Implements EBS volume resizing #35.

In order to support volumes different from EBS and filesystems other than EXT2/3/4 the respective code parts were implemented as interfaces. Adding the new resize for the volume or the filesystem will require implementing the interface, but no other changes in the cluster code itself.

Volume resizing first changes the EBS and the filesystem, and only afterwards is reflected in the Kubernetes "PersistentVolume" object. This is done deliberately to be able to check if the volume needs resizing by peeking at the Size of the PersistentVolume structure. We recheck, nevertheless, in the EBSVolumeResizer, whether the actual EBS volume size doesn't match the spec, since call to the AWS ModifyVolume is counted against the resize limit of once every 6 hours, even for those calls that shouldn't result in an actual resize (i.e. when the size matches the one for the running volume).

As a collateral, split the constants into multiple files, move the volume code into a separate file and fix minor issues related to the error reporting.

pkg/cluster/cluster.go

@@ -26,6 +26,7 @@ import (
 	"github.com/zalando-incubator/postgres-operator/pkg/util/k8sutil"
 	"github.com/zalando-incubator/postgres-operator/pkg/util/teams"
 	"github.com/zalando-incubator/postgres-operator/pkg/util/users"
+	"github.com/zalando-incubator/postgres-operator/pkg/util/volumes"
 )
 
 var (
@@ -37,6 +38,7 @@ var (
 type Config struct {
 	KubeClient          *kubernetes.Clientset //TODO: move clients to the better place?
 	RestClient          *rest.RESTClient
+	RestConfig          *rest.Config
 	TeamsAPIClient      *teams.API
 	OpConfig            config.Config
 	InfrastructureRoles map[string]spec.PgUser // inherited from the controller
@@ -68,6 +70,13 @@ type Cluster struct {
 	podEventsQueue   *cache.FIFO
 }
 
+type compareStatefulsetResult struct {
+	match         bool
+	replace       bool
+	rollingUpdate bool
+	reasons       []string
+}
+
 func New(cfg Config, pgSpec spec.Postgresql, logger *logrus.Entry) *Cluster {
 	lg := logger.WithField("pkg", "cluster").WithField("cluster-name", pgSpec.Metadata.Name)
 	kubeResources := kubeResources{Secrets: make(map[types.UID]*v1.Secret)}
@@ -244,20 +253,24 @@ func (c *Cluster) sameVolumeWith(volume spec.Volume) (match bool, reason string)
 	return
 }
 
