Document metrics interface

Author: bilaljaved

driver/sql/metrics.go

@@ -3,9 +3,16 @@ package sql
 type (
 	// Metrics a structured metrics interface
 	Metrics interface {
+		// ReceivedNotification sends the metric to keep count of notifications received by goengine
 		ReceivedNotification(isNotification bool)
+		// QueueNotification is called when a notification is queued.
+		// It saves start time for an event on aggregate when it's queued
 		QueueNotification(notification *ProjectionNotification)
+		// StartNotificationProcessing is called when a notification processing is started
+		// It saves start time for an event on aggregate when it's picked to be processed by background processor
 		StartNotificationProcessing(notification *ProjectionNotification)
+		// FinishNotificationProcessing is called when a notification processing is finished
+		// It actually sends metrics calculating duration for which a notification spends in queue and then processed by background processor
 		FinishNotificationProcessing(notification *ProjectionNotification, success bool)
 	}
 )