Allow marking a certain tipset as checkpointed

api/api_full.go

@@ -157,6 +157,9 @@ type FullNode interface {
 	// yet synced block headers.
 	SyncIncomingBlocks(ctx context.Context) (<-chan *types.BlockHeader, error)
 
+	// SyncCheckpoint marks a blocks as checkpointed, meaning that it won't ever fork away from it.
+	SyncCheckpoint(ctx context.Context, tsk types.TipSetKey) error
+
 	// SyncMarkBad marks a blocks as bad, meaning that it won't ever by synced.
 	// Use with extreme caution.
 	SyncMarkBad(ctx context.Context, bcid cid.Cid) error

api/apistruct/struct.go

@@ -105,6 +105,7 @@ type FullNodeStruct struct {
 		SyncState          func(context.Context) (*api.SyncState, error)                `perm:"read"`
 		SyncSubmitBlock    func(ctx context.Context, blk *types.BlockMsg) error         `perm:"write"`
 		SyncIncomingBlocks func(ctx context.Context) (<-chan *types.BlockHeader, error) `perm:"read"`
+		SyncCheckpoint     func(ctx context.Context, key types.TipSetKey) error         `perm:"admin"`
 		SyncMarkBad        func(ctx context.Context, bcid cid.Cid) error                `perm:"admin"`
 		SyncCheckBad       func(ctx context.Context, bcid cid.Cid) (string, error)      `perm:"read"`
 
@@ -704,6 +705,10 @@ func (c *FullNodeStruct) SyncIncomingBlocks(ctx context.Context) (<-chan *types.
 	return c.Internal.SyncIncomingBlocks(ctx)
 }
 
+func (c *FullNodeStruct) SyncCheckpoint(ctx context.Context, tsk types.TipSetKey) error {
+	return c.Internal.SyncCheckpoint(ctx, tsk)
+}
+
 func (c *FullNodeStruct) SyncMarkBad(ctx context.Context, bcid cid.Cid) error {
 	return c.Internal.SyncMarkBad(ctx, bcid)
 }

chain/checkpoint.go

@@ -0,0 +1,81 @@
+package chain
+
+import (
+	"encoding/json"
+
+	"github.com/filecoin-project/lotus/chain/types"
+
+	"github.com/filecoin-project/lotus/node/modules/dtypes"
+	"github.com/ipfs/go-datastore"
+	"golang.org/x/xerrors"
+)
+
+var CheckpointKey = datastore.NewKey("/chain/checks")
+
+func loadCheckpoint(ds dtypes.MetadataDS) (types.TipSetKey, error) {
+	haveChks, err := ds.Has(CheckpointKey)
+	if err != nil {
+		return types.EmptyTSK, err
+	}
+
+	if !haveChks {
+		return types.EmptyTSK, nil
+	}
+
+	tskBytes, err := ds.Get(CheckpointKey)
+	if err != nil {
+		return types.EmptyTSK, err
+	}
+
+	var tsk types.TipSetKey
+	err = json.Unmarshal(tskBytes, &tsk)
+	if err != nil {
+		return types.EmptyTSK, err
+	}
+
+	return tsk, err
+}
+
+func (syncer *Syncer) SetCheckpoint(tsk types.TipSetKey) error {
+	if tsk == types.EmptyTSK {
+		return xerrors.Errorf("called with empty tsk")
+	}
+
+	syncer.checkptLk.Lock()
+	defer syncer.checkptLk.Unlock()
+
+	ts, err := syncer.ChainStore().LoadTipSet(tsk)
+	if err != nil {
+		return xerrors.Errorf("cannot find tipset: %w", err)
+	}
+
+	hts := syncer.ChainStore().GetHeaviestTipSet()
+	anc, err := syncer.ChainStore().IsAncestorOf(ts, hts)
+	if err != nil {
+		return xerrors.Errorf("cannot determine whether checkpoint tipset is in main-chain: %w", err)
+	}
+
+	if !hts.Equals(ts) && !anc {
+		return xerrors.Errorf("cannot mark tipset as checkpoint, since it isn't in the main-chain: %w", err)
+	}
+
+	tskBytes, err := json.Marshal(tsk)
+	if err != nil {
+		return err
+	}
+
+	err = syncer.ds.Put(CheckpointKey, tskBytes)
+	if err != nil {
+		return err
+	}
+
+	syncer.checkpt = tsk
+
+	return nil
+}
+
+func (syncer *Syncer) GetCheckpoint() types.TipSetKey {
+	syncer.checkptLk.Lock()
+	defer syncer.checkptLk.Unlock()
+	return syncer.checkpt
+}

chain/sync.go

@@ -9,8 +9,11 @@ import (
 	"sort"
 	"strconv"
 	"strings"
+	"sync"
 	"time"
 
+	"github.com/filecoin-project/lotus/node/modules/dtypes"
+
 	"github.com/filecoin-project/specs-actors/actors/runtime/proof"
 
 	"github.com/Gurpartap/async"
@@ -129,10 +132,16 @@ type Syncer struct {
 	windowSize int
 
 	tickerCtxCancel context.CancelFunc
+
+	checkptLk sync.Mutex
+
+	checkpt types.TipSetKey
+
+	ds dtypes.MetadataDS
 }
 