-func (c *Cluster) compareStatefulSetWith(statefulSet *v1beta1.StatefulSet) (match, needsReplace, needsRollUpdate bool, reason string) {
+func (c *Cluster) compareStatefulSetWith(statefulSet *v1beta1.StatefulSet) *compareStatefulsetResult {
+	reasons := make([]string, 0)
+	var match, needsRollUpdate, needsReplace bool
+
 	match = true
 	//TODO: improve me
 	if *c.Statefulset.Spec.Replicas != *statefulSet.Spec.Replicas {
 		match = false
-		reason = "new statefulset's number of replicas doesn't match the current one"
+		reasons = append(reasons, "new statefulset's number of replicas doesn't match the current one")
 	}
 	if len(c.Statefulset.Spec.Template.Spec.Containers) != len(statefulSet.Spec.Template.Spec.Containers) {
 		needsRollUpdate = true
-		reason = "new statefulset's container specification doesn't match the current one"
+		reasons = append(reasons, "new statefulset's container specification doesn't match the current one")
 	}
 	if len(c.Statefulset.Spec.Template.Spec.Containers) == 0 {
+
 		c.logger.Warnf("statefulset '%s' has no container", util.NameFromMeta(c.Statefulset.ObjectMeta))
-		return
+		return &compareStatefulsetResult{}
 	}
 	// In the comparisons below, the needsReplace and needsRollUpdate flags are never reset, since checks fall through
 	// and the combined effect of all the changes should be applied.
@@ -267,48 +280,44 @@ func (c *Cluster) compareStatefulSetWith(statefulSet *v1beta1.StatefulSet) (matc
 	if c.Statefulset.Spec.Template.Spec.ServiceAccountName != statefulSet.Spec.Template.Spec.ServiceAccountName {
 		needsReplace = true
 		needsRollUpdate = true
-		reason = "new statefulset's serviceAccountName service asccount name doesn't match the current one"
+		reasons = append(reasons, "new statefulset's serviceAccountName service asccount name doesn't match the current one")
 	}
 	if *c.Statefulset.Spec.Template.Spec.TerminationGracePeriodSeconds != *statefulSet.Spec.Template.Spec.TerminationGracePeriodSeconds {
 		needsReplace = true
 		needsRollUpdate = true
-		reason = "new statefulset's terminationGracePeriodSeconds  doesn't match the current one"
+		reasons = append(reasons, "new statefulset's terminationGracePeriodSeconds  doesn't match the current one")
 	}
 	// Some generated fields like creationTimestamp make it not possible to use DeepCompare on Spec.Template.ObjectMeta
 	if !reflect.DeepEqual(c.Statefulset.Spec.Template.Labels, statefulSet.Spec.Template.Labels) {
 		needsReplace = true
 		needsRollUpdate = true
-		reason = "new statefulset's metadata labels doesn't match the current one"
+		reasons = append(reasons, "new statefulset's metadata labels doesn't match the current one")
 	}
 	if !reflect.DeepEqual(c.Statefulset.Spec.Template.Annotations, statefulSet.Spec.Template.Annotations) {
 		needsRollUpdate = true
 		needsReplace = true
-		reason = "new statefulset's metadata annotations doesn't match the current one"
+		reasons = append(reasons, "new statefulset's metadata annotations doesn't match the current one")
 	}
 	if len(c.Statefulset.Spec.VolumeClaimTemplates) != len(statefulSet.Spec.VolumeClaimTemplates) {
 		needsReplace = true
-		needsRollUpdate = true
-		reason = "new statefulset's volumeClaimTemplates contains different number of volumes to the old one"
+		reasons = append(reasons, "new statefulset's volumeClaimTemplates contains different number of volumes to the old one")
 	}
 	for i := 0; i < len(c.Statefulset.Spec.VolumeClaimTemplates); i++ {
 		name := c.Statefulset.Spec.VolumeClaimTemplates[i].Name
 		// Some generated fields like creationTimestamp make it not possible to use DeepCompare on ObjectMeta
 		if name != statefulSet.Spec.VolumeClaimTemplates[i].Name {
 			needsReplace = true
-			needsRollUpdate = true
-			reason = fmt.Sprintf("new statefulset's name for volume %d doesn't match the current one", i)
+			reasons = append(reasons, fmt.Sprintf("new statefulset's name for volume %d doesn't match the current one", i))
 			continue
 		}
 		if !reflect.DeepEqual(c.Statefulset.Spec.VolumeClaimTemplates[i].Annotations, statefulSet.Spec.VolumeClaimTemplates[i].Annotations) {
 			needsReplace = true
-			needsRollUpdate = true
-			reason = fmt.Sprintf("new statefulset's annotations for volume %s doesn't match the current one", name)
+			reasons = append(reasons, fmt.Sprintf("new statefulset's annotations for volume %s doesn't match the current one", name))
 		}
 		if !reflect.DeepEqual(c.Statefulset.Spec.VolumeClaimTemplates[i].Spec, statefulSet.Spec.VolumeClaimTemplates[i].Spec) {
 			name := c.Statefulset.Spec.VolumeClaimTemplates[i].Name
 			needsReplace = true
-			needsRollUpdate = true
-			reason = fmt.Sprintf("new statefulset's volumeClaimTemplates specification for volume %s doesn't match the current one", name)
+			reasons = append(reasons, fmt.Sprintf("new statefulset's volumeClaimTemplates specification for volume %s doesn't match the current one", name))
 		}
 	}
 
