csi: Implement NodeServiceCapability_RPC_GET_VOLUME_STATS rpc call

and implement Metrics Provider for CSI driver

Signed-off-by: Humble Chirammal <hchiramm@redhat.com>

pkg/volume/csi/csi_metrics.go

@@ -0,0 +1,79 @@
+/*
+Copyright 2019 The Kubernetes 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 csi
+
+import (
+	"context"
+	"fmt"
+
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/kubernetes/pkg/volume"
+)
+
+var _ volume.MetricsProvider = &metricsCsi{}
+
+// metricsCsi represents a MetricsProvider that calculates the used,free and
+// capacity information for volume using volume path.
+
+type metricsCsi struct {
+	// the directory path the volume is mounted to.
+	targetPath string
+
+	// Volume handle or id
+	volumeID string
+
+	//csiClient with cache
+	csiClientGetter
+}
+
+// NewMetricsCsi creates a new metricsCsi with the Volume ID and path.
+func NewMetricsCsi(volumeID string, targetPath string, driverName csiDriverName) volume.MetricsProvider {
+	mc := &metricsCsi{volumeID: volumeID, targetPath: targetPath}
+	mc.csiClientGetter.driverName = driverName
+	return mc
+}
+
+func (mc *metricsCsi) GetMetrics() (*volume.Metrics, error) {
+	currentTime := metav1.Now()
+	ctx, cancel := context.WithTimeout(context.Background(), csiTimeout)
+	defer cancel()
+	// Get CSI client
+	csiClient, err := mc.csiClientGetter.Get()
+	if err != nil {
+		return nil, err
+	}
+	// Check whether "GET_VOLUME_STATS" is set
+	volumeStatsSet, err := csiClient.NodeSupportsVolumeStats(ctx)
+	if err != nil {
+		return nil, err
+	}
+	// if plugin doesnot support volume status, return.
+	if !volumeStatsSet {
+		return nil, nil
+	}
+	// Get Volumestatus
+	metrics, err := csiClient.NodeGetVolumeStats(ctx, mc.volumeID, mc.targetPath)
+	if err != nil {
+		return nil, err
+	}
+	if metrics == nil {
+		return nil, fmt.Errorf("csi.NodeGetVolumeStats returned nil metrics for volume %s", mc.volumeID)
+	}
+	//set recorded time
+	metrics.Time = currentTime
+	return metrics, nil
+}