Map pod names to instance_ids and vice versa

This is a very naive implementation of this maaping: we get all the
pods, sort their names alphabetically and map the sorted names to
ordered indexes. This approach gives us stable mapping but does not
guarantee that during scaling up instance X would be older than instance
X-1

[cloudfoundry/eirini-release#207]

Co-authored-by: Mario Nitchev <[email protected]>

k8s/stset/get.go

@@ -2,12 +2,12 @@ package stset
 
 import (
 	"context"
+	"sort"
 	"strings"
 
 	"code.cloudfoundry.org/eirini"
 	"code.cloudfoundry.org/eirini/api"
 	"code.cloudfoundry.org/eirini/k8s/utils"
-	"code.cloudfoundry.org/eirini/util"
 	"code.cloudfoundry.org/lager"
 	"github.com/pkg/errors"
 	corev1 "k8s.io/api/core/v1"
@@ -73,6 +73,11 @@ func (g *Getter) GetInstances(ctx context.Context, identifier api.LRPIdentifier)
 		return nil, errors.Wrap(err, "failed to list pods")
 	}
 
+	sort.Slice(pods, func(i, j int) bool { return pods[i].Name < pods[j].Name })
+	podToInstanceID := map[string]int{}
+	for i, pod := range pods {
+		podToInstanceID[pod.Name] = i
+	}
 	instances := []*api.Instance{}
 
 	for _, pod := range pods {
@@ -87,7 +92,7 @@ func (g *Getter) GetInstances(ctx context.Context, identifier api.LRPIdentifier)
 			continue
 		}
 
-		index, _ := util.ParseAppIndex(pod.Name)
+		index := podToInstanceID[pod.Name]
 
 		since := int64(0)
 		if pod.Status.StartTime != nil {

k8s/stset/stop.go

@@ -2,12 +2,13 @@ package stset
 
 import (
 	"context"
-	"fmt"
+	"sort"
 
 	"code.cloudfoundry.org/eirini"
 	"code.cloudfoundry.org/eirini/api"
 	"code.cloudfoundry.org/lager"
 	"github.com/pkg/errors"
+	corev1 "k8s.io/api/core/v1"
 	k8serrors "k8s.io/apimachinery/pkg/api/errors"
 	"k8s.io/client-go/util/retry"
 )
@@ -21,6 +22,7 @@ type StatefulSetDeleter interface {
 
 type PodDeleter interface {
 	Delete(ctx context.Context, namespace, name string) error
+	GetByLRPIdentifier(ctx context.Context, id api.LRPIdentifier) ([]corev1.Pod, error)
 }
 
 type Stopper struct {
@@ -97,7 +99,19 @@ func (s *Stopper) StopInstance(ctx context.Context, identifier api.LRPIdentifier
 		return eirini.ErrInvalidInstanceIndex
 	}
 
-	err = s.podDeleter.Delete(ctx, statefulset.Namespace, fmt.Sprintf("%s-%d", statefulset.Name, index))
+	pods, err := s.podDeleter.GetByLRPIdentifier(ctx, identifier)
+	if err != nil {
+		return errors.Wrap(err, "failed to get pods")
+	}
+
+	sort.Slice(pods, func(i, j int) bool { return pods[i].Name < pods[j].Name })
+	indexToPod := map[uint]string{}
+	for i, pod := range pods {
+		indexToPod[uint(i)] = pod.Name
+	}
+
+	podName := indexToPod[index]
+	err = s.podDeleter.Delete(ctx, statefulset.Namespace, podName)
 	if k8serrors.IsNotFound(err) {
 		logger.Debug("pod-does-not-exist")