Move metrics to core/metrics

Signed-off-by: Derek McGowan <derek@mcg.dev>

core/metrics/cgroups/v2/cgroups.go

@@ -0,0 +1,55 @@
+//go: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/v2/pkg/events"
+	"github.com/containerd/containerd/v2/runtime"
+	"github.com/docker/go-metrics"
+)
+
+// NewTaskMonitor returns a new cgroups monitor
+func NewTaskMonitor(ctx context.Context, publisher events.Publisher, ns *metrics.Namespace) (runtime.TaskMonitor, error) {
+	collector := NewCollector(ns)
+	return &cgroupsMonitor{
+		collector: collector,
+		context:   ctx,
+		publisher: publisher,
+	}, nil
+}
+
+type cgroupsMonitor struct {
+	collector *Collector
+	context   context.Context
+	publisher events.Publisher
+}
+
+func (m *cgroupsMonitor) Monitor(c runtime.Task, labels map[string]string) error {
+	if err := m.collector.Add(c, labels); err != nil {
+		return err
+	}
+	return nil
+}
+
+func (m *cgroupsMonitor) Stop(c runtime.Task) error {
+	m.collector.Remove(c)
+	return nil
+}