以CollectAllPodMetricsLast()举例，看看koordinator怎样使用tsdb进行查询。

CollectAllPodMetricsLast()

• GenerateQueryParamsLast()传入metric采集间隔2倍时间
• 调用CollectAllPodMetrics()

func CollectAllPodMetricsLast(statesInformer statesinformer.StatesInformer, metricCache metriccache.MetricCache,
    metricResource metriccache.MetricResource, metricCollectInterval time.Duration) map[string]float64 {
    queryParam := GenerateQueryParamsLast(metricCollectInterval * 2)
    return CollectAllPodMetrics(statesInformer, metricCache, *queryParam, metricResource)
}

GenerateQueryParamsLast()

• end为当前时间
• start为传入offset
• 构造metriccache.QueryParam，参数aggregate为Last（最近）

func GenerateQueryParamsLast(windowDuration time.Duration) *metriccache.QueryParam {
    end := time.Now()
    start := end.Add(-windowDuration)
    queryParam := &metriccache.QueryParam{
        Aggregate: metriccache.AggregationTypeLast,
        Start:     &start,
        End:       &end,
    }
    return queryParam
}

CollectAllPodMetrics()

• 构建BuildQueryMeta
• 调用CollectPodMetric()
  • 参数：metric缓存、queryMeta、startTime、endTime。
  • 获取结果后，设置aggregate

func CollectAllPodMetrics(statesInformer statesinformer.StatesInformer, metricCache metriccache.MetricCache,
    queryParam metriccache.QueryParam, metricResource metriccache.MetricResource) map[string]float64 {
    podsMeta := statesInformer.GetAllPods()
    podsMetrics := make(map[string]float64)
    for _, podMeta := range podsMeta {
        queryMeta, err := metricResource.BuildQueryMeta(metriccache.MetricPropertiesFunc.Pod(string(podMeta.Pod.UID)))
        if err != nil {
            klog.Warningf("build pod %s/%s query meta failed, kind: %s, error: %v", podMeta.Pod.Namespace, podMeta.Pod.Name, queryMeta.GetKind(), err)
            continue
        }
        podQueryResult, err := CollectPodMetric(metricCache, queryMeta, *queryParam.Start, *queryParam.End)
        if err != nil {
            klog.Warningf("query pod %s/%s metric failed, kind: %s, error: %v", podMeta.Pod.Namespace, podMeta.Pod.Name, queryMeta.GetKind(), err)
            continue
        }
        if podQueryResult.Count() == 0 {
            klog.V(5).Infof("query pod %s/%s metric is empty, kind: %s", podMeta.Pod.Namespace, podMeta.Pod.Name, queryMeta.GetKind())
            continue
        }
        value, err := podQueryResult.Value(queryParam.Aggregate)
        if err != nil {