Cherry-pick #14525 to 7.x: [Metricbeat] Check length of the slice ins…

…tead of comparing with nil in cloudwatch (#14539)

* [Metricbeat] Check length of the slice instead of comparing with nil in cloudwatch (#14525)

* Check length of the slice instead of comparing with nil

(cherry picked from commit 8dce4b1)

* Update changelog

CHANGELOG.next.asciidoc

@@ -249,6 +249,7 @@ https://github.com/elastic/beats/compare/v7.0.0-alpha2...master[Check the HEAD d
 - Update azure configuration example. {issue}14224[14224]
 - Fix cloudwatch metricset with names and dimensions in config. {issue}14376[14376] {pull}14391[14391]
 - Fix marshaling of ms-since-epoch values in `elasticsearch/cluster_stats` metricset. {pull}14378[14378]
+- Fix checking tagsFilter using length in cloudwatch metricset. {pull}14525[14525]
 
 *Packetbeat*
 

x-pack/metricbeat/module/aws/cloudwatch/cloudwatch.go

@@ -450,7 +450,7 @@ func (m *MetricSet) createEvents(svcCloudwatch cloudwatchiface.ClientAPI, svcRes
 			m.Logger().Info(errors.Wrap(err, "getResourcesTags failed, skipping region "+regionName))
 		}
 
-		if tagsFilter != nil && resourceTagMap == nil {
+		if len(tagsFilter) != 0 && len(resourceTagMap) == 0 {
 			continue
 		}
 
@@ -472,7 +472,7 @@ func (m *MetricSet) createEvents(svcCloudwatch cloudwatchiface.ClientAPI, svcRes
 					labels := strings.Split(*output.Label, labelSeperator)
 					if len(labels) != 5 {
 						// if there is no tag in labels but there is a tagsFilter, then no event should be reported.
-						if tagsFilter != nil {
+						if len(tagsFilter) != 0 {
 							continue
 						}
 						eventNew := aws.InitEvent(regionName, m.AccountName, m.AccountID)
@@ -483,7 +483,7 @@ func (m *MetricSet) createEvents(svcCloudwatch cloudwatchiface.ClientAPI, svcRes
 
 					identifierValue := labels[identifierValueIdx]
 					tags := resourceTagMap[identifierValue]
-					if tagsFilter != nil && tags == nil {
+					if len(tagsFilter) != 0 && len(tags) == 0 {
 						continue
 					}