pod-metrics: add shared folder to report metrics

At the moment, pod export their metrics using a file in a shared
directory.
To support that, virt-launcher needs to setup that directory.

Much like kubevirt is already doing, we setup the directory in tmpfs.

This patch laid the foundations; future work will enable more features
like automated cleanup.

Signed-off-by: Francesco Romani <fromani@redhat.com>

pkg/pod-metrics/metrics.go

@@ -0,0 +1,61 @@
+/*
+ * This file is part of the kubevirt project
+ *
+ * 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.
+ *
+ * Copyright 2017-2018 Red Hat, Inc.
+ *
+ */
+
+package metrics
+
+import (
+	"path/filepath"
+
+	"kubevirt.io/kubevirt/pkg/api/v1"
+	diskutils "kubevirt.io/kubevirt/pkg/ephemeral-disk-utils"
+	"kubevirt.io/kubevirt/pkg/log"
+	"kubevirt.io/kubevirt/pkg/precond"
+)
+
+func MetricsFileDirectory(baseDir string) string {
+	return filepath.Join(baseDir, "metrics-files")
+}
+
+func MetricsFileFromNamespaceName(baseDir string, namespace string, name string) string {
+	metricsFile := namespace + "_" + name
+	return filepath.Join(baseDir, "metrics-files", metricsFile)
+}
+
+func MetricsFileRemove(baseDir string, vmi *v1.VirtualMachineInstance) error {
+	namespace := precond.MustNotBeEmpty(vmi.GetObjectMeta().GetNamespace())
+	domain := precond.MustNotBeEmpty(vmi.GetObjectMeta().GetName())
+
+	file := MetricsFileFromNamespaceName(baseDir, namespace, domain)
+
+	return diskutils.RemoveFile(file)
+}
+
+func MetricsFileExists(baseDir string, vmi *v1.VirtualMachineInstance) (bool, error) {
+	namespace := precond.MustNotBeEmpty(vmi.GetObjectMeta().GetNamespace())
+	domain := precond.MustNotBeEmpty(vmi.GetObjectMeta().GetName())
+
+	filePath := MetricsFileFromNamespaceName(baseDir, namespace, domain)
+	exists, err := diskutils.FileExists(filePath)
+	if err != nil {
+		log.Log.Reason(err).Errorf("Error encountered while attempting to verify if metrics file at path %s exists.", filePath)
+
+		return false, err
+	}
+	return exists, nil
+}

pkg/virt-launcher/monitor.go

@@ -33,6 +33,7 @@ import (
 	"kubevirt.io/kubevirt/pkg/api/v1"
 	diskutils "kubevirt.io/kubevirt/pkg/ephemeral-disk-utils"
 	"kubevirt.io/kubevirt/pkg/log"
+	metrics "kubevirt.io/kubevirt/pkg/pod-metrics"
 	"kubevirt.io/kubevirt/pkg/precond"
 	cmdclient "kubevirt.io/kubevirt/pkg/virt-handler/cmd-client"
 	watchdog "kubevirt.io/kubevirt/pkg/watchdog"
@@ -155,7 +156,6 @@ func InitializeSharedDirectories(baseDir string) error {
 	if err != nil {
 		return err
 	}
-
 	err = os.MkdirAll(GracefulShutdownTriggerDir(baseDir), 0755)
 	if err != nil {
 		return err
@@ -164,6 +164,10 @@ func InitializeSharedDirectories(baseDir string) error {
 	if err != nil {
 		return err
 	}
+	err = os.MkdirAll(metrics.MetricsFileDirectory(baseDir), 0755)
+	if err != nil {
+		return err
+	}
 	return nil
 }