining them so their staked value is 1 wei below
minStake. This make them unqualified for being notary set in the follow
on rounds.

1 files changed, 7 insertions, 3 deletions

diff --git a/consensus/dexcon/dexcon_test.go b/consensus/dexcon/dexcon_test.go
index f34823570..0181a80f3 100644
--- a/consensus/dexcon/dexcon_test.go
+++ b/consensus/dexcon/dexcon_test.go
@@ -31,14 +31,18 @@ import (
 	"github.com/dexon-foundation/dexon/params"
 )
 
-type GovStateFetcher struct {
+type govStateFetcher struct {
 	statedb *state.StateDB
 }
 
-func (g *GovStateFetcher) GetStateForConfigAtRound(_ uint64) *vm.GovernanceState {
+func (g *govStateFetcher) GetStateForConfigAtRound(_ uint64) *vm.GovernanceState {
 	return &vm.GovernanceState{g.statedb}
 }
 
+func (g *govStateFetcher) NotarySetNodeKeyAddresses(round uint64) (map[common.Address]struct{}, error) {
+	return make(map[common.Address]struct{}), nil
+}
+
 type DexconTestSuite struct {
 	suite.Suite
 
@@ -86,7 +90,7 @@ func (d *DexconTestSuite) SetupTest() {
 
 func (d *DexconTestSuite) TestBlockRewardCalculation() {
 	consensus := New()
-	consensus.SetGovStateFetcher(&GovStateFetcher{d.stateDB})
+	consensus.SetGovStateFetcher(&govStateFetcher{d.stateDB})
 
 	d.s.IncTotalStaked(big.NewInt(1e18))