Add methods for listing and fetching container stats

This uses the previously unusued lib/stats.go code to return data
about container stats to the CRI API. Helpers have been built around
filtering based on the OCI API, and CPU stat reporting has been fixed.

No data on filesystem layer usage is returned at this time.

Fixes one-half of #1248

Signed-off-by: Yann Ramin <atrus@stackworks.net>

server/container_stats_list.go

@@ -1,9 +1,10 @@
 package server
 
 import (
-	"fmt"
 	"time"
 
+	"github.com/kubernetes-incubator/cri-o/lib"
+	"github.com/sirupsen/logrus"
 	"golang.org/x/net/context"
 	pb "k8s.io/kubernetes/pkg/kubelet/apis/cri/v1alpha1/runtime"
 )
@@ -15,5 +16,37 @@ func (s *Server) ListContainerStats(ctx context.Context, req *pb.ListContainerSt
 		recordOperation(operation, time.Now())
 		recordError(operation, err)
 	}()
-	return nil, fmt.Errorf("not implemented")
+
+	ctrList, err := s.ContainerServer.ListContainers()
+	if err != nil {
+		return nil, err
+	}
+	filter := req.GetFilter()
+	if filter != nil {
+		cFilter := &pb.ContainerFilter{
+			Id:            req.Filter.Id,
+			PodSandboxId:  req.Filter.PodSandboxId,
+			LabelSelector: req.Filter.LabelSelector,
+		}
+		ctrList, err = s.filterContainerList(cFilter)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	var allStats []*pb.ContainerStats
+
+	for _, container := range ctrList {
+		stats, err := s.GetContainerStats(container, &lib.ContainerStats{})
+		if err != nil {
+			logrus.Warn("unable to get stats for container %s", container.ID())
+			continue
+		}
+		response := buildContainerStats(stats, container)
+		allStats = append(allStats, response)
+	}
+
+	return &pb.ListContainerStatsResponse{
+		Stats: allStats,
+	}, nil
 }