Merge pull request #81 from EspressoSystems/fix/timestamps

Correct timestamps in zkevm node to avoid decreasing

synchronizer/interfaces.go

@@ -3,6 +3,7 @@ package synchronizer
 import (
 	"context"
 	"math/big"
+	"time"
 
 	"github.com/0xPolygonHermez/zkevm-node/etherman"
 	"github.com/0xPolygonHermez/zkevm-node/state"
@@ -32,6 +33,7 @@ type stateInterface interface {
 	Reset(ctx context.Context, blockNumber uint64, dbTx pgx.Tx) error
 	GetPreviousBlock(ctx context.Context, offset uint64, dbTx pgx.Tx) (*state.Block, error)
 	GetLastBatchNumber(ctx context.Context, dbTx pgx.Tx) (uint64, error)
+	GetLastBatchTime(ctx context.Context, dbTx pgx.Tx) (time.Time, error)
 	GetBatchByNumber(ctx context.Context, batchNumber uint64, dbTx pgx.Tx) (*state.Batch, error)
 	ResetTrustedState(ctx context.Context, batchNumber uint64, dbTx pgx.Tx) error
 	AddVirtualBatch(ctx context.Context, virtualBatch *state.VirtualBatch, dbTx pgx.Tx) error

synchronizer/synchronizer.go

@@ -604,6 +604,12 @@ func (s *ClientSynchronizer) processSequenceBatches(sequencedBatches []etherman.
 		log.Warn("Empty sequencedBatches array detected, ignoring...")
 		return nil
 	}
+
+	prevTimestamp, err := s.state.GetLastBatchTime(s.ctx, dbTx)
+	if err != nil {
+		log.Warn("Error fetching previous timestamp")
+		return err
+	}
 	for _, sbatch := range sequencedBatches {
 		virtualBatch := state.VirtualBatch{
 			BatchNumber:   sbatch.BatchNumber,
@@ -620,6 +626,16 @@ func (s *ClientSynchronizer) processSequenceBatches(sequencedBatches []etherman.
 			BatchL2Data:    sbatch.Transactions,
 		}
 
+		// This should not be necessary, since HotShot should enforce non-decreasing timestamps.
+		// However, since HotShot does not currently support the ValidatedState API, timestamps
+		// proposed by leaders are not checked by replicas, and may occasionally decrease. In this
+		// case, just use the previous timestamp, to avoid breaking the rest of the execution
+		// pipeline.
+		if batch.Timestamp.Before(prevTimestamp) {
+			batch.Timestamp = prevTimestamp
+		}
+		prevTimestamp = batch.Timestamp
+
 		// Forced batches no longer supported, don't need to be handled
 
 		// Now we need to check the batch. ForcedBatches should be already stored in the batch table because this is done by the sequencer
@@ -703,7 +719,7 @@ func (s *ClientSynchronizer) processSequenceBatches(sequencedBatches []etherman.
 		FromBatchNumber: sequencedBatches[0].BatchNumber,
 		ToBatchNumber:   sequencedBatches[len(sequencedBatches)-1].BatchNumber,
 	}
-	err := s.state.AddSequence(s.ctx, seq, dbTx)
+	err = s.state.AddSequence(s.ctx, seq, dbTx)
 	if err != nil {
 		log.Errorf("error adding sequence. Sequence: %+v", seq)
 		rollbackErr := dbTx.Rollback(s.ctx)