@@ -316,28 +325,27 @@ func (c *Cluster) compareStatefulSetWith(statefulSet *v1beta1.StatefulSet) (matc
 	container2 := statefulSet.Spec.Template.Spec.Containers[0]
 	if container1.Image != container2.Image {
 		needsRollUpdate = true
-		reason = "new statefulset's container image doesn't match the current one"
+		reasons = append(reasons, "new statefulset's container image doesn't match the current one")
 	}
 
 	if !reflect.DeepEqual(container1.Ports, container2.Ports) {
 		needsRollUpdate = true
-		reason = "new statefulset's container ports don't match the current one"
+		reasons = append(reasons, "new statefulset's container ports don't match the current one")
 	}
 
 	if !compareResources(&container1.Resources, &container2.Resources) {
 		needsRollUpdate = true
-		reason = "new statefulset's container resources don't match the current ones"
+		reasons = append(reasons, "new statefulset's container resources don't match the current ones")
 	}
 	if !reflect.DeepEqual(container1.Env, container2.Env) {
 		needsRollUpdate = true
-		reason = "new statefulset's container environment doesn't match the current one"
+		reasons = append(reasons, "new statefulset's container environment doesn't match the current one")
 	}
 
 	if needsRollUpdate || needsReplace {
 		match = false
 	}
-
-	return
+	return &compareStatefulsetResult{match: match, reasons: reasons, rollingUpdate: needsRollUpdate, replace: needsReplace}
 }
 
 func compareResources(a *v1.ResourceRequirements, b *v1.ResourceRequirements) (equal bool) {
@@ -387,22 +395,16 @@ func (c *Cluster) Update(newSpec *spec.Postgresql) error {
 		c.logger.Infof("service '%s' has been updated", util.NameFromMeta(c.Service.ObjectMeta))
 	}
 
-	if match, reason := c.sameVolumeWith(newSpec.Spec.Volume); !match {
-		c.logVolumeChanges(c.Spec.Volume, newSpec.Spec.Volume, reason)
-		//TODO: update PVC
-	}
-
 	newStatefulSet, err := c.genStatefulSet(newSpec.Spec)
 	if err != nil {
 		return fmt.Errorf("could not generate statefulset: %v", err)
 	}
+	cmp := c.compareStatefulSetWith(newStatefulSet)
 
-	sameSS, needsReplace, rollingUpdate, reason := c.compareStatefulSetWith(newStatefulSet)
-
-	if !sameSS {
-		c.logStatefulSetChanges(c.Statefulset, newStatefulSet, true, reason)
+	if !cmp.match {
+		c.logStatefulSetChanges(c.Statefulset, newStatefulSet, true, cmp.reasons)
 		//TODO: mind the case of updating allowedSourceRanges
-		if !needsReplace {
+		if !cmp.replace {
 			if err := c.updateStatefulSet(newStatefulSet); err != nil {
 				c.setStatus(spec.ClusterStatusUpdateFailed)
 				return fmt.Errorf("could not upate statefulset: %v", err)
@@ -423,7 +425,7 @@ func (c *Cluster) Update(newSpec *spec.Postgresql) error {
 		//TODO: rewrite pg version in tpr spec
 	}
 
-	if rollingUpdate {
+	if cmp.rollingUpdate {
 		c.logger.Infof("Rolling update is needed")
 		// TODO: wait for actual streaming to the replica
 		if err := c.recreatePods(); err != nil {
@@ -432,6 +434,15 @@ func (c *Cluster) Update(newSpec *spec.Postgresql) error {
 		}
 		c.logger.Infof("Rolling update has been finished")
 	}
+
+	if match, reason := c.sameVolumeWith(newSpec.Spec.Volume); !match {
+		c.logVolumeChanges(c.Spec.Volume, newSpec.Spec.Volume, reason)
+		if err := c.resizeVolumes(newSpec.Spec.Volume, []volumes.VolumeResizer{&volumes.EBSVolumeResizer{}}); err != nil {
+			return fmt.Errorf("Could not update volumes: %v", err)
+		}
+		c.logger.Infof("volumes have been updated successfully")
+	}
+
 	c.setStatus(spec.ClusterStatusRunning)
 
