* made monitor Mutex a RWMutex

* added Mutex protection to the numberOfElements varialbe

Signed-off-by: Jürgen Eckel <juergen@riddleandcode.com>

monitor/backend.go

@@ -25,16 +25,13 @@ func (mms *MqttMonitor) AddParticipant(address string, lastSeenTS int64) (err er
 		log.Println("[app] [Monitor] Error serializing ConversionRequest: " + err.Error())
 		return
 	}
-	increaseCounter := false
+
 	// returns an error if the entry does not exist (we have to increase the counter in this case)
 	_, err = mms.db.Get([]byte(address), nil)
 	if err != nil {
-		increaseCounter = true
+		mms.setNumDBElements(mms.getNumDBElements() + 1)
 	}
 	mms.dbMutex.Lock()
-	if increaseCounter {
-		mms.numberOfElements++
-	}
 	err = mms.db.Put([]byte(address), lastSeenBytes, nil)
 	mms.dbMutex.Unlock()
 	if err != nil {
@@ -47,9 +44,9 @@ func (mms *MqttMonitor) AddParticipant(address string, lastSeenTS int64) (err er
 }
 
 func (mms *MqttMonitor) deleteEntry(key []byte) (err error) {
+	mms.setNumDBElements(mms.getNumDBElements() - 1)
 	mms.dbMutex.Lock()
 	err = mms.db.Delete(key, nil)
-	mms.numberOfElements--
 	mms.dbMutex.Unlock()
 	return
 }

monitor/interface.go

@@ -13,7 +13,7 @@ type MQTTMonitorClientI interface {
 	Start() (err error)
 }
 
-var monitorMutex sync.Mutex
+var monitorMutex sync.RWMutex
 var mqttMonitorInstance MQTTMonitorClientI
 
 func SetMqttMonitorInstance(monitorInstance MQTTMonitorClientI) {
@@ -23,9 +23,9 @@ func SetMqttMonitorInstance(monitorInstance MQTTMonitorClientI) {
 }
 
 func LazyMqttMonitorLoader(homeDir string) {
-	monitorMutex.Lock()
+	monitorMutex.RLock()
 	tmpInstance := mqttMonitorInstance
-	monitorMutex.Unlock()
+	monitorMutex.RUnlock()
 	if tmpInstance != nil {
 		return
 	}
@@ -36,9 +36,8 @@ func LazyMqttMonitorLoader(homeDir string) {
 	if err != nil {
 		panic(err)
 	}
-	monitorMutex.Lock()
+
-	mqttMonitorInstance = NewMqttMonitorService(aciveActorsDB, *config.GetConfig())
+	SetMqttMonitorInstance(NewMqttMonitorService(aciveActorsDB, *config.GetConfig()))
-	monitorMutex.Unlock()
 	err = mqttMonitorInstance.Start()
 	if err != nil {
 		panic(err)
@@ -46,9 +45,9 @@ func LazyMqttMonitorLoader(homeDir string) {
 }
 
 func SelectPoPParticipantsOutOfActiveActors() (challenger string, challengee string, err error) {
-	monitorMutex.Lock()
+	monitorMutex.RLock()
 	challenger, challengee, err = mqttMonitorInstance.SelectPoPParticipantsOutOfActiveActors()
-	monitorMutex.Unlock()
+	monitorMutex.RUnlock()
 	return
 }
 
@@ -58,8 +57,8 @@ func Start() (err error) {
 }
 
 func AddParticipant(address string, lastSeenTS int64) (err error) {
-	monitorMutex.Lock()
+	monitorMutex.RLock()
 	err = mqttMonitorInstance.AddParticipant(address, lastSeenTS)
-	monitorMutex.Unlock()
+	monitorMutex.RUnlock()
 	return
 }

monitor/mqtt_monitor.go

@@ -24,6 +24,7 @@ type MqttMonitor struct {
 	dbMutex                     sync.Mutex // Mutex to synchronize write operations
 	CleanupPeriodicityInMinutes time.Duration
 	config                      config.Config
+	numberOfElementsMutex       sync.RWMutex
 	numberOfElements            int64
 	sdkContext                  *sdk.Context
 	contextMutex                sync.Mutex
@@ -49,6 +50,18 @@ func (mms *MqttMonitor) IsTerminated() (isTerminated bool) {
 	return
 }
 
+func (mms *MqttMonitor) getNumDBElements() int64 {
+	mms.numberOfElementsMutex.RLock()
+	defer mms.numberOfElementsMutex.RUnlock()
+	return mms.numberOfElements
+}
+
+func (mms *MqttMonitor) setNumDBElements(numElements int64) {
+	mms.numberOfElementsMutex.Lock()
+	defer mms.numberOfElementsMutex.Unlock()
+	mms.numberOfElements = numElements
+}
+
 func getClientID() string {
 	conf := config.GetConfig()
 	return "monitor-" + conf.ValidatorAddress
@@ -107,7 +120,7 @@ func (mms *MqttMonitor) Start() (err error) {
 	if err != nil {
 		return
 	}
-	mms.numberOfElements = amount
+	mms.setNumDBElements(amount)
 	go mms.runPeriodicTasks()
 	go mms.MonitorActiveParticipants()
 	go mms.CleanupDB()
@@ -116,17 +129,19 @@ func (mms *MqttMonitor) Start() (err error) {
 func (mms *MqttMonitor) getRandomNumbers() (challenger int, challengee int) {
 	for challenger == challengee {
 		// Generate random numbers
-		challenger = rand.Intn(int(mms.numberOfElements))
+		numElements := int(mms.getNumDBElements())
-		challengee = rand.Intn(int(mms.numberOfElements))
+		challenger = rand.Intn(numElements)
+		challengee = rand.Intn(numElements)
 	}
 	return
 }
 func (mms *MqttMonitor) SelectPoPParticipantsOutOfActiveActors() (challenger string, challengee string, err error) {
-	if mms.numberOfElements < 2 {
+	numElements := int(mms.getNumDBElements())
+	if numElements < 2 {
 		return
 	}
 	randomChallenger, randomChallengee := mms.getRandomNumbers()
-	log.Println("[app] [Monitor] number of elements: " + strconv.Itoa(int(mms.numberOfElements)))
+	log.Println("[app] [Monitor] number of elements: " + strconv.Itoa(numElements))
 	log.Println("[app] [Monitor] selected IDs: " + strconv.Itoa(randomChallenger) + " " + strconv.Itoa(randomChallengee))
 	iter := mms.db.NewIterator(nil, nil)
 	defer iter.Release()