Move gc/scheduler to plugins/gc

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

plugins/gc/metrics.go

@@ -0,0 +1,34 @@
+/*
+   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 scheduler
+
+import "github.com/docker/go-metrics"
+
+var (
+	// collectionCounter metrics for counter of gc scheduler collections.
+	collectionCounter metrics.LabeledCounter
+
+	// gcTimeHist histogram metrics for duration of gc scheduler collections.
+	gcTimeHist metrics.Timer
+)
+
+func init() {
+	ns := metrics.NewNamespace("containerd", "gc", nil)
+	collectionCounter = ns.NewLabeledCounter("collections", "counter of gc scheduler collections", "status")
+	gcTimeHist = ns.NewTimer("gc", "duration of gc scheduler collections")
+	metrics.Register(ns)
+}