 	return nil

pkg/cluster/exec.go

@@ -0,0 +1,61 @@
+package cluster
+
+import (
+	"bytes"
+	"fmt"
+
+	remotecommandconsts "k8s.io/apimachinery/pkg/util/remotecommand"
+	"k8s.io/client-go/pkg/api"
+	"k8s.io/kubernetes/pkg/client/unversioned/remotecommand"
+
+	"github.com/zalando-incubator/postgres-operator/pkg/spec"
+)
+
+func (c *Cluster) ExecCommand(podName *spec.NamespacedName, command ...string) (string, error) {
+	var (
+		execOut bytes.Buffer
+		execErr bytes.Buffer
+	)
+
+	pod, err := c.KubeClient.Pods(podName.Namespace).Get(podName.Name)
+	if err != nil {
+		return "", fmt.Errorf("could not get pod info: %v", err)
+	}
+
+	if len(pod.Spec.Containers) != 1 {
+		return "", fmt.Errorf("could not determine which container to use")
+	}
+
+	req := c.RestClient.Post().
+		Resource("pods").
+		Name(podName.Name).
+		Namespace(podName.Namespace).
+		SubResource("exec")
+	req.VersionedParams(&api.PodExecOptions{
+		Container: pod.Spec.Containers[0].Name,
+		Command:   command,
+		Stdout:    true,
+		Stderr:    true,
+	}, api.ParameterCodec)
+
+	exec, err := remotecommand.NewExecutor(c.RestConfig, "POST", req.URL())
+	if err != nil {
+		return "", fmt.Errorf("failed to init executor: %v", err)
+	}
+
+	err = exec.Stream(remotecommand.StreamOptions{
+		SupportedProtocols: remotecommandconsts.SupportedStreamingProtocols,
+		Stdout:             &execOut,
+		Stderr:             &execErr,
+	})
+
+	if err != nil {
+		return "", fmt.Errorf("could not execute: %v", err)
+	}
+
+	if execErr.Len() > 0 {
+		return "", fmt.Errorf("stderr: %v", execErr.String())
+	}
+
+	return execOut.String(), nil
+}

pkg/cluster/filesystems.go

@@ -0,0 +1,46 @@
+package cluster
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/zalando-incubator/postgres-operator/pkg/spec"
+	"github.com/zalando-incubator/postgres-operator/pkg/util/constants"
+	"github.com/zalando-incubator/postgres-operator/pkg/util/filesystems"
+)
+
+func (c *Cluster) getPostgresFilesystemInfo(podName *spec.NamespacedName) (device, fstype string, err error) {
+	out, err := c.ExecCommand(podName, "bash", "-c", fmt.Sprintf("df -T %s|tail -1", constants.PostgresDataMount))
+	if err != nil {
+		return "", "", err
+	}
+	fields := strings.Fields(out)
+	if len(fields) < 2 {
+		return "", "", fmt.Errorf("too few fields in the df output")
+	}
+
+	return fields[0], fields[1], nil
+}
+
+func (c *Cluster) resizePostgresFilesystem(podName *spec.NamespacedName, resizers []filesystems.FilesystemResizer) error {
+	// resize2fs always writes to stderr, and ExecCommand considers a non-empty stderr an error
+	// first, determine the device and the filesystem
+	deviceName, fsType, err := c.getPostgresFilesystemInfo(podName)
+	if err != nil {
+		return fmt.Errorf("could not get device and type for the postgres filesystem: %v", err)
+	}
+	for _, resizer := range resizers {
+		if !resizer.CanResizeFilesystem(fsType) {
+			continue
+		}
+		err := resizer.ResizeFilesystem(deviceName, func(cmd string) (out string, err error) {
+			return c.ExecCommand(podName, "bash", "-c", cmd)
+		})
+
+		if err != nil {
+			return err
+		}
+		return nil
+	}
+	return fmt.Errorf("could not resize filesystem: no compatible resizers for the filesystem of type %s", fsType)
+}

