Add gas processing speed to logging (#10)

* Add time taken and gas rate to log

* Update backend_impl.go

backend/backend_impl.go

@@ -12,6 +12,7 @@ package backend
 
 import (
 	"context"
+	"time"
 
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/core"
@@ -41,6 +42,11 @@ type BackendImpl struct {
 
 	chainHeadFeed event.Feed
 	scope         event.SubscriptionScope
+
+	// Perf related stat
+	blkSinceLastReport uint64
+	gasProcessed       uint64
+	timeTaken          time.Duration
 }
 
 // NewBackendImpl creates a new backend.
@@ -79,6 +85,7 @@ func (b *BackendImpl) StateArchive() worldstate.LayeredWorldStateArchive {
 
 // ImportBlock process and import a block.
 func (b *BackendImpl) ImportBlock(ctx context.Context, blk *types.Block, prvBlk *types.Block) error {
+	start := time.Now()
 	// Check if this block has already been imported
 	exists, err := b.bc.HasBlock(ctx, blk.Hash())
 	if err != nil {
@@ -123,7 +130,19 @@ func (b *BackendImpl) ImportBlock(ctx context.Context, blk *types.Block, prvBlk
 	if err != nil {
 		log.Warnf("Fail to set head to %v: %v", blk.Hash(), err.Error())
 	}
-	log.Infof("Successfully processed block %v (%v): txn %v gas used %v", blk.NumberU64(), blk.Hash(), len(receipts), gasUsed)
+	timeTaken := time.Since(start)
+	log.Infof("Successfully processed block %v (%v): txn %v gas used %v, time taken %v", blk.NumberU64(), blk.Hash(), len(receipts), gasUsed, timeTaken)
+	// Report gas rate per 10 blocks
+	b.gasProcessed += gasUsed
+	b.timeTaken = b.timeTaken + timeTaken
+	b.blkSinceLastReport++
+	if b.blkSinceLastReport >= 10 {
+		gasRate := float64(b.gasProcessed) / 1e6 / b.timeTaken.Seconds()
+		log.Infof("Current gas processing speed is %.2f M/s", gasRate)
+		b.gasProcessed = 0
+		b.timeTaken = 0
+		b.blkSinceLastReport = 0
+	}
 	// Send event
 	b.chainHeadFeed.Send(core.ChainHeadEvent{Block: blk})
 	return nil