 // NewSyncer creates a new Syncer object.
-func NewSyncer(sm *stmgr.StateManager, exchange exchange.Client, connmgr connmgr.ConnManager, self peer.ID, beacon beacon.RandomBeacon, verifier ffiwrapper.Verifier) (*Syncer, error) {
+func NewSyncer(ds dtypes.MetadataDS, sm *stmgr.StateManager, exchange exchange.Client, connmgr connmgr.ConnManager, self peer.ID, beacon beacon.RandomBeacon, verifier ffiwrapper.Verifier) (*Syncer, error) {
 	gen, err := sm.ChainStore().GetGenesis()
 	if err != nil {
 		return nil, xerrors.Errorf("getting genesis block: %w", err)
@@ -143,7 +152,14 @@ func NewSyncer(sm *stmgr.StateManager, exchange exchange.Client, connmgr connmgr
 		return nil, err
 	}
 
+	cp, err := loadCheckpoint(ds)
+	if err != nil {
+		return nil, xerrors.Errorf("error loading mpool config: %w", err)
+	}
+
 	s := &Syncer{
+		ds:             ds,
+		checkpt:        cp,
 		beacon:         beacon,
 		bad:            NewBadBlockCache(),
 		Genesis:        gent,
@@ -1361,7 +1377,7 @@ loop:
 	log.Warnf("(fork detected) synced header chain (%s - %d) does not link to our best block (%s - %d)", incoming.Cids(), incoming.Height(), known.Cids(), known.Height())
 	fork, err := syncer.syncFork(ctx, base, known)
 	if err != nil {
-		if xerrors.Is(err, ErrForkTooLong) {
+		if xerrors.Is(err, ErrForkTooLong) || xerrors.Is(err, ErrForkCheckpoint) {
 			// TODO: we're marking this block bad in the same way that we mark invalid blocks bad. Maybe distinguish?
 			log.Warn("adding forked chain to our bad tipset cache")
 			for _, b := range incoming.Blocks() {
@@ -1377,14 +1393,17 @@ loop:
 }
 
 var ErrForkTooLong = fmt.Errorf("fork longer than threshold")
+var ErrForkCheckpoint = fmt.Errorf("fork would require us to diverge from checkpointed block")
 
 // syncFork tries to obtain the chain fragment that links a fork into a common
 // ancestor in our view of the chain.
 //
-// If the fork is too long (build.ForkLengthThreshold), we add the entire subchain to the
-// denylist. Else, we find the common ancestor, and add the missing chain
+// If the fork is too long (build.ForkLengthThreshold), or would cause us to diverge from the checkpoint (ErrForkCheckpoint),
+// we add the entire subchain to the denylist. Else, we find the common ancestor, and add the missing chain
 // fragment until the fork point to the returned []TipSet.
 func (syncer *Syncer) syncFork(ctx context.Context, incoming *types.TipSet, known *types.TipSet) ([]*types.TipSet, error) {
+	// TODO: Does this mean we always ask for ForkLengthThreshold blocks from the network, even if we just need, like, 2?
+	// Would it not be better to ask in smaller chunks, given that an ~ForkLengthThreshold is very rare?
 	tips, err := syncer.Exchange.GetBlocks(ctx, incoming.Parents(), int(build.ForkLengthThreshold))
 	if err != nil {
 		return nil, err
@@ -1404,6 +1423,22 @@ func (syncer *Syncer) syncFork(ctx context.Context, incoming *types.TipSet, know
 		}
 
 		if nts.Equals(tips[cur]) {
+			// We've identified the ancestor
+			// Still need to make sure this wouldn't cause us to fork away from the checkpointed tipset
+
+			chkpt := syncer.GetCheckpoint()
+
+			if chkpt != types.EmptyTSK {
+				chkTs, err := syncer.ChainStore().LoadTipSet(chkpt)
+				if err != nil {
+					return nil, xerrors.Errorf("failed to retrieve checkpoint tipset: %w", err)
+				}
+
+				if chkTs.Height() > nts.Height() {
+					return nil, ErrForkCheckpoint
+				}
+			}
+
 			return tips[:cur+1], nil
 		}
 
@@ -1416,6 +1451,7 @@ func (syncer *Syncer) syncFork(ctx context.Context, incoming *types.TipSet, know
 			}
 		}
 	}
+
 	return nil, ErrForkTooLong
 }
 

node/impl/full/sync.go

@@ -97,6 +97,11 @@ func (a *SyncAPI) SyncIncomingBlocks(ctx context.Context) (<-chan *types.BlockHe
 	return a.Syncer.IncomingBlocks(ctx)
 }
 
+func (a *SyncAPI) SyncCheckpoint(ctx context.Context, tsk types.TipSetKey) error {
+	log.Warnf("Marking tipset %s as bad", tsk)
+	return a.Syncer.SetCheckpoint(tsk)
+}
+
 func (a *SyncAPI) SyncMarkBad(ctx context.Context, bcid cid.Cid) error {
 	log.Warnf("Marking block %s as bad", bcid)
 	a.Syncer.MarkBad(bcid)

node/modules/chain.go

@@ -163,8 +163,8 @@ func NetworkName(mctx helpers.MetricsCtx, lc fx.Lifecycle, cs *store.ChainStore,
 	return netName, err
 }
 
-func NewSyncer(lc fx.Lifecycle, sm *stmgr.StateManager, exchange exchange.Client, h host.Host, beacon beacon.RandomBeacon, verifier ffiwrapper.Verifier) (*chain.Syncer, error) {
-	syncer, err := chain.NewSyncer(sm, exchange, h.ConnManager(), h.ID(), beacon, verifier)
+func NewSyncer(lc fx.Lifecycle, ds dtypes.MetadataDS, sm *stmgr.StateManager, exchange exchange.Client, h host.Host, beacon beacon.RandomBeacon, verifier ffiwrapper.Verifier) (*chain.Syncer, error) {
+	syncer, err := chain.NewSyncer(ds, sm, exchange, h.ConnManager(), h.ID(), beacon, verifier)
 	if err != nil {
 		return nil, err
 	}