pkg/cluster/k8sres.go

@@ -213,7 +213,7 @@ func (c *Cluster) genPodTemplate(resourceRequirements *v1.ResourceRequirements,
 		},
 		{
 			Name:  "PGROOT",
-			Value: "/home/postgres/pgdata/pgroot",
+			Value: constants.PostgresDataPath,
 		},
 		{
 			Name:  "ETCD_HOST",
@@ -293,7 +293,7 @@ func (c *Cluster) genPodTemplate(resourceRequirements *v1.ResourceRequirements,
 		VolumeMounts: []v1.VolumeMount{
 			{
 				Name:      constants.DataVolumeName,
-				MountPath: "/home/postgres/pgdata", //TODO: fetch from manifesto
+				MountPath: constants.PostgresDataMount, //TODO: fetch from manifesto
 			},
 		},
 		Env: envVars,

pkg/cluster/pod.go

@@ -24,19 +24,6 @@ func (c *Cluster) listPods() ([]v1.Pod, error) {
 	return pods.Items, nil
 }
 
-func (c *Cluster) listPersistentVolumeClaims() ([]v1.PersistentVolumeClaim, error) {
-	ns := c.Metadata.Namespace
-	listOptions := v1.ListOptions{
-		LabelSelector: c.labelsSet().String(),
-	}
-
-	pvcs, err := c.KubeClient.PersistentVolumeClaims(ns).List(listOptions)
-	if err != nil {
-		return nil, fmt.Errorf("could not get list of PersistentVolumeClaims: %v", err)
-	}
-	return pvcs.Items, nil
-}
-
 func (c *Cluster) deletePods() error {
 	c.logger.Debugln("Deleting pods")
 	pods, err := c.listPods()
@@ -63,28 +50,6 @@ func (c *Cluster) deletePods() error {
 	return nil
 }
 
-func (c *Cluster) deletePersistenVolumeClaims() error {
-	c.logger.Debugln("Deleting PVCs")
-	ns := c.Metadata.Namespace
-	pvcs, err := c.listPersistentVolumeClaims()
-	if err != nil {
-		return err
-	}
-	for _, pvc := range pvcs {
-		c.logger.Debugf("Deleting PVC '%s'", util.NameFromMeta(pvc.ObjectMeta))
-		if err := c.KubeClient.PersistentVolumeClaims(ns).Delete(pvc.Name, c.deleteOptions); err != nil {
-			c.logger.Warningf("could not delete PersistentVolumeClaim: %v", err)
-		}
-	}
-	if len(pvcs) > 0 {
-		c.logger.Debugln("PVCs have been deleted")
-	} else {
-		c.logger.Debugln("No PVCs to delete")
-	}
-
-	return nil
-}
-
 func (c *Cluster) deletePod(podName spec.NamespacedName) error {
 	ch := c.registerPodSubscriber(podName)
 	defer c.unregisterPodSubscriber(podName)

pkg/cluster/sync.go

@@ -5,6 +5,7 @@ import (
 
 	"github.com/zalando-incubator/postgres-operator/pkg/util"
 	"github.com/zalando-incubator/postgres-operator/pkg/util/k8sutil"
+	"github.com/zalando-incubator/postgres-operator/pkg/util/volumes"
 )
 
 func (c *Cluster) Sync() error {
@@ -44,18 +45,22 @@ func (c *Cluster) Sync() error {
 		}
 	}
 
-	if c.databaseAccessDisabled() {
-		return nil
-	}
-	if err := c.initDbConn(); err != nil {
-		return fmt.Errorf("could not init db connection: %v", err)
-	} else {
-		c.logger.Debugf("Syncing roles")
-		if err := c.SyncRoles(); err != nil {
-			return fmt.Errorf("could not sync roles: %v", err)
+	if !c.databaseAccessDisabled() {
+		if err := c.initDbConn(); err != nil {
+			return fmt.Errorf("could not init db connection: %v", err)
+		} else {
+			c.logger.Debugf("Syncing roles")
+			if err := c.SyncRoles(); err != nil {
+				return fmt.Errorf("could not sync roles: %v", err)
+			}
 		}
 	}
 
