fixes after first review

observer/circularQueueNodesProvider.go

@@ -9,7 +9,7 @@ import (
 // balancing of them
 type circularQueueNodesProvider struct {
 	*baseNodeProvider
-	positionsHolder *mapCounters.MapCountersHolder
+	positionsHolder CounterMapsHolder
 }
 
 // NewCircularQueueNodesProvider returns a new instance of circularQueueNodesProvider

observer/interface.go

@@ -22,3 +22,10 @@ type NodesHolder interface {
 	Count() int
 	IsInterfaceNil() bool
 }
+
+// CounterMapsHolder defines the actions to be implemented by a component that can hold multiple counter maps
+type CounterMapsHolder interface {
+	ComputeShardPosition(availability data.ObserverDataAvailabilityType, shardID uint32, numNodes uint32) (uint32, error)
+	ComputeAllNodesPosition(availability data.ObserverDataAvailabilityType, numNodes uint32) (uint32, error)
+	IsInterfaceNil() bool
+}

observer/mapCounters/mapCountersHolder.go

@@ -12,28 +12,28 @@ var (
 	errNumNodesMustBeGreaterThanZero = errors.New("the number of nodes must be greater than 0")
 )
 
-// MapCountersHolder handles multiple counters map based on the data availability
-type MapCountersHolder struct {
+// mapCountersHolder handles multiple counters map based on the data availability
+type mapCountersHolder struct {
 	countersMap map[data.ObserverDataAvailabilityType]*mapCounter
 }
 
-// NewMapCountersHolder populates the initial map and returns a new instance of MapCountersHolder
-func NewMapCountersHolder() *MapCountersHolder {
+// NewMapCountersHolder populates the initial map and returns a new instance of mapCountersHolder
+func NewMapCountersHolder() *mapCountersHolder {
 	availabilityProvider := availabilityCommon.AvailabilityProvider{}
 	dataAvailabilityTypes := availabilityProvider.GetAllAvailabilityTypes()
 
-	countersMap := make(map[data.ObserverDataAvailabilityType]*mapCounter)
+	countersMap := make(map[data.ObserverDataAvailabilityType]*mapCounter, len(dataAvailabilityTypes))
 	for _, availability := range dataAvailabilityTypes {
 		countersMap[availability] = newMapCounter()
 	}
 
-	return &MapCountersHolder{
+	return &mapCountersHolder{
 		countersMap: countersMap,
 	}
 }
 
 // ComputeShardPosition returns the shard position based on the availability and the shard
-func (mch *MapCountersHolder) ComputeShardPosition(availability data.ObserverDataAvailabilityType, shardID uint32, numNodes uint32) (uint32, error) {
+func (mch *mapCountersHolder) ComputeShardPosition(availability data.ObserverDataAvailabilityType, shardID uint32, numNodes uint32) (uint32, error) {
 	counterMap, exists := mch.countersMap[availability]
 	if !exists {
 		return 0, errInvalidAvailability
@@ -48,7 +48,7 @@ func (mch *MapCountersHolder) ComputeShardPosition(availability data.ObserverDat
 }
 
 // ComputeAllNodesPosition returns the all nodes position based on the availability
-func (mch *MapCountersHolder) ComputeAllNodesPosition(availability data.ObserverDataAvailabilityType, numNodes uint32) (uint32, error) {
+func (mch *mapCountersHolder) ComputeAllNodesPosition(availability data.ObserverDataAvailabilityType, numNodes uint32) (uint32, error) {
 	counterMap, exists := mch.countersMap[availability]
 	if !exists {
 		return 0, errInvalidAvailability
@@ -61,3 +61,8 @@ func (mch *MapCountersHolder) ComputeAllNodesPosition(availability data.Observer
 	position := counterMap.computePositionForAllNodes(numNodes)
 	return position, nil
 }
+
+// IsInterfaceNil returns true if there is no value under the interface
+func (mch *mapCountersHolder) IsInterfaceNil() bool {
+	return mch == nil
+}

observer/mapCounters/mapCountersHolder_test.go

@@ -91,7 +91,7 @@ func TestMapCountersHolder_ComputeShardPositionShouldWorkForMultipleAvailabiliti
 
 func calculatePosAndAssertForShard(
 	t *testing.T,
-	mch *MapCountersHolder,
+	mch *mapCountersHolder,
 	availability data.ObserverDataAvailabilityType,
 	shardID uint32,
 	numNodes uint32,
@@ -102,7 +102,7 @@ func calculatePosAndAssertForShard(
 	require.Equal(t, expectedPos, pos)
 }
 
-func calculatePosAndAssert(t *testing.T, mch *MapCountersHolder, shardID uint32, numNodes uint32, expectedPos uint32) {
+func calculatePosAndAssert(t *testing.T, mch *mapCountersHolder, shardID uint32, numNodes uint32, expectedPos uint32) {
 	calculatePosAndAssertForShard(t, mch, data.AvailabilityRecent, shardID, numNodes, expectedPos)
 }
 
@@ -146,7 +146,7 @@ func TestMapCountersHolder_ComputeAllNodesPositionShouldWork(t *testing.T) {
 	calculateAllNodesPosAndAssert(t, mch, 2, 0)
 }
 
-func calculateAllNodesPosAndAssert(t *testing.T, mch *MapCountersHolder, numNodes uint32, expectedPos uint32) {
+func calculateAllNodesPosAndAssert(t *testing.T, mch *mapCountersHolder, numNodes uint32, expectedPos uint32) {
 	pos, err := mch.ComputeAllNodesPosition(data.AvailabilityRecent, numNodes)
 	require.NoError(t, err)
 	require.Equal(t, expectedPos, pos)
@@ -176,3 +176,13 @@ func TestMapCountersHolder_ConcurrentOperations(t *testing.T) {
 		}(i % 2)
 	}
 }
+
+func TestMapCountersHolder_IsInterfaceNil(t *testing.T) {
+	t.Parallel()
+
+	var mch *mapCountersHolder
+	require.True(t, mch.IsInterfaceNil())
+
+	mch = NewMapCountersHolder()
+	require.False(t, mch.IsInterfaceNil())
+}