[chore] [receiver/awscontainerinsight] preallocate slices (open-telem…

…etry#24962)

receiver/awscontainerinsightreceiver/internal/cadvisor/extractors/extractor.go

@@ -136,7 +136,7 @@ func assignRateValueToField(rateCalculator *awsmetrics.MetricCalculator, fields
 
 // MergeMetrics merges an array of cadvisor metrics based on common metric keys
 func MergeMetrics(metrics []*CAdvisorMetric) []*CAdvisorMetric {
-	var result []*CAdvisorMetric
+	result := make([]*CAdvisorMetric, 0, len(metrics))
 	metricMap := make(map[string]*CAdvisorMetric)
 	for _, metric := range metrics {
 		if metricKey := getMetricKey(metric); metricKey != "" {
@@ -159,7 +159,7 @@ func MergeMetrics(metrics []*CAdvisorMetric) []*CAdvisorMetric {
 // return MetricKey for merge-able metrics
 func getMetricKey(metric *CAdvisorMetric) string {
 	metricType := metric.GetMetricType()
-	metricKey := ""
+	var metricKey string
 	switch metricType {
 	case ci.TypeInstance:
 		// merge cpu, memory, net metric for type Instance

receiver/awscontainerinsightreceiver/internal/cadvisor/extractors/fs_extractor.go

@@ -24,13 +24,13 @@ func (f *FileSystemMetricExtractor) HasValue(info *cinfo.ContainerInfo) bool {
 }
 
 func (f *FileSystemMetricExtractor) GetValue(info *cinfo.ContainerInfo, _ CPUMemInfoProvider, containerType string) []*CAdvisorMetric {
-	var metrics []*CAdvisorMetric
 	if containerType == ci.TypePod || containerType == ci.TypeInfraContainer {
-		return metrics
+		return nil
 	}
 
 	containerType = getFSMetricType(containerType, f.logger)
 	stats := GetStats(info)
+	metrics := make([]*CAdvisorMetric, 0, len(stats.Filesystem))
 
 	for _, v := range stats.Filesystem {
 		metric := newCadvisorMetric(containerType, f.logger)

receiver/awscontainerinsightreceiver/internal/cadvisor/extractors/net_extractor.go

@@ -31,11 +31,10 @@ func (n *NetMetricExtractor) HasValue(info *cinfo.ContainerInfo) bool {
 }
 
 func (n *NetMetricExtractor) GetValue(info *cinfo.ContainerInfo, _ CPUMemInfoProvider, containerType string) []*CAdvisorMetric {
-	var metrics []*CAdvisorMetric
 
 	// Just a protection here, there is no Container level Net metrics
 	if containerType == ci.TypePod || containerType == ci.TypeContainer {
-		return metrics
+		return nil
 	}
 
 	// Rename type to pod so the metric name prefix is pod_
@@ -47,9 +46,10 @@ func (n *NetMetricExtractor) GetValue(info *cinfo.ContainerInfo, _ CPUMemInfoPro
 	curIfceStats := getInterfacesStats(curStats)
 
 	// used for aggregation
-	var netIfceMetrics []map[string]interface{}
+	netIfceMetrics := make([]map[string]interface{}, len(curIfceStats))
+	metrics := make([]*CAdvisorMetric, len(curIfceStats))
 
-	for _, cur := range curIfceStats {
+	for i, cur := range curIfceStats {
 		mType := getNetMetricType(containerType, n.logger)
 		netIfceMetric := make(map[string]interface{})
 
@@ -68,15 +68,15 @@ func (n *NetMetricExtractor) GetValue(info *cinfo.ContainerInfo, _ CPUMemInfoPro
 			netIfceMetric[ci.NetTotalBytes] = netIfceMetric[ci.NetRxBytes].(float64) + netIfceMetric[ci.NetTxBytes].(float64)
 		}
 
-		netIfceMetrics = append(netIfceMetrics, netIfceMetric)
+		netIfceMetrics[i] = netIfceMetric
 
 		metric := newCadvisorMetric(mType, n.logger)
 		metric.tags[ci.NetIfce] = cur.Name
 		for k, v := range netIfceMetric {
 			metric.fields[ci.MetricName(mType, k)] = v
 		}
 
-		metrics = append(metrics, metric)
+		metrics[i] = metric
 	}
 
 	aggregatedFields := ci.SumFields(netIfceMetrics)

receiver/awscontainerinsightreceiver/internal/cadvisor/testutils/helpers.go

@@ -17,13 +17,15 @@ func LoadContainerInfo(t *testing.T, file string) []*cinfo.ContainerInfo {
 	info, err := os.ReadFile(file)
 	assert.Nil(t, err, "Fail to read file content")
 
-	var result []*cinfo.ContainerInfo
 	containers := map[string]*cinfo.ContainerInfo{}
 	err = json.Unmarshal(info, &containers)
 	assert.Nil(t, err, "Fail to parse json string")
 
+	result := make([]*cinfo.ContainerInfo, len(containers))
+	i := 0
 	for _, containerInfo := range containers {
-		result = append(result, containerInfo)
+		result[i] = containerInfo
+		i++
 	}
 
 	var b bytes.Buffer