+	c.logger.Debugf("Syncing persistent volumes")
+	if err := c.SyncVolumes(); err != nil {
+		return fmt.Errorf("could not sync persistent volumes: %v", err)
+	}
+
 	return nil
 }
 
@@ -114,7 +119,7 @@ func (c *Cluster) syncEndpoint() error {
 
 func (c *Cluster) syncStatefulSet() error {
 	cSpec := c.Spec
-	var rollUpdate, needsReplace bool
+	var rollUpdate bool
 	if c.Statefulset == nil {
 		c.logger.Infof("could not find the cluster's statefulset")
 		pods, err := c.listPods()
@@ -139,24 +144,20 @@ func (c *Cluster) syncStatefulSet() error {
 			return nil
 		}
 	}
+	/* TODO: should check that we need to replace the statefulset */
 	if !rollUpdate {
-		var (
-			match  bool
-			reason string
-		)
-
 		desiredSS, err := c.genStatefulSet(cSpec)
 		if err != nil {
 			return fmt.Errorf("could not generate statefulset: %v", err)
 		}
 
-		match, needsReplace, rollUpdate, reason = c.compareStatefulSetWith(desiredSS)
-		if match {
+		cmp := c.compareStatefulSetWith(desiredSS)
+		if cmp.match {
 			return nil
 		}
-		c.logStatefulSetChanges(c.Statefulset, desiredSS, false, reason)
+		c.logStatefulSetChanges(c.Statefulset, desiredSS, false, cmp.reasons)
 
-		if !needsReplace {
+		if !cmp.replace {
 			if err := c.updateStatefulSet(desiredSS); err != nil {
 				return fmt.Errorf("could not update statefulset: %v", err)
 			}
@@ -166,7 +167,7 @@ func (c *Cluster) syncStatefulSet() error {
 			}
 		}
 
-		if !rollUpdate {
+		if !cmp.rollingUpdate {
 			c.logger.Debugln("No rolling update is needed")
 			return nil
 		}
@@ -199,3 +200,19 @@ func (c *Cluster) SyncRoles() error {
 	}
 	return nil
 }
+
+/* SyncVolume reads all persistent volumes and checks that their size matches the one declared in the statefulset */
+func (c *Cluster) SyncVolumes() error {
+	act, err := c.VolumesNeedResizing(c.Spec.Volume)
+	if err != nil {
+		return fmt.Errorf("could not compare size of the volumes: %v", err)
+	}
+	if !act {
+		return nil
+	}
+	if err := c.resizeVolumes(c.Spec.Volume, []volumes.VolumeResizer{&volumes.EBSVolumeResizer{}}); err != nil {
+		return fmt.Errorf("Could not sync volumes: %v", err)
+	}
+	c.logger.Infof("volumes have been synced successfully")
+	return nil
+}

pkg/cluster/util.go

@@ -63,7 +63,7 @@ func specPatch(spec interface{}) ([]byte, error) {
 	}{spec})
 }
 
-func (c *Cluster) logStatefulSetChanges(old, new *v1beta1.StatefulSet, isUpdate bool, reason string) {
+func (c *Cluster) logStatefulSetChanges(old, new *v1beta1.StatefulSet, isUpdate bool, reasons []string) {
 	if isUpdate {
 		c.logger.Infof("statefulset '%s' has been changed",
 			util.NameFromMeta(old.ObjectMeta),
@@ -75,8 +75,10 @@ func (c *Cluster) logStatefulSetChanges(old, new *v1beta1.StatefulSet, isUpdate
 	}
 	c.logger.Debugf("diff\n%s\n", util.PrettyDiff(old.Spec, new.Spec))
 
