feat: Add metric for Store And Foward queue size

closes edgexfoundry#1138

Signed-off-by: Leonard Goodell <leonard.goodell@intel.com>

internal/constant.go

@@ -16,22 +16,21 @@
 
 package internal
 
-import (
-	"github.com/edgexfoundry/go-mod-core-contracts/v3/common"
-)
-
-const (
-	ApiTriggerRoute   = common.ApiBase + "/trigger"
-	ApiAddSecretRoute = common.ApiBase + "/secret"
-)
+import "github.com/edgexfoundry/go-mod-core-contracts/v3/common"
 
 // SDKVersion indicates the version of the SDK - will be overwritten by build
 var SDKVersion = "0.0.0"
 
 // ApplicationVersion indicates the version of the application itself, not the SDK - will be overwritten by build
 var ApplicationVersion = "0.0.0"
 
-// Names for the Common Application Service Metrics
+// Misc Constants
+const (
+	ApiTriggerRoute           = common.ApiBase + "/trigger"
+	MessageBusSubscribeTopics = "SubscribeTopics"
+)
+
+// Common Application Service Metrics constants
 const (
 	MessagesReceivedName              = "MessagesReceived"
 	InvalidMessagesReceivedName       = "InvalidMessagesReceived"
@@ -43,9 +42,8 @@ const (
 	HttpExportErrorsName              = "HttpExportErrors"
 	MqttExportSizeName                = "MqttExportSize"
 	MqttExportErrorsName              = "MqttExportErrors"
-	MessageBusSubscribeTopics         = "SubscribeTopics"
-	MessageBusPublishTopic            = "PublishTopic"
-)
+	StoreForwardQueueSizeName         = "StoreForwardQueueSize"
 
-// MetricsReservoirSize is the default Metrics Sample Reservoir size
-const MetricsReservoirSize = 1028
+	// MetricsReservoirSize is the default Metrics Sample Reservoir size
+	MetricsReservoirSize = 1028
+)

internal/runtime/storeforward.go

@@ -24,6 +24,7 @@ import (
 	"sync/atomic"
 	"time"
 
+	"github.com/edgexfoundry/app-functions-sdk-go/v3/internal"
 	"github.com/edgexfoundry/app-functions-sdk-go/v3/internal/appfunction"
 	"github.com/edgexfoundry/app-functions-sdk-go/v3/internal/bootstrap/container"
 	"github.com/edgexfoundry/app-functions-sdk-go/v3/pkg/interfaces"
@@ -48,7 +49,7 @@ type storeForwardInfo struct {
 }
 
 func newStoreAndForward(runtime *FunctionsPipelineRuntime, dic *di.Container, serviceKey string) *storeForwardInfo {
-	return &storeForwardInfo{
+	sf := &storeForwardInfo{
 		runtime:    runtime,
 		dic:        dic,
 		lc:         bootstrapContainer.LoggingClientFrom(dic.Get),
@@ -58,6 +59,22 @@ func newStoreAndForward(runtime *FunctionsPipelineRuntime, dic *di.Container, se
 		// TODO: Register counter metric when using it for the metrics capability
 		dataCount: gometrics.NewCounter(),
 	}
+
+	metricsManager := bootstrapContainer.MetricsManagerFrom(dic.Get)
+	if metricsManager == nil {
+		sf.lc.Errorf("Unable to register %s metric: MetricsManager is not available.", internal.StoreForwardQueueSizeName)
+		return sf
+	}
+
+	err := metricsManager.Register(internal.StoreForwardQueueSizeName, sf.dataCount, nil)
+	if err != nil {
+		sf.lc.Errorf("Unable to register metric %s. Collection will continue, but metric will not be reported: %v",
+			internal.StoreForwardQueueSizeName, err)
+	}
+
+	sf.lc.Infof("%s metric has been registered and will be reported (if enabled)", internal.StoreForwardQueueSizeName)
+
+	return sf
 }
 
 func (sf *storeForwardInfo) startStoreAndForwardRetryLoop(