Fix gas price updater & add good values

l2geth/rollup/gas_price_updater.go

@@ -7,6 +7,7 @@ type GasPriceUpdater struct {
 	gasPricer              L2GasPricer
 	epochStartBlockNumber  uint64
 	averageBlockGasLimit   uint64
+	epochLengthSeconds     uint64
 	getLatestBlockNumberFn GetLatestBlockNumberFn
 	updateL2GasPriceFn     UpdateL2GasPriceFn
 }
@@ -15,12 +16,14 @@ func NewGasPriceUpdater(
 	gasPricer *L2GasPricer,
 	epochStartBlockNumber uint64,
 	averageBlockGasLimit uint64,
+	epochLengthSeconds uint64,
 	getLatestBlockNumberFn GetLatestBlockNumberFn,
 	updateL2GasPriceFn UpdateL2GasPriceFn,
 ) *GasPriceUpdater {
 	return &GasPriceUpdater{
 		gasPricer:              *gasPricer,
 		epochStartBlockNumber:  epochStartBlockNumber,
+		epochLengthSeconds:     epochLengthSeconds,
 		averageBlockGasLimit:   averageBlockGasLimit,
 		getLatestBlockNumberFn: getLatestBlockNumberFn,
 		updateL2GasPriceFn:     updateL2GasPriceFn,
@@ -32,7 +35,8 @@ func (g *GasPriceUpdater) UpdateGasPrice() error {
 	if err != nil {
 		return err
 	}
-	averageGasPerSecond := float64((latestBlockNumber - g.epochStartBlockNumber) * g.averageBlockGasLimit)
+	averageGasPerSecond := float64((latestBlockNumber - g.epochStartBlockNumber) * g.averageBlockGasLimit / g.epochLengthSeconds)
 	g.gasPricer.CompleteEpoch(averageGasPerSecond)
+	g.epochStartBlockNumber = latestBlockNumber
 	return g.updateL2GasPriceFn(g.gasPricer.curPrice)
 }

l2geth/rollup/gas_price_updater_test.go

@@ -6,75 +6,98 @@ import (
 )
 
 type MockEpoch struct {
-	timestamp float64
 	numBlocks uint64
 }
 
 // WIP
 func TestUsageOfGasPriceUpdater(t *testing.T) {
-	startTimestamp := float64(0)
-	startGasPerSecond := float64(10)
-	endTimestamp := float64(100)
-	endGasPerSecond := float64(100)
-	mockTimestamp := float64(0) // start at timestamp 0
-	mockTimeNow := func() float64 {
-		return mockTimestamp
-	}
-	getGasTarget := GetLinearInterpolationFn(mockTimeNow, startTimestamp, endTimestamp, startGasPerSecond, endGasPerSecond)
+	gasPerSecond := 3300000.0
+	getGasTarget := func() float64 { return gasPerSecond }
+	epochLengthSeconds := 10.0
+	averageBlockGasLimit := 11000000.0
+	// Based on our 10 second epoch, we are targetting this number of blocks per second
+	numBlocksToTarget := (epochLengthSeconds * gasPerSecond) / averageBlockGasLimit
+	fmt.Println("Number of target blocks: ", numBlocksToTarget)
 
 	gasPricer := NewGasPricer(1, 1, getGasTarget, 10)
 
 	curBlock := uint64(10)
 	getLatestBlockNumber := func() (uint64, error) { return curBlock, nil }
-	updateL2GasPrice := func(x float64) error { return nil }
+	updateL2GasPrice := func(x float64) error {
+		fmt.Println("new gas price:", x)
+		return nil
+	}
 
 	// Example loop usage
 	startBlock, _ := getLatestBlockNumber()
-	gasUpdater := NewGasPriceUpdater(gasPricer, startBlock, 1, getLatestBlockNumber, updateL2GasPrice)
+	gasUpdater := NewGasPriceUpdater(gasPricer, startBlock, 11000000, 10, getLatestBlockNumber, updateL2GasPrice)
+
 	// In these mock epochs the gas price shold go up and then down again after the time has passed
 	mockEpochs := []MockEpoch{
+		// First jack up the price to show that it will grow over time
+		MockEpoch{
+			numBlocks: 10,
+		},
+		MockEpoch{
+			numBlocks: 10,
+		},
+		MockEpoch{
+			numBlocks: 10,
+		},
+		// Then stabilize around the GPS we want
+		MockEpoch{
+			numBlocks: 3,
+		},
+		MockEpoch{
+			numBlocks: 3,
+		},
+		MockEpoch{
+			numBlocks: 3,
+		},
+		MockEpoch{
+			numBlocks: 3,
+		},
+		MockEpoch{
+			numBlocks: 3,
+		},
+		MockEpoch{
+			numBlocks: 3,
+		},
+		MockEpoch{
+			numBlocks: 3,
+		},
 		MockEpoch{
-			timestamp: 0,
-			numBlocks: 5,
+			numBlocks: 3,
 		},
 		MockEpoch{
-			timestamp: 0,
-			numBlocks: 5,
+			numBlocks: 3,
 		},
+		// Then reduce the demand to show the fee goes back down to the floor
 		MockEpoch{
-			timestamp: 0,
-			numBlocks: 5,
+			numBlocks: 1,
 		},
 		MockEpoch{
-			timestamp: 0,
-			numBlocks: 5,
+			numBlocks: 1,
 		},
 		MockEpoch{
-			timestamp: 0,
-			numBlocks: 5,
+			numBlocks: 1,
 		},
 		MockEpoch{
-			timestamp: 50,
-			numBlocks: 5,
+			numBlocks: 1,
 		},
 		MockEpoch{
-			timestamp: 50,
-			numBlocks: 5,
+			numBlocks: 1,
 		},
 		MockEpoch{
-			timestamp: 50,
-			numBlocks: 5,
+			numBlocks: 1,
 		},
 		MockEpoch{
-			timestamp: 50,
-			numBlocks: 5,
+			numBlocks: 1,
 		},
 	}
 	loop := func(epoch MockEpoch) {
-		mockTimestamp = epoch.timestamp
 		curBlock += epoch.numBlocks
 		gasUpdater.UpdateGasPrice()
-		fmt.Println("gas price:", gasUpdater.gasPricer.curPrice)
 	}
 	for _, epoch := range mockEpochs {
 		loop(epoch)