-	if reason != "" {
-		c.logger.Infof("Reason: %s", reason)
+	if len(reasons) > 0 {
+		for _, reason := range reasons {
+			c.logger.Infof("Reason: %s", reason)
+		}
 	}
 }
 

pkg/cluster/volumes.go

@@ -0,0 +1,178 @@
+package cluster
+
+import (
+	"fmt"
+	"strconv"
+	"strings"
+
+	"k8s.io/client-go/pkg/api/resource"
+	"k8s.io/client-go/pkg/api/v1"
+
+	"github.com/zalando-incubator/postgres-operator/pkg/spec"
+	"github.com/zalando-incubator/postgres-operator/pkg/util"
+	"github.com/zalando-incubator/postgres-operator/pkg/util/constants"
+	"github.com/zalando-incubator/postgres-operator/pkg/util/filesystems"
+	"github.com/zalando-incubator/postgres-operator/pkg/util/volumes"
+)
+
+func (c *Cluster) listPersistentVolumeClaims() ([]v1.PersistentVolumeClaim, error) {
+	ns := c.Metadata.Namespace
+	listOptions := v1.ListOptions{
+		LabelSelector: c.labelsSet().String(),
+	}
+
+	pvcs, err := c.KubeClient.PersistentVolumeClaims(ns).List(listOptions)
+	if err != nil {
+		return nil, fmt.Errorf("could not list of PersistentVolumeClaims: %v", err)
+	}
+	return pvcs.Items, nil
+}
+
+func (c *Cluster) deletePersistenVolumeClaims() error {
+	c.logger.Debugln("Deleting PVCs")
+	pvcs, err := c.listPersistentVolumeClaims()
+	if err != nil {
+		return err
+	}
+	for _, pvc := range pvcs {
+		c.logger.Debugf("Deleting PVC '%s'", util.NameFromMeta(pvc.ObjectMeta))
+		if err := c.KubeClient.PersistentVolumeClaims(pvc.Namespace).Delete(pvc.Name, c.deleteOptions); err != nil {
+			c.logger.Warningf("could not delete PersistentVolumeClaim: %v", err)
+		}
+	}
+	if len(pvcs) > 0 {
+		c.logger.Debugln("PVCs have been deleted")
+	} else {
+		c.logger.Debugln("No PVCs to delete")
+	}
+
+	return nil
+}
+
+func (c *Cluster) listPersistentVolumes() ([]*v1.PersistentVolume, error) {
+	result := make([]*v1.PersistentVolume, 0)
+
+	pvcs, err := c.listPersistentVolumeClaims()
+	if err != nil {
+		return nil, fmt.Errorf("could not list cluster's PersistentVolumeClaims: %v", err)
+	}
+	lastPodIndex := *c.Statefulset.Spec.Replicas - 1
+	for _, pvc := range pvcs {
+		lastDash := strings.LastIndex(pvc.Name, "-")
+		if lastDash > 0 && lastDash < len(pvc.Name)-1 {
+			if pvcNumber, err := strconv.Atoi(pvc.Name[lastDash+1:]); err != nil {
+				return nil, fmt.Errorf("could not convert last part of the persistent volume claim name %s to a number", pvc.Name)
+			} else {
+				if int32(pvcNumber) > lastPodIndex {
+					c.logger.Debugf("Skipping persistent volume %s corresponding to a non-running pods", pvc.Name)
+					continue
+				}
+			}
+
+		}
+		pv, err := c.KubeClient.PersistentVolumes().Get(pvc.Spec.VolumeName)
+		if err != nil {
+			return nil, fmt.Errorf("could not get PersistentVolume: %v", err)
+		}
+		result = append(result, pv)
+	}
+
+	return result, nil
+}
+
+// resizeVolumes resize persistent volumes compatible with the given resizer interface
+func (c *Cluster) resizeVolumes(newVolume spec.Volume, resizers []volumes.VolumeResizer) error {
+	totalCompatible := 0
+	newQuantity, err := resource.ParseQuantity(newVolume.Size)
+	if err != nil {
+		return fmt.Errorf("could not parse volume size: %v", err)
+	}
+	pvs, newSize, err := c.listVolumesWithManifestSize(newVolume)
+	if err != nil {
+		return fmt.Errorf("could not list persistent volumes: %v", err)
+	}
+	for _, pv := range pvs {
+		volumeSize := quantityToGigabyte(pv.Spec.Capacity[v1.ResourceStorage])
+		if volumeSize > newSize {
+			return fmt.Errorf("cannot shrink persistent volume")
+		}
+		if volumeSize == newSize {
+			continue
+		}
+		for _, resizer := range resizers {
+			if !resizer.VolumeBelongsToProvider(pv) {
+				continue
+			}
+			totalCompatible += 1
+			if !resizer.IsConnectedToProvider() {
+				err := resizer.ConnectToProvider()
+				if err != nil {
+					return fmt.Errorf("could not connect to the volume provider: %v", err)
+				}
+				defer resizer.DisconnectFromProvider()
+			}
+			awsVolumeId, err := resizer.GetProviderVolumeID(pv)
+			if err != nil {
+				return err
+			}
+			c.logger.Debugf("updating persistent volume %s to %d", pv.Name, newSize)
+			if err := resizer.ResizeVolume(awsVolumeId, newSize); err != nil {
+				return fmt.Errorf("could not resize EBS volume %s: %v", awsVolumeId, err)
+			}
+			c.logger.Debugf("resizing the filesystem on the volume %s", pv.Name)
+			podName := getPodNameFromPersistentVolume(pv)
+			if err := c.resizePostgresFilesystem(podName, []filesystems.FilesystemResizer{&filesystems.Ext234Resize{}}); err != nil {
+				return fmt.Errorf("could not resize the filesystem on pod '%s': %v", podName, err)
+			}
+			c.logger.Debugf("filesystem resize successfull on volume %s", pv.Name)
+			pv.Spec.Capacity[v1.ResourceStorage] = newQuantity
+			c.logger.Debugf("updating persistent volume definition for volume %s", pv.Name)
+			if _, err := c.KubeClient.PersistentVolumes().Update(pv); err != nil {
+				return fmt.Errorf("could not update persistent volume: %s", err)
+			}
+			c.logger.Debugf("successfully updated persistent volume %s", pv.Name)
+		}
+	}
+	if len(pvs) > 0 && totalCompatible == 0 {
+		return fmt.Errorf("could not resize EBS volumes: persistent volumes are not compatible with existing resizing providers")
+	}
+	return nil
+}
+
+func (c *Cluster) VolumesNeedResizing(newVolume spec.Volume) (bool, error) {
+	volumes, manifestSize, err := c.listVolumesWithManifestSize(newVolume)
+	if err != nil {
+		return false, err
+	}
+	for _, pv := range volumes {
+		currentSize := quantityToGigabyte(pv.Spec.Capacity[v1.ResourceStorage])
+		if currentSize != manifestSize {
+			return true, nil
+		}
+	}
+	return false, nil
+}
+
+func (c *Cluster) listVolumesWithManifestSize(newVolume spec.Volume) ([]*v1.PersistentVolume, int64, error) {
+	newSize, err := resource.ParseQuantity(newVolume.Size)
+	if err != nil {
+		return nil, 0, fmt.Errorf("could not parse volume size from the manifest: %v", err)
+	}
+	manifestSize := quantityToGigabyte(newSize)
+	volumes, err := c.listPersistentVolumes()
+	if err != nil {
+		return nil, 0, fmt.Errorf("could not list persistent volumes: %v", err)
+	}
+	return volumes, manifestSize, nil
+}
+
+// getPodNameFromPersistentVolume returns a pod name that it extracts from the volume claim ref.
+func getPodNameFromPersistentVolume(pv *v1.PersistentVolume) *spec.NamespacedName {
+	namespace := pv.Spec.ClaimRef.Namespace
+	name := pv.Spec.ClaimRef.Name[len(constants.DataVolumeName)+1:]
+	return &spec.NamespacedName{namespace, name}
+}
+
+func quantityToGigabyte(q resource.Quantity) int64 {
+	return q.ScaledValue(0) / (1 * constants.Gigabyte)
+}