Implement Validator Clean Up for Dynasty Transition (#329)

beacon-chain/blockchain/BUILD.bazel

@@ -31,6 +31,7 @@ go_test(
     embed = [":go_default_library"],
     deps = [
         "//beacon-chain/database:go_default_library",
+        "//beacon-chain/params:go_default_library",
         "//beacon-chain/powchain:go_default_library",
         "//beacon-chain/types:go_default_library",
         "//beacon-chain/utils:go_default_library",

beacon-chain/blockchain/core.go

@@ -74,6 +74,21 @@ func (b *BeaconChain) CrystallizedState() *types.CrystallizedState {
 	return b.state.CrystallizedState
 }
 
+// ActiveValidatorCount exposes a getter to total number of active validator.
+func (b *BeaconChain) ActiveValidatorCount() int {
+	return len(b.state.CrystallizedState.ActiveValidators)
+}
+
+// QueuedValidatorCount exposes a getter to total number of queued validator.
+func (b *BeaconChain) QueuedValidatorCount() int {
+	return len(b.state.CrystallizedState.QueuedValidators)
+}
+
+// ExitedValidatorCount exposes a getter to total number of exited validator.
+func (b *BeaconChain) ExitedValidatorCount() int {
+	return len(b.state.CrystallizedState.ExitedValidators)
+}
+
 // GenesisBlock returns the canonical, genesis block.
 func (b *BeaconChain) GenesisBlock() *types.Block {
 	return types.NewGenesisBlock()
@@ -131,6 +146,47 @@ func (b *BeaconChain) CanProcessBlock(fetcher powchain.POWBlockFetcher, block *t
 	return validTime, nil
 }
 
+// RotateValidatorSet is called  every dynasty transition. It's primary function is
+// to go through queued validators and induct them to be active, and remove bad
+// active validator whose balance is below threshold to the exit set. It also cross checks
+// every validator's switch dynasty before induct or remove.
+func (b *BeaconChain) RotateValidatorSet() ([]types.ValidatorRecord, []types.ValidatorRecord, []types.ValidatorRecord) {
+
+	var newExitedValidators = b.CrystallizedState().ExitedValidators
+	var newActiveValidators []types.ValidatorRecord
+	upperbound := b.ActiveValidatorCount()/30 + 1
+	exitCount := 0
+
+	// Loop through active validator set, remove validator whose balance is below 50% and switch dynasty > current dynasty.
+	for _, validator := range b.state.CrystallizedState.ActiveValidators {
+		if validator.Balance < params.DefaultBalance/2 {
+			newExitedValidators = append(newExitedValidators, validator)
+		} else if validator.SwitchDynasty == b.CrystallizedState().Dynasty+1 && exitCount < upperbound {
+			newExitedValidators = append(newExitedValidators, validator)
+			exitCount++
+		} else {
+			newActiveValidators = append(newActiveValidators, validator)
+		}
+	}
+	// Get the total number of validator we can induct.
+	inductNum := upperbound
+	if b.QueuedValidatorCount() < inductNum {
+		inductNum = b.QueuedValidatorCount()
+	}
+
+	// Induct queued validator to active validator set until the switch dynasty is greater than current number.
+	for i := 0; i < inductNum; i++ {
+		if b.CrystallizedState().QueuedValidators[i].SwitchDynasty > b.CrystallizedState().Dynasty+1 {
+			inductNum = i
+			break
+		}
+		newActiveValidators = append(newActiveValidators, b.CrystallizedState().QueuedValidators[i])
+	}
+	newQueuedValidators := b.CrystallizedState().QueuedValidators[inductNum:]
+
+	return newQueuedValidators, newActiveValidators, newExitedValidators
+}
+
 // persist stores the RLP encoding of the latest beacon chain state into the db.
 func (b *BeaconChain) persist() error {
 	encodedState, err := rlp.EncodeToBytes(b.state)

