feat(zfspv): adding backup and restore support (#162)

This commit adds support for Backup and Restore controller, which will be watching for
the events. The velero plugin will create a Backup CR to create a backup
with the remote location information, the controller will send the data
to that remote location.

In the same way, the velero plugin will create a Restore CR to restore the
volume from the the remote location and the restore controller will restore
the data.

Steps to use velero plugin for ZFS-LocalPV are :

1. install velero

2. add openebs plugin

velero plugin add openebs/velero-plugin:latest

3. Create the volumesnapshot location :

for full backup :-

```yaml
apiVersion: velero.io/v1
kind: VolumeSnapshotLocation
metadata:
  name: default
  namespace: velero
spec:
  provider: openebs.io/zfspv-blockstore
  config:
    bucket: velero
    prefix: zfs
    namespace: openebs
    provider: aws
    region: minio
    s3ForcePathStyle: "true"
    s3Url: http://minio.velero.svc:9000
```

for incremental backup :-

```yaml
apiVersion: velero.io/v1
kind: VolumeSnapshotLocation
metadata:
  name: default
  namespace: velero
spec:
  provider: openebs.io/zfspv-blockstore
  config:
    bucket: velero
    prefix: zfs
    backup: incremental
    namespace: openebs
    provider: aws
    region: minio
    s3ForcePathStyle: "true"
    s3Url: http://minio.velero.svc:9000
```

4. Create backup

velero backup create my-backup --snapshot-volumes --include-namespaces=velero-ns --volume-snapshot-locations=aws-cloud-default --storage-location=default

5. Create Schedule

velero create schedule newschedule  --schedule="*/1 * * * *" --snapshot-volumes --include-namespaces=velero-ns --volume-snapshot-locations=aws-local-default --storage-location=default

6. Restore from backup

velero restore create --from-backup my-backup --restore-volumes=true --namespace-mappings velero-ns:ns1



Signed-off-by: Pawan <pawan@mayadata.io>

pkg/mgmt/restore/start.go

@@ -0,0 +1,107 @@
+/*
+Copyright 2020 The OpenEBS 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 restore
+
+import (
+	"sync"
+
+	"github.com/pkg/errors"
+	"k8s.io/klog"
+
+	"time"
+
+	clientset "github.com/openebs/zfs-localpv/pkg/generated/clientset/internalclientset"
+	informers "github.com/openebs/zfs-localpv/pkg/generated/informer/externalversions"
+	kubeinformers "k8s.io/client-go/informers"
+	"k8s.io/client-go/kubernetes"
+	"k8s.io/client-go/rest"
+	"k8s.io/client-go/tools/clientcmd"
+)
+
+var (
+	masterURL  string
+	kubeconfig string
+)
+
+// Start starts the zfsrestore controller.
+func Start(controllerMtx *sync.RWMutex, stopCh <-chan struct{}) error {
+
+	// Get in cluster config
+	cfg, err := getClusterConfig(kubeconfig)
+	if err != nil {
+		return errors.Wrap(err, "error building kubeconfig")
+	}
+
+	// Building Kubernetes Clientset
+	kubeClient, err := kubernetes.NewForConfig(cfg)
+	if err != nil {
+		return errors.Wrap(err, "error building kubernetes clientset")
+	}
+
+	// Building OpenEBS Clientset
+	openebsClient, err := clientset.NewForConfig(cfg)
+	if err != nil {
+		return errors.Wrap(err, "error building openebs clientset")
+	}
+
+	kubeInformerFactory := kubeinformers.NewSharedInformerFactory(kubeClient, time.Second*30)
+	bkpInformerFactory := informers.NewSharedInformerFactory(openebsClient, time.Second*30)
+	// Build() fn of all controllers calls AddToScheme to adds all types of this
+	// clientset into the given scheme.
+	// If multiple controllers happen to call this AddToScheme same time,
+	// it causes panic with error saying concurrent map access.
+	// This lock is used to serialize the AddToScheme call of all controllers.
+	controllerMtx.Lock()
+
+	controller, err := NewRstrControllerBuilder().
+		withKubeClient(kubeClient).
+		withOpenEBSClient(openebsClient).
+		withRestoreSynced(bkpInformerFactory).
+		withRestoreLister(bkpInformerFactory).
+		withRecorder(kubeClient).
+		withEventHandler(bkpInformerFactory).
+		withWorkqueueRateLimiting().Build()
+
+	// blocking call, can't use defer to release the lock
+	controllerMtx.Unlock()
+
+	if err != nil {
+		return errors.Wrapf(err, "error building controller instance")
+	}
+
+	go kubeInformerFactory.Start(stopCh)
+	go bkpInformerFactory.Start(stopCh)
+
+	// Threadiness defines the number of workers to be launched in Run function
+	return controller.Run(2, stopCh)
+}
+
+// GetClusterConfig return the config for k8s.
+func getClusterConfig(kubeconfig string) (*rest.Config, error) {
+	cfg, err := rest.InClusterConfig()
+	if err != nil {
+		klog.Errorf("Failed to get k8s Incluster config. %+v", err)
+		if kubeconfig == "" {
+			return nil, errors.Wrap(err, "kubeconfig is empty")
+		}
+		cfg, err = clientcmd.BuildConfigFromFlags(masterURL, kubeconfig)
+		if err != nil {
+			return nil, errors.Wrap(err, "error building kubeconfig")
+		}
+	}
+	return cfg, err
+}