support cgroup2

* only shim v2 runc v2 ("io.containerd.runc.v2") is supported
* only PID metrics is implemented. Others should be implemented in separate PRs.
* lots of code duplication in v1 metrics and v2 metrics. Dedupe should be separate PR.

Signed-off-by: Akihiro Suda <akihiro.suda.cz@hco.ntt.co.jp>

metrics/cgroups/v2/cgroups.go

@@ -0,0 +1,95 @@
+// +build linux
+
+/*
+   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 v2
+
+import (
+	"context"
+
+	"github.com/containerd/containerd/errdefs"
+	"github.com/containerd/containerd/events"
+	"github.com/containerd/containerd/platforms"
+	"github.com/containerd/containerd/plugin"
+	"github.com/containerd/containerd/runtime"
+	"github.com/containerd/containerd/runtime/v1/linux"
+	metrics "github.com/docker/go-metrics"
+)
+
+// Config for the cgroups monitor
+type Config struct {
+	NoPrometheus bool `toml:"no_prometheus"`
+}
+
+func init() {
+	plugin.Register(&plugin.Registration{
+		Type:   plugin.TaskMonitorPlugin,
+		ID:     "cgroups-v2",
+		InitFn: New,
+		Config: &Config{},
+	})
+}
+
+// New returns a new cgroups monitor
+func New(ic *plugin.InitContext) (interface{}, error) {
+	var ns *metrics.Namespace
+	config := ic.Config.(*Config)
+	if !config.NoPrometheus {
+		ns = metrics.NewNamespace("container", "", nil)
+	}
+	collector := newCollector(ns)
+	if ns != nil {
+		metrics.Register(ns)
+	}
+	ic.Meta.Platforms = append(ic.Meta.Platforms, platforms.DefaultSpec())
+	return &cgroupsMonitor{
+		collector: collector,
+		context:   ic.Context,
+		publisher: ic.Events,
+	}, nil
+}
+
+type cgroupsMonitor struct {
+	collector *collector
+	context   context.Context
+	publisher events.Publisher
+}
+
+func (m *cgroupsMonitor) Monitor(c runtime.Task) error {
+	if err := m.collector.Add(c); err != nil {
+		return err
+	}
+	t, ok := c.(*linux.Task)
+	if !ok {
+		return nil
+	}
+	cg, err := t.Cgroup()
+	if err != nil {
+		if errdefs.IsNotFound(err) {
+			return nil
+		}
+		return err
+	}
+	// OOM handler is not implemented yet
+	_ = cg
+	return nil
+}
+
+func (m *cgroupsMonitor) Stop(c runtime.Task) error {
+	m.collector.Remove(c)
+	return nil
+}