routing: add option to force import MC pair history

This commit adds the `force` flag to the `XImportMissionControl` RPC
which allows skipping rules around the pair import except for what is
mandatory to make values meaningful. This can be useful for when clients
would like to forcibly override MC state in order to manipulate routing
results.

routing/missioncontrol_state.go

@@ -54,7 +54,7 @@ func (m *missionControlState) resetHistory() {
 
 // setLastPairResult stores a result for a node pair.
 func (m *missionControlState) setLastPairResult(fromNode, toNode route.Vertex,
-	timestamp time.Time, result *pairResult) {
+	timestamp time.Time, result *pairResult, force bool) {
 
 	nodePairs, ok := m.lastPairResult[fromNode]
 	if !ok {
@@ -74,7 +74,7 @@ func (m *missionControlState) setLastPairResult(fromNode, toNode route.Vertex,
 		// prevents the success range from shrinking when there is no
 		// reason to do so. For example: small amount probes shouldn't
 		// affect a previous success for a much larger amount.
-		if successAmt > current.SuccessAmt {
+		if force || successAmt > current.SuccessAmt {
 			current.SuccessAmt = successAmt
 		}
 
@@ -83,7 +83,9 @@ func (m *missionControlState) setLastPairResult(fromNode, toNode route.Vertex,
 		// are likely to succeed. We don't want to clear the failure
 		// completely, because we haven't learnt much for amounts above
 		// the current success amount.
-		if !current.FailTime.IsZero() && successAmt >= current.FailAmt {
+		if force || (!current.FailTime.IsZero() &&
+			successAmt >= current.FailAmt) {
+
 			current.FailAmt = successAmt + 1
 		}
 	} else {
@@ -100,7 +102,7 @@ func (m *missionControlState) setLastPairResult(fromNode, toNode route.Vertex,
 		// come in out of order. This check makes it easier for payment
 		// processes to converge to a final state.
 		failInterval := timestamp.Sub(current.FailTime)
-		if failAmt > current.FailAmt &&
+		if !force && failAmt > current.FailAmt &&
 			failInterval < m.minFailureRelaxInterval {
 
 			log.Debugf("Ignoring higher amount failure within min "+
@@ -213,7 +215,9 @@ func (m *missionControlState) getSnapshot() *MissionControlSnapshot {
 // importSnapshot takes an existing snapshot and merges it with our current
 // state if the result provided are fresher than our current results. It returns
 // the number of pairs that were used.
-func (m *missionControlState) importSnapshot(snapshot *MissionControlSnapshot) int {
+func (m *missionControlState) importSnapshot(snapshot *MissionControlSnapshot,
+	force bool) int {
+
 	var imported int
 
 	for _, pair := range snapshot.Pairs {
@@ -230,13 +234,13 @@ func (m *missionControlState) importSnapshot(snapshot *MissionControlSnapshot) i
 		failResult := failPairResult(pair.FailAmt)
 		imported += m.importResult(
 			lastResult.FailTime, pair.FailTime, failResult,
-			fromNode, toNode,
+			fromNode, toNode, force,
 		)
 
 		successResult := successPairResult(pair.SuccessAmt)
 		imported += m.importResult(
 			lastResult.SuccessTime, pair.SuccessTime, successResult,
-			fromNode, toNode,
+			fromNode, toNode, force,
 		)
 	}
 
@@ -244,9 +248,10 @@ func (m *missionControlState) importSnapshot(snapshot *MissionControlSnapshot) i
 }
 
 func (m *missionControlState) importResult(currentTs, importedTs time.Time,
-	importedResult pairResult, fromNode, toNode route.Vertex) int {
+	importedResult pairResult, fromNode, toNode route.Vertex,
+	force bool) int {
 
-	if currentTs.After(importedTs) {
+	if !force && currentTs.After(importedTs) {
 		log.Debugf("Not setting pair result for %v->%v (%v) "+
 			"success=%v, timestamp %v older than last result %v",
 			fromNode, toNode, importedResult.amt,
@@ -255,7 +260,9 @@ func (m *missionControlState) importResult(currentTs, importedTs time.Time,
 		return 0
 	}
 
-	m.setLastPairResult(fromNode, toNode, importedTs, &importedResult)
+	m.setLastPairResult(
+		fromNode, toNode, importedTs, &importedResult, force,
+	)
 
 	return 1
 }