Implement CRI container and pods stats

See https://kep.k8s.io/2371

* Implement new CRI RPCs - `ListPodSandboxStats` and `PodSandboxStats`
  * `ListPodSandboxStats` and `PodSandboxStats` which return stats about
    pod sandbox. To obtain pod sandbox stats, underlying metrics are
    read from the pod sandbox cgroup parent.
  * Process info is obtained by calling into the underlying task
  * Network stats are taken by looking up network metrics based on the
    pod sandbox network namespace path
* Return more detailed stats for cpu and memory for existing container
  stats. These metrics use the underlying task's metrics to obtain
  stats.

Signed-off-by: David Porter <porterdavid@google.com>

pkg/cri/server/sandbox_stats_list.go

@@ -0,0 +1,80 @@
+/*
+   Copyright The containerd Authors.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+package server
+
+import (
+	sandboxstore "github.com/containerd/containerd/pkg/cri/store/sandbox"
+	"github.com/pkg/errors"
+	"golang.org/x/net/context"
+	runtime "k8s.io/cri-api/pkg/apis/runtime/v1"
+)
+
+// ListPodSandboxStats returns stats of all ready sandboxes.
+func (c *criService) ListPodSandboxStats(
+	ctx context.Context,
+	r *runtime.ListPodSandboxStatsRequest,
+) (*runtime.ListPodSandboxStatsResponse, error) {
+	sandboxes := c.sandboxesForListPodSandboxStatsRequest(r)
+
+	podSandboxStats := new(runtime.ListPodSandboxStatsResponse)
+	for _, sandbox := range sandboxes {
+		metrics, err := metricsForSandbox(sandbox)
+
+		if err != nil {
+			return nil, errors.Wrapf(err, "failed to obtain metrics for sandbox %q", sandbox.ID)
+		}
+
+		sandboxStats, err := c.podSandboxStats(ctx, sandbox, metrics)
+		if err != nil {
+			return nil, errors.Wrapf(err, "failed to decode sandbox container metrics for sandbox %q", sandbox.ID)
+		}
+		podSandboxStats.Stats = append(podSandboxStats.Stats, sandboxStats)
+	}
+
+	return podSandboxStats, nil
+}
+
+func (c *criService) sandboxesForListPodSandboxStatsRequest(r *runtime.ListPodSandboxStatsRequest) []sandboxstore.Sandbox {
+	sandboxesInStore := c.sandboxStore.List()
+
+	if r.GetFilter() == nil {
+		return sandboxesInStore
+	}
+
+	c.normalizePodSandboxStatsFilter(r.GetFilter())
+
+	var sandboxes []sandboxstore.Sandbox
+	for _, sandbox := range sandboxesInStore {
+		if r.GetFilter().GetId() != "" && sandbox.ID != r.GetFilter().GetId() {
+			continue
+		}
+
+		if r.GetFilter().GetLabelSelector() != nil &&
+			!matchLabelSelector(r.GetFilter().GetLabelSelector(), sandbox.Config.GetLabels()) {
+			continue
+		}
+
+		// We can't obtain metrics for sandboxes that aren't in ready state
+		if sandbox.Status.Get().State != sandboxstore.StateReady {
+			continue
+		}
+
+		sandboxes = append(sandboxes, sandbox)
+	}
+
+	return sandboxes
+}