Disable view change optionally

-disable_view_change flag controls the behavior.  Default is enable view
change.

cmd/harmony/main.go

@@ -113,6 +113,10 @@ var (
 
 	// dbDir is the database directory.
 	dbDir = flag.String("db_dir", "", "blockchain database directory")
+
+	// Disable view change.
+	disableViewChange = flag.Bool("disable_view_change", false,
+		"Do not propose view change (testing only)")
 )
 
 func initSetup() {
@@ -267,6 +271,9 @@ func setUpConsensusAndNode(nodeConfig *nodeconfig.ConfigType) *node.Node {
 		os.Exit(1)
 	}
 	currentConsensus.MinPeers = *minPeers
+	if *disableViewChange {
+		currentConsensus.DisableViewChangeForTestingOnly()
+	}
 
 	// Current node.
 	chainDBFactory := &shardchain.LDBFactory{RootDir: nodeConfig.DBDir}

consensus/consensus.go

@@ -149,6 +149,9 @@ type Consensus struct {
 
 	// Used to convey to the consensus main loop that block syncing has finished.
 	syncReadyChan chan struct{}
+
+	// If true, this consensus will not propose view change.
+	disableViewChange bool
 }
 
 // StakeInfoFinder returns the stake information finder instance this
@@ -163,6 +166,16 @@ func (consensus *Consensus) SetStakeInfoFinder(stakeInfoFinder StakeInfoFinder)
 	consensus.stakeInfoFinder = stakeInfoFinder
 }
 
+// DisableViewChangeForTestingOnly makes the receiver not propose view
+// changes when it should, e.g. leader timeout.
+//
+// As the name implies, this is intended for testing only,
+// and should not be used on production network.
+// This is also not part of the long-term consensus API and may go away later.
+func (consensus *Consensus) DisableViewChangeForTestingOnly() {
+	consensus.disableViewChange = true
+}
+
 // BlocksSynchronized lets the main loop know that block synchronization finished
 // thus the blockchain is likely to be up to date.
 func (consensus *Consensus) BlocksSynchronized() {

consensus/view_change.go

@@ -138,6 +138,9 @@ func createTimeout() map[string]*utils.Timeout {
 
 // startViewChange send a  new view change
 func (consensus *Consensus) startViewChange(viewID uint32) {
+	if consensus.disableViewChange {
+		return
+	}
 	for k := range consensus.consensusTimeout {
 		if k != "viewchange" {
 			consensus.consensusTimeout[k].Stop()