[VOL-3731] added DeleteWithPrefix method from KV

Provides deleting multiple keys in one shot

Change-Id: I71e3089adcdc90a8307b9503197d220d1405f030
diff --git a/pkg/db/backend.go b/pkg/db/backend.go
index 418bf8e..bf30a48 100644
--- a/pkg/db/backend.go
+++ b/pkg/db/backend.go
@@ -234,6 +234,21 @@
 	return err
 }
 
+// DeleteWithPrefix removes items having prefix key
+func (b *Backend) DeleteWithPrefix(ctx context.Context, prefixKey string) error {
+	span, ctx := log.CreateChildSpan(ctx, "etcd-delete-with-prefix")
+	defer span.Finish()
+
+	formattedPath := b.makePath(ctx, prefixKey)
+	logger.Debugw(ctx, "deleting-prefix-key", log.Fields{"key": prefixKey, "path": formattedPath})
+
+	err := b.Client.DeleteWithPrefix(ctx, formattedPath)
+
+	b.updateLiveness(ctx, b.isErrorIndicatingAliveKvstore(ctx, err))
+
+	return err
+}
+
 // CreateWatch starts watching events for the specified key
 func (b *Backend) CreateWatch(ctx context.Context, key string, withPrefix bool) chan *kvstore.Event {
 	span, ctx := log.CreateChildSpan(ctx, "etcd-create-watch")
diff --git a/pkg/db/kvstore/client.go b/pkg/db/kvstore/client.go
index 2060b06..b35f1f3 100644
--- a/pkg/db/kvstore/client.go
+++ b/pkg/db/kvstore/client.go
@@ -78,6 +78,7 @@
 	Get(ctx context.Context, key string) (*KVPair, error)
 	Put(ctx context.Context, key string, value interface{}) error
 	Delete(ctx context.Context, key string) error
+	DeleteWithPrefix(ctx context.Context, prefixKey string) error
 	Reserve(ctx context.Context, key string, value interface{}, ttl time.Duration) (interface{}, error)
 	ReleaseReservation(ctx context.Context, key string) error
 	ReleaseAllReservations(ctx context.Context) error
diff --git a/pkg/db/kvstore/etcdclient.go b/pkg/db/kvstore/etcdclient.go
index aa5adbf..868b301 100644
--- a/pkg/db/kvstore/etcdclient.go
+++ b/pkg/db/kvstore/etcdclient.go
@@ -157,6 +157,17 @@
 	return nil
 }
 
+func (c *EtcdClient) DeleteWithPrefix(ctx context.Context, prefixKey string) error {
+
+	//delete the prefix
+	if _, err := c.ectdAPI.Delete(ctx, prefixