manager.go

// (c) 2019-2020, Ava Labs, Inc. All rights reserved.
// See the file LICENSE for licensing terms.

package chains

import (
	"crypto"
	"crypto/tls"
	"errors"
	"fmt"
	"sync"
	"time"

	"github.com/ava-labs/avalanchego/api/health"
	"github.com/ava-labs/avalanchego/api/keystore"
	"github.com/ava-labs/avalanchego/api/server"
	"github.com/ava-labs/avalanchego/chains/atomic"
	"github.com/ava-labs/avalanchego/database/prefixdb"
	"github.com/ava-labs/avalanchego/ids"
	"github.com/ava-labs/avalanchego/message"
	"github.com/ava-labs/avalanchego/network"
	"github.com/ava-labs/avalanchego/snow"
	"github.com/ava-labs/avalanchego/snow/consensus/snowball"
	"github.com/ava-labs/avalanchego/snow/engine/avalanche/state"
	"github.com/ava-labs/avalanchego/snow/engine/avalanche/vertex"
	"github.com/ava-labs/avalanchego/snow/engine/common"
	"github.com/ava-labs/avalanchego/snow/engine/common/queue"
	"github.com/ava-labs/avalanchego/snow/engine/snowman/block"
	"github.com/ava-labs/avalanchego/snow/networking/router"
	"github.com/ava-labs/avalanchego/snow/networking/sender"
	"github.com/ava-labs/avalanchego/snow/networking/timeout"
	"github.com/ava-labs/avalanchego/snow/triggers"
	"github.com/ava-labs/avalanchego/snow/validators"
	"github.com/ava-labs/avalanchego/utils/constants"
	"github.com/ava-labs/avalanchego/utils/logging"
	"github.com/ava-labs/avalanchego/vms"
	"github.com/ava-labs/avalanchego/vms/metervm"
	"github.com/ava-labs/avalanchego/vms/proposervm"

	dbManager "github.com/ava-labs/avalanchego/database/manager"

	avcon "github.com/ava-labs/avalanchego/snow/consensus/avalanche"
	aveng "github.com/ava-labs/avalanchego/snow/engine/avalanche"
	avbootstrap "github.com/ava-labs/avalanchego/snow/engine/avalanche/bootstrap"

	smcon "github.com/ava-labs/avalanchego/snow/consensus/snowman"
	smeng "github.com/ava-labs/avalanchego/snow/engine/snowman"
	smbootstrap "github.com/ava-labs/avalanchego/snow/engine/snowman/bootstrap"
)

const (
	defaultChannelSize = 1
)

var (
	errUnknownChainID = errors.New("unknown chain ID")
	errUnknownVMType  = errors.New("the vm should have type avalanche.DAGVM or snowman.ChainVM")

	_ Manager = &manager{}
)

// Manager manages the chains running on this node.
// It can:
//   * Create a chain
//   * Add a registrant. When a chain is created, each registrant calls
//     RegisterChain with the new chain as the argument.
//   * Manage the aliases of chains
type Manager interface {
	ids.Aliaser

	// Return the router this Manager is using to route consensus messages to chains
	Router() router.Router

	// Create a chain in the future
	CreateChain(ChainParameters)

	// Create a chain now
	ForceCreateChain(ChainParameters)

	// Add a registrant [r]. Every time a chain is
	// created, [r].RegisterChain([new chain]) is called.
	AddRegistrant(Registrant)

	// Given an alias, return the ID of the chain associated with that alias
	Lookup(string) (ids.ID, error)

	// Given an alias, return the ID of the VM associated with that alias
	LookupVM(string) (ids.ID, error)

	// Returns the ID of the subnet that is validating the provided chain
	SubnetID(chainID ids.ID) (ids.ID, error)

	// Returns true iff the chain with the given ID exists and is finished bootstrapping
	IsBootstrapped(ids.ID) bool

	Shutdown()
}

// ChainParameters defines the chain being created
type ChainParameters struct {
	ID          ids.ID   // The ID of the chain being created
	SubnetID    ids.ID   // ID of the subnet that validates this chain
	GenesisData []byte   // The genesis data of this chain's ledger
	VMAlias     string   // The ID of the vm this chain is running
	FxAliases   []string // The IDs of the feature extensions this chain is running

	CustomBeacons validators.Set // Should only be set if the default beacons can't be used.
}

type chain struct {
	Name    string
	Engine  common.Engine
	Handler *router.Handler
	Ctx     *snow.Context
	Beacons validators.Set
}

// ChainConfig is configuration settings for the current execution.
// [Config] is the user-provided config blob for the chain.
// [Upgrade] is a chain-specific blob for coordinating upgrades.
type ChainConfig struct {
	Config  []byte
	Upgrade []byte
}

type ManagerConfig struct {
	StakingEnabled              bool            // True iff the network has staking enabled
	StakingCert                 tls.Certificate // needed to sign snowman++ blocks
	Log                         logging.Logger
	LogFactory                  logging.Factory
	VMManager                   vms.Manager // Manage mappings from vm ID --> vm
	DecisionEvents              *triggers.EventDispatcher
	ConsensusEvents             *triggers.EventDispatcher
	DBManager                   dbManager.Manager
	MsgCreator                  message.Creator  // message creator, shared with network
	Router                      router.Router    // Routes incoming messages to the appropriate chain
	Net                         network.Network  // Sends consensus messages to other validators
	ConsensusParams             avcon.Parameters // The consensus parameters (alpha, beta, etc.) for new chains
	EpochFirstTransition        time.Time
	EpochDuration               time.Duration
	Validators                  validators.Manager // Validators validating on this chain
	NodeID                      ids.ShortID        // The ID of this node
	NetworkID                   uint32             // ID of the network this node is connected to
	Server                      *server.Server     // Handles HTTP API calls
	Keystore                    keystore.Keystore
	AtomicMemory                *atomic.Memory
	AVAXAssetID                 ids.ID
	XChainID                    ids.ID
	CriticalChains              ids.Set          // Chains that can't exit gracefully
	WhitelistedSubnets          ids.Set          // Subnets to validate
	TimeoutManager              *timeout.Manager // Manages request timeouts when sending messages to other validators
	HealthService               health.Service
	RetryBootstrap              bool                    // Should Bootstrap be retried
	RetryBootstrapWarnFrequency int                     // Max number of times to retry bootstrap before warning the node operator
	SubnetConfigs               map[ids.ID]SubnetConfig // ID -> SubnetConfig
	ChainConfigs                map[string]ChainConfig  // alias -> ChainConfig
	// ShutdownNodeFunc allows the chain manager to issue a request to shutdown the node
	ShutdownNodeFunc func(exitCode int)
	MeterVMEnabled   bool // Should each VM be wrapped with a MeterVM

	AppGossipValidatorSize     int
	AppGossipNonValidatorSize  int
	GossipAcceptedFrontierSize int

	// Max Time to spend fetching a container and its
	// ancestors when responding to a GetAncestors
	BootstrapMaxTimeGetAncestors time.Duration
	// Max number of containers in a multiput message sent by this node.
	BootstrapMultiputMaxContainersSent int
	// This node will only consider the first [MultiputMaxContainersReceived]
	// containers in a multiput it receives.
	BootstrapMultiputMaxContainersReceived int

	ApricotPhase4Time            time.Time
	ApricotPhase4MinPChainHeight uint64
}

type manager struct {
	// Note: The string representation of a chain's ID is also considered to be an alias of the chain
	// That is, [chainID].String() is an alias for the chain, too
	ids.Aliaser
	ManagerConfig

	// Those notified when a chain is created
	registrants []Registrant

	unblocked     bool
	blockedChains []ChainParameters

	// Key: Subnet's ID
	// Value: Subnet description
	subnets map[ids.ID]Subnet

	chainsLock sync.Mutex
	// Key: Chain's ID
	// Value: The chain
	chains map[ids.ID]*router.Handler

	// snowman++ related interface to allow validators retrival
	validatorState validators.State
}

// New returns a new Manager
func New(config *ManagerConfig) Manager {
	return &manager{
		Aliaser:       ids.NewAliaser(),
		ManagerConfig: *config,
		subnets:       make(map[ids.ID]Subnet),
		chains:        make(map[ids.ID]*router.Handler),
	}
}

// Router that this chain manager is using to route consensus messages to chains
func (m *manager) Router() router.Router { return m.ManagerConfig.Router }

// Create a chain
func (m *manager) CreateChain(chain ChainParameters) {
	if !m.unblocked {
		m.blockedChains = append(m.blockedChains, chain)
	} else {
		m.ForceCreateChain(chain)
	}
}

// Create a chain, this is only called from the P-chain thread, except for
// creating the P-chain.
func (m *manager) ForceCreateChain(chainParams ChainParameters) {
	if m.StakingEnabled && chainParams.SubnetID != constants.PrimaryNetworkID && !m.WhitelistedSubnets.Contains(chainParams.SubnetID) {
		m.Log.Debug("Skipped creating non-whitelisted chain:\n"+
			"    ID: %s\n"+
			"    VMID:%s",
			chainParams.ID,
			chainParams.VMAlias,
		)
		return
	}
	// Assert that there isn't already a chain with an alias in [chain].Aliases
	// (Recall that the string representation of a chain's ID is also an alias
	//  for a chain)
	if alias, isRepeat := m.isChainWithAlias(chainParams.ID.String()); isRepeat {
		m.Log.Debug("there is already a chain with alias '%s'. Chain not created.",
			alias)
		return
	}
	m.Log.Info("creating chain:\n"+
		"    ID: %s\n"+
		"    VMID:%s",
		chainParams.ID,
		chainParams.VMAlias,
	)

	sb, exists := m.subnets[chainParams.SubnetID]
	if !exists {
		sb = newSubnet()
		m.subnets[chainParams.SubnetID] = sb
	}

	sb.addChain(chainParams.ID)

	chain, err := m.buildChain(chainParams, sb)
	if err != nil {
		sb.removeChain(chainParams.ID)
		if m.CriticalChains.Contains(chainParams.ID) {
			// Shut down if we fail to create a required chain (i.e. X, P or C)
			m.Log.Fatal("error creating required chain %s: %s", chainParams.ID, err)
			go m.ShutdownNodeFunc(1)
			return
		}
		m.Log.Error("error creating chain %s: %s", chainParams.ID, err)
		return
	}

	m.chainsLock.Lock()
	m.chains[chainParams.ID] = chain.Handler
	m.chainsLock.Unlock()

	// Associate the newly created chain with its default alias
	m.Log.AssertNoError(m.Alias(chainParams.ID, chainParams.ID.String()))

	// Notify those that registered to be notified when a new chain is created
	m.notifyRegistrants(chain.Name, chain.Ctx, chain.Engine)

	// Tell the chain to start processing messages.
	// If the X or P Chain panics, do not attempt to recover
	if m.CriticalChains.Contains(chainParams.ID) {
		go chain.Ctx.Log.RecoverAndPanic(chain.Handler.Dispatch)
	} else {
		go chain.Ctx.Log.RecoverAndExit(chain.Handler.Dispatch, func() {
			chain.Ctx.Log.Error("Chain with ID: %s was shutdown due to a panic", chainParams.ID)
		})
	}

	// Allows messages to be routed to the new chain
	m.ManagerConfig.Router.AddChain(chain.Handler)
}

// Create a chain
func (m *manager) buildChain(chainParams ChainParameters, sb Subnet) (*chain, error) {
	vmID, err := m.VMManager.Lookup(chainParams.VMAlias)
	if err != nil {
		return nil, fmt.Errorf("error while looking up VM: %w", err)
	}

	primaryAlias, err := m.PrimaryAlias(chainParams.ID)
	if err != nil {
		primaryAlias = chainParams.ID.String()
	}

	// Create the log and context of the chain
	chainLog, err := m.LogFactory.MakeChain(primaryAlias)
	if err != nil {
		return nil, fmt.Errorf("error while creating chain's log %w", err)
	}

	ctx := &snow.Context{
		NetworkID:            m.NetworkID,
		SubnetID:             chainParams.SubnetID,
		ChainID:              chainParams.ID,
		NodeID:               m.NodeID,
		XChainID:             m.XChainID,
		AVAXAssetID:          m.AVAXAssetID,
		Log:                  chainLog,
		DecisionDispatcher:   m.DecisionEvents,
		ConsensusDispatcher:  m.ConsensusEvents,
		Keystore:             m.Keystore.NewBlockchainKeyStore(chainParams.ID),
		SharedMemory:         m.AtomicMemory.NewSharedMemory(chainParams.ID),
		BCLookup:             m,
		SNLookup:             m,
		Namespace:            fmt.Sprintf("%s_%s_vm", constants.PlatformName, primaryAlias),
		Metrics:              m.ConsensusParams.Metrics,
		EpochFirstTransition: m.EpochFirstTransition,
		EpochDuration:        m.EpochDuration,
		ValidatorState:       m.validatorState,
		StakingCertLeaf:      m.StakingCert.Leaf,
		StakingLeafSigner:    m.StakingCert.PrivateKey.(crypto.Signer),
	}

	if sbConfigs, ok := m.SubnetConfigs[chainParams.SubnetID]; ok {
		if sbConfigs.ValidatorOnly {
			ctx.SetValidatorOnly()
		}
	}

	// Get a factory for the vm we want to use on our chain
	vmFactory, err := m.VMManager.GetFactory(vmID)
	if err != nil {
		return nil, fmt.Errorf("error while getting vmFactory: %w", err)
	}

	// Create the chain
	vm, err := vmFactory.New(ctx)
	if err != nil {
		return nil, fmt.Errorf("error while creating vm: %w", err)
	}
	// TODO: Shutdown VM if an error occurs

	fxs := make([]*common.Fx, len(chainParams.FxAliases))
	for i, fxAlias := range chainParams.FxAliases {
		fxID, err := m.VMManager.Lookup(fxAlias)
		if err != nil {
			return nil, fmt.Errorf("error while looking up Fx: %w", err)
		}

		// Get a factory for the fx we want to use on our chain
		fxFactory, err := m.VMManager.GetFactory(fxID)
		if err != nil {
			return nil, fmt.Errorf("error while getting fxFactory: %w", err)
		}

		fx, err := fxFactory.New(ctx)
		if err != nil {
			return nil, fmt.Errorf("error while creating fx: %w", err)
		}

		// Create the fx
		fxs[i] = &common.Fx{
			ID: fxID,
			Fx: fx,
		}
	}

	consensusParams := m.ConsensusParams
	if sbConfigs, ok := m.SubnetConfigs[chainParams.SubnetID]; ok && chainParams.SubnetID != constants.PrimaryNetworkID {
		consensusParams = sbConfigs.ConsensusParameters
		// TODO: move metrics to another place so this can be tidier
		consensusParams.Metrics = m.ConsensusParams.Metrics
	}
	consensusParams.Namespace = fmt.Sprintf("%s_%s", constants.PlatformName, primaryAlias)

	// The validators of this blockchain
	var vdrs validators.Set // Validators validating this blockchain
	var ok bool
	if m.StakingEnabled {
		vdrs, ok = m.Validators.GetValidators(chainParams.SubnetID)
	} else { // Staking is disabled. Every peer validates every subnet.
		vdrs, ok = m.Validators.GetValidators(constants.PrimaryNetworkID)
	}
	if !ok {
		return nil, fmt.Errorf("couldn't get validator set of subnet with ID %s. The subnet may not exist", chainParams.SubnetID)
	}

	beacons := vdrs
	if chainParams.CustomBeacons != nil {
		beacons = chainParams.CustomBeacons
	}

	bootstrapWeight := beacons.Weight()

	var chain *chain
	switch vm := vm.(type) {
	case vertex.DAGVM:
		chain, err = m.createAvalancheChain(
			ctx,
			chainParams.GenesisData,
			vdrs,
			beacons,
			vm,
			fxs,
			consensusParams,
			bootstrapWeight,
			sb,
		)
		if err != nil {
			return nil, fmt.Errorf("error while creating new avalanche vm %w", err)
		}
	case block.ChainVM:
		chain, err = m.createSnowmanChain(
			ctx,
			chainParams.GenesisData,
			vdrs,
			beacons,
			vm,
			fxs,
			consensusParams.Parameters,
			bootstrapWeight,
			sb,
		)
		if err != nil {
			return nil, fmt.Errorf("error while creating new snowman vm %w", err)
		}
	default:
		return nil, errUnknownVMType
	}

	// Register the chain with the timeout manager
	if err := m.TimeoutManager.RegisterChain(ctx, consensusParams.Namespace); err != nil {
		return nil, err
	}

	return chain, nil
}

// Implements Manager.AddRegistrant
func (m *manager) AddRegistrant(r Registrant) { m.registrants = append(m.registrants, r) }

func (m *manager) unblockChains() {
	m.unblocked = true
	blocked := m.blockedChains
	m.blockedChains = nil
	for _, chainParams := range blocked {
		m.ForceCreateChain(chainParams)
	}
}

// Create a DAG-based blockchain that uses Avalanche
func (m *manager) createAvalancheChain(
	ctx *snow.Context,
	genesisData []byte,
	vdrs,
	beacons validators.Set,
	vm vertex.DAGVM,
	fxs []*common.Fx,
	consensusParams avcon.Parameters,
	bootstrapWeight uint64,
	sb Subnet,
) (*chain, error) {
	ctx.Lock.Lock()
	defer ctx.Lock.Unlock()

	meterDBManager, err := m.DBManager.NewMeterDBManager(consensusParams.Namespace+"_db", ctx.Metrics)
	if err != nil {
		return nil, err
	}
	prefixDBManager := meterDBManager.NewPrefixDBManager(ctx.ChainID[:])
	vmDBManager := prefixDBManager.NewPrefixDBManager([]byte("vm"))

	db := prefixDBManager.Current()
	vertexDB := prefixdb.New([]byte("vertex"), db.Database)
	vertexBootstrappingDB := prefixdb.New([]byte("vertex_bs"), db.Database)
	txBootstrappingDB := prefixdb.New([]byte("tx_bs"), db.Database)

	vtxBlocker, err := queue.NewWithMissing(vertexBootstrappingDB, consensusParams.Namespace+"_vtx", ctx.Metrics)
	if err != nil {
		return nil, err
	}
	txBlocker, err := queue.New(txBootstrappingDB, consensusParams.Namespace+"_tx", ctx.Metrics)
	if err != nil {
		return nil, err
	}

	// The channel through which a VM may send messages to the consensus engine
	// VM uses this channel to notify engine that a block is ready to be made
	msgChan := make(chan common.Message, defaultChannelSize)

	// Passes messages from the consensus engine to the network
	sender := sender.Sender{}
	if err := sender.Initialize(
		ctx,
		m.MsgCreator,
		m.Net,
		m.ManagerConfig.Router,
		m.TimeoutManager,
		consensusParams.Namespace,
		consensusParams.Metrics,
		m.AppGossipValidatorSize,
		m.AppGossipNonValidatorSize,
		m.GossipAcceptedFrontierSize,
	); err != nil {
		return nil, fmt.Errorf("couldn't initialize sender: %w", err)
	}

	chainConfig, err := m.getChainConfig(ctx.ChainID)
	if err != nil {
		return nil, fmt.Errorf("error while fetching chain config: %w", err)
	}

	if m.MeterVMEnabled {
		vm = metervm.NewVertexVM(vm)
	}
	if err := vm.Initialize(
		ctx,
		vmDBManager,
		genesisData,
		chainConfig.Upgrade,
		chainConfig.Config,
		msgChan,
		fxs,
		&sender,
	); err != nil {
		return nil, fmt.Errorf("error during vm's Initialize: %w", err)
	}

	// Handles serialization/deserialization of vertices and also the
	// persistence of vertices
	vtxManager := &state.Serializer{}
	vtxManager.Initialize(ctx, vm, vertexDB)

	sampleK := consensusParams.K
	if uint64(sampleK) > bootstrapWeight {
		sampleK = int(bootstrapWeight)
	}

	// Asynchronously passes messages from the network to the consensus engine
	handler := &router.Handler{}

	timer := &router.Timer{
		Handler: handler,
		Preempt: sb.afterBootstrapped(),
	}

	// The engine handles consensus
	engine := &aveng.Transitive{}
	if err := engine.Initialize(aveng.Config{
		Config: avbootstrap.Config{
			Config: common.Config{
				Ctx:                           ctx,
				Validators:                    vdrs,
				Beacons:                       beacons,
				SampleK:                       sampleK,
				StartupAlpha:                  (3*bootstrapWeight + 3) / 4,
				Alpha:                         bootstrapWeight/2 + 1, // must be > 50%
				Sender:                        &sender,
				Subnet:                        sb,
				Timer:                         timer,
				RetryBootstrap:                m.RetryBootstrap,
				RetryBootstrapWarnFrequency:   m.RetryBootstrapWarnFrequency,
				MaxTimeGetAncestors:           m.BootstrapMaxTimeGetAncestors,
				MultiputMaxContainersSent:     m.BootstrapMultiputMaxContainersSent,
				MultiputMaxContainersReceived: m.BootstrapMultiputMaxContainersReceived,
			},
			VtxBlocked: vtxBlocker,
			TxBlocked:  txBlocker,
			Manager:    vtxManager,

			VM: vm,
		},
		Params:    consensusParams,
		Consensus: &avcon.Topological{},
	}); err != nil {
		return nil, fmt.Errorf("error initializing avalanche engine: %w", err)
	}

	// Register health check for this chain
	chainAlias, err := m.PrimaryAlias(ctx.ChainID)
	if err != nil {
		chainAlias = ctx.ChainID.String()
	}
	// Grab the context lock before calling the chain's health check
	checkFn := func() (interface{}, error) {
		ctx.Lock.Lock()
		defer ctx.Lock.Unlock()
		return engine.HealthCheck()
	}
	if err := m.HealthService.RegisterCheck(chainAlias, checkFn); err != nil {
		return nil, fmt.Errorf("couldn't add health check for chain %s: %w", chainAlias, err)
	}

	err = handler.Initialize(
		m.MsgCreator,
		engine,
		vdrs,
		msgChan,
		fmt.Sprintf("%s_handler", consensusParams.Namespace),
		consensusParams.Metrics,
	)

	return &chain{
		Name:    chainAlias,
		Engine:  engine,
		Handler: handler,
		Ctx:     ctx,
	}, err
}

// Create a linear chain using the Snowman consensus engine
func (m *manager) createSnowmanChain(
	ctx *snow.Context,
	genesisData []byte,
	vdrs,
	beacons validators.Set,
	vm block.ChainVM,
	fxs []*common.Fx,
	consensusParams snowball.Parameters,
	bootstrapWeight uint64,
	sb Subnet,
) (*chain, error) {
	ctx.Lock.Lock()
	defer ctx.Lock.Unlock()

	meterDBManager, err := m.DBManager.NewMeterDBManager(consensusParams.Namespace+"_db", ctx.Metrics)
	if err != nil {
		return nil, err
	}
	prefixDBManager := meterDBManager.NewPrefixDBManager(ctx.ChainID[:])
	vmDBManager := prefixDBManager.NewPrefixDBManager([]byte("vm"))

	db := prefixDBManager.Current()
	bootstrappingDB := prefixdb.New([]byte("bs"), db.Database)

	blocked, err := queue.NewWithMissing(bootstrappingDB, consensusParams.Namespace+"_block", ctx.Metrics)
	if err != nil {
		return nil, err
	}

	// The channel through which a VM may send messages to the consensus engine
	// VM uses this channel to notify engine that a block is ready to be made
	msgChan := make(chan common.Message, defaultChannelSize)

	// Passes messages from the consensus engine to the network
	sender := sender.Sender{}
	if err := sender.Initialize(
		ctx,
		m.MsgCreator,
		m.Net,
		m.ManagerConfig.Router,
		m.TimeoutManager,
		consensusParams.Namespace,
		consensusParams.Metrics,
		m.AppGossipValidatorSize,
		m.AppGossipNonValidatorSize,
		m.GossipAcceptedFrontierSize,
	); err != nil {
		return nil, fmt.Errorf("couldn't initialize sender: %w", err)
	}

	// first vm to be init is P-Chain once, which provides validator interface to all ProposerVMs
	if m.validatorState == nil {
		if m.ManagerConfig.StakingEnabled {
			valState, ok := vm.(validators.State)
			if !ok {
				return nil, fmt.Errorf("expected validators.State but got %T", vm)
			}

			// Initialize the validator state for future chains.
			m.validatorState = validators.NewLockedState(&ctx.Lock, valState)

			// Notice that this context is left unlocked. This is because the
			// lock will already be held when accessing these values on the
			// P-chain.
			ctx.ValidatorState = valState
		} else {
			m.validatorState = validators.NewNoState()
			ctx.ValidatorState = m.validatorState
		}
	}

	// Initialize the ProposerVM and the vm wrapped inside it
	chainConfig, err := m.getChainConfig(ctx.ChainID)
	if err != nil {
		return nil, fmt.Errorf("error while fetching chain config: %w", err)
	}

	// enable ProposerVM on this VM
	vm = proposervm.New(vm, m.ApricotPhase4Time, m.ApricotPhase4MinPChainHeight)

	if m.MeterVMEnabled {
		vm = metervm.NewBlockVM(vm)
	}
	if err := vm.Initialize(
		ctx,
		vmDBManager,
		genesisData,
		chainConfig.Upgrade,
		chainConfig.Config,
		msgChan,
		fxs,
		&sender,
	); err != nil {
		return nil, err
	}

	sampleK := consensusParams.K
	if uint64(sampleK) > bootstrapWeight {
		sampleK = int(bootstrapWeight)
	}

	// Asynchronously passes messages from the network to the consensus engine
	handler := &router.Handler{}

	timer := &router.Timer{
		Handler: handler,
		Preempt: sb.afterBootstrapped(),
	}

	// The engine handles consensus
	engine := &smeng.Transitive{}
	if err := engine.Initialize(smeng.Config{
		Config: smbootstrap.Config{
			Config: common.Config{
				Ctx:                           ctx,
				Validators:                    vdrs,
				Beacons:                       beacons,
				SampleK:                       sampleK,
				StartupAlpha:                  (3*bootstrapWeight + 3) / 4,
				Alpha:                         bootstrapWeight/2 + 1, // must be > 50%
				Sender:                        &sender,
				Subnet:                        sb,
				Timer:                         timer,
				RetryBootstrap:                m.RetryBootstrap,
				RetryBootstrapWarnFrequency:   m.RetryBootstrapWarnFrequency,
				MaxTimeGetAncestors:           m.BootstrapMaxTimeGetAncestors,
				MultiputMaxContainersSent:     m.BootstrapMultiputMaxContainersSent,
				MultiputMaxContainersReceived: m.BootstrapMultiputMaxContainersReceived,
			},
			Blocked:      blocked,
			VM:           vm,
			Bootstrapped: m.unblockChains,
		},
		Params:    consensusParams,
		Consensus: &smcon.Topological{},
	}); err != nil {
		return nil, fmt.Errorf("error initializing snowman engine: %w", err)
	}

	err = handler.Initialize(
		m.MsgCreator,
		engine,
		vdrs,
		msgChan,
		fmt.Sprintf("%s_handler", consensusParams.Namespace),
		consensusParams.Metrics,
	)
	if err != nil {
		return nil, fmt.Errorf("couldn't initialize message handler: %s", err)
	}

	// Register health checks
	chainAlias, err := m.PrimaryAlias(ctx.ChainID)
	if err != nil {
		chainAlias = ctx.ChainID.String()
	}

	checkFn := func() (interface{}, error) {
		ctx.Lock.Lock()
		defer ctx.Lock.Unlock()
		return engine.HealthCheck()
	}
	if err := m.HealthService.RegisterCheck(chainAlias, checkFn); err != nil {
		return nil, fmt.Errorf("couldn't add health check for chain %s: %w", chainAlias, err)
	}

	return &chain{
		Name:    chainAlias,
		Engine:  engine,
		Handler: handler,
		Ctx:     ctx,
	}, nil
}

func (m *manager) SubnetID(chainID ids.ID) (ids.ID, error) {
	m.chainsLock.Lock()
	defer m.chainsLock.Unlock()

	chain, exists := m.chains[chainID]
	if !exists {
		return ids.ID{}, errUnknownChainID
	}
	return chain.Context().SubnetID, nil
}

func (m *manager) IsBootstrapped(id ids.ID) bool {
	m.chainsLock.Lock()
	chain, exists := m.chains[id]
	m.chainsLock.Unlock()
	if !exists {
		return false
	}

	return chain.Engine().IsBootstrapped()
}

// Shutdown stops all the chains
func (m *manager) Shutdown() {
	m.Log.Info("shutting down chain manager")
	m.ManagerConfig.Router.Shutdown()
}

// LookupVM returns the ID of the VM associated with an alias
func (m *manager) LookupVM(alias string) (ids.ID, error) { return m.VMManager.Lookup(alias) }

// Notify registrants [those who want to know about the creation of chains]
// that the specified chain has been created
func (m *manager) notifyRegistrants(name string, ctx *snow.Context, engine common.Engine) {
	for _, registrant := range m.registrants {
		registrant.RegisterChain(name, ctx, engine)
	}
}

// Returns:
// 1) the alias that already exists, or the empty string if there is none
// 2) true iff there exists a chain such that the chain has an alias in [aliases]
func (m *manager) isChainWithAlias(aliases ...string) (string, bool) {
	for _, alias := range aliases {
		if _, err := m.Lookup(alias); err == nil {
			return alias, true
		}
	}
	return "", false
}

// getChainConfig returns value of a entry by looking at ID key and alias key
// it first searches ID key, then falls back to it's corresponding primary alias
func (m *manager) getChainConfig(id ids.ID) (ChainConfig, error) {
	if val, ok := m.ManagerConfig.ChainConfigs[id.String()]; ok {
		return val, nil
	}
	aliases, err := m.Aliases(id)
	if err != nil {
		return ChainConfig{}, err
	}
	for _, alias := range aliases {
		if val, ok := m.ManagerConfig.ChainConfigs[alias]; ok {
			return val, nil
		}
	}

	return ChainConfig{}, nil
}