beacon-chain/blockchain/core_test.go

@@ -12,6 +12,7 @@ import (
 	"github.com/ethereum/go-ethereum/crypto"
 	"github.com/ethereum/go-ethereum/p2p/enr"
 	"github.com/prysmaticlabs/prysm/beacon-chain/database"
+	"github.com/prysmaticlabs/prysm/beacon-chain/params"
 	"github.com/prysmaticlabs/prysm/beacon-chain/types"
 	"github.com/prysmaticlabs/prysm/beacon-chain/utils"
 	logTest "github.com/sirupsen/logrus/hooks/test"
@@ -281,3 +282,66 @@ func TestProcessBlockWithBadHashes(t *testing.T) {
 		t.Errorf("CanProcessBlocks should have returned false")
 	}
 }
+
+func TestRotateValidatorSet(t *testing.T) {
+	config := &database.BeaconDBConfig{DataDir: "", Name: "", InMemory: true}
+	db, err := database.NewBeaconDB(config)
+	if err != nil {
+		t.Fatalf("unable to setup db: %v", err)
+	}
+	db.Start()
+	b, err := NewBeaconChain(db.DB())
+	if err != nil {
+		t.Fatalf("Unable to setup beacon chain: %v", err)
+	}
+
+	activeValidators := []types.ValidatorRecord{
+		{Balance: 10000, WithdrawalAddress: common.Address{'A'}},
+		{Balance: 15000, WithdrawalAddress: common.Address{'B'}},
+		{Balance: 20000, WithdrawalAddress: common.Address{'C'}},
+		{Balance: 25000, WithdrawalAddress: common.Address{'D'}},
+		{Balance: 30000, WithdrawalAddress: common.Address{'E'}},
+	}
+
+	queuedValidators := []types.ValidatorRecord{
+		{Balance: params.DefaultBalance, WithdrawalAddress: common.Address{'F'}},
+		{Balance: params.DefaultBalance, WithdrawalAddress: common.Address{'G'}},
+		{Balance: params.DefaultBalance, WithdrawalAddress: common.Address{'H'}},
+		{Balance: params.DefaultBalance, WithdrawalAddress: common.Address{'I'}},
+		{Balance: params.DefaultBalance, WithdrawalAddress: common.Address{'J'}},
+	}
+
+	exitedValidators := []types.ValidatorRecord{
+		{Balance: 99999, WithdrawalAddress: common.Address{'K'}},
+		{Balance: 99999, WithdrawalAddress: common.Address{'L'}},
+		{Balance: 99999, WithdrawalAddress: common.Address{'M'}},
+		{Balance: 99999, WithdrawalAddress: common.Address{'N'}},
+		{Balance: 99999, WithdrawalAddress: common.Address{'O'}},
+	}
+
+	b.CrystallizedState().ActiveValidators = activeValidators
+	b.CrystallizedState().QueuedValidators = queuedValidators
+	b.CrystallizedState().ExitedValidators = exitedValidators
+
+	if b.ActiveValidatorCount() != 5 {
+		t.Errorf("Get active validator count failed, wanted 5, got %v", b.ActiveValidatorCount())
+	}
+	if b.QueuedValidatorCount() != 5 {
+		t.Errorf("Get queued validator count failed, wanted 5, got %v", b.QueuedValidatorCount())
+	}
+	if b.ExitedValidatorCount() != 5 {
+		t.Errorf("Get exited validator count failed, wanted 5, got %v", b.ExitedValidatorCount())
+	}
+
+	newQueuedValidators, newActiveValidators, newExitedValidators := b.RotateValidatorSet()
+
+	if len(newActiveValidators) != 4 {
+		t.Errorf("Get active validator count failed, wanted 5, got %v", len(newActiveValidators))
+	}
+	if len(newQueuedValidators) != 4 {
+		t.Errorf("Get queued validator count failed, wanted 4, got %v", len(newQueuedValidators))
+	}
+	if len(newExitedValidators) != 7 {
+		t.Errorf("Get exited validator count failed, wanted 6, got %v", len(newExitedValidators))
+	}
+}