allow configuring the lookback window

cmd/utils/flags.go

@@ -661,6 +661,11 @@ var (
 		Usage: "Default minimum difference between two consecutive block's timestamps in seconds",
 		Value: uint64(eth.DefaultConfig.Istanbul.ProposerPolicy),
 	}
+	IstanbulLookbackWindowFlag = cli.Uint64Flag{
+		Name:  "istanbul.lookbackwindow",
+		Usage: "Default number of blocks to use for forgiving downtime",
+		Value: uint64(eth.DefaultConfig.Istanbul.LookbackWindow),
+	}
 )
 
 // MakeDataDir retrieves the currently requested data directory, terminating

consensus/istanbul/config.go

@@ -29,6 +29,7 @@ type Config struct {
 	BlockPeriod          uint64         `toml:",omitempty"` // Default minimum difference between two consecutive block's timestamps in second
 	ProposerPolicy       ProposerPolicy `toml:",omitempty"` // The policy for proposer selection
 	Epoch                uint64         `toml:",omitempty"` // The number of blocks after which to checkpoint and reset the pending votes
+	LookbackWindow       uint64         `toml:",omitempty"` // The window of blocks in which a validator is forgived from voting
 	ValidatorEnodeDBPath string         `toml:",omitempty"` // The location for the validator enodes DB
 }
 
@@ -37,5 +38,6 @@ var DefaultConfig = &Config{
 	BlockPeriod:          1,
 	ProposerPolicy:       ShuffledRoundRobin,
 	Epoch:                30000,
+	LookbackWindow:       12,
 	ValidatorEnodeDBPath: "validatorenodes",
 }

eth/backend.go

@@ -246,6 +246,9 @@ func CreateConsensusEngine(ctx *node.ServiceContext, chainConfig *params.ChainCo
 		if chainConfig.Istanbul.Epoch != 0 {
 			config.Istanbul.Epoch = chainConfig.Istanbul.Epoch
 		}
+		if chainConfig.Istanbul.LookbackWindow != 0 {
+			config.Istanbul.LookbackWindow = chainConfig.Istanbul.LookbackWindow
+		}
 		config.Istanbul.ProposerPolicy = istanbul.ProposerPolicy(chainConfig.Istanbul.ProposerPolicy)
 		dataDir := getDataDirOrFail(ctx)
 		return istanbulBackend.New(&config.Istanbul, db, dataDir)

params/config.go

@@ -242,8 +242,9 @@ func (c *CliqueConfig) String() string {
 
 // IstanbulConfig is the consensus engine configs for Istanbul based sealing.
 type IstanbulConfig struct {
-	Epoch          uint64 `json:"epoch"`  // Epoch length to reset votes and checkpoint
-	ProposerPolicy uint64 `json:"policy"` // The policy for proposer selection
+	Epoch          uint64 `json:"epoch"`    // Epoch length to reset votes and checkpoint
+	ProposerPolicy uint64 `json:"policy"`   // The policy for proposer selection
+	LookbackWindow uint64 `json:"lookback"` // The number of blocks to look back when calculating uptime
 }
 
 // String implements the stringer interface, returning the consensus engine details.