e2e: add a function to reset the stats in resource monitor

The function can be called in a long-running test to clear exsiting
stats (free the memory), and start over.

test/e2e/kubelet_stats.go

@@ -25,6 +25,7 @@ import (
 	"sort"
 	"strconv"
 	"strings"
+	"sync"
 	"text/tabwriter"
 	"time"
 
@@ -346,6 +347,7 @@ func computeContainerResourceUsage(name string, oldStats, newStats *cadvisor.Con
 // list of containers, computes and cache resource usage up to
 // maxEntriesPerContainer for each container.
 type resourceCollector struct {
+	lock            sync.RWMutex
 	node            string
 	containers      []string
 	client          *client.Client
@@ -390,6 +392,8 @@ func (r *resourceCollector) collectStats(oldStats map[string]*cadvisor.Container
 		Logf("Error getting container info on %q, err: %v", r.node, err)
 		return
 	}
+	r.lock.Lock()
+	defer r.lock.Unlock()
 	for _, name := range r.containers {
 		info, ok := infos[name]
 		if !ok || len(info.Stats) < 1 {
@@ -405,6 +409,8 @@ func (r *resourceCollector) collectStats(oldStats map[string]*cadvisor.Container
 
 // LogLatest logs the latest resource usage of each container.
 func (r *resourceCollector) LogLatest() {
+	r.lock.RLock()
+	defer r.lock.RUnlock()
 	stats := make(map[string]*containerResourceUsage)
 	for _, name := range r.containers {
 		s := r.buffers[name][len(r.buffers)-1]
@@ -417,6 +423,15 @@ func (r *resourceCollector) LogLatest() {
 	Logf("\n%s", formatResourceUsageStats(r.node, stats))
 }
 
+// Reset frees the stats and start over.
+func (r *resourceCollector) Reset() {
+	r.lock.Lock()
+	defer r.lock.Unlock()
+	for _, name := range r.containers {
+		r.buffers[name] = []*containerResourceUsage{}
+	}
+}
+
 type resourceUsageByCPU []*containerResourceUsage
 
 func (r resourceUsageByCPU) Len() int           { return len(r) }
@@ -428,6 +443,8 @@ var percentiles = [...]float64{0.05, 0.50, 0.90, 0.95}
 // GetBasicCPUStats returns the 5-th, 50-th, and 95-th, percentiles the cpu
 // usage in cores for containerName. This method examines all data currently in the buffer.
 func (r *resourceCollector) GetBasicCPUStats(containerName string) map[float64]float64 {
+	r.lock.RLock()
+	defer r.lock.RUnlock()
 	result := make(map[float64]float64, len(percentiles))
 	usages := r.buffers[containerName]
 	sort.Sort(resourceUsageByCPU(usages))
@@ -476,6 +493,12 @@ func (r *resourceMonitor) Stop() {
 	}
 }
 
+func (r *resourceMonitor) Reset() {
+	for _, collector := range r.collectors {
+		collector.Reset()
+	}
+}
+
 func (r *resourceMonitor) LogLatest() {
 	for _, collector := range r.collectors {
 		collector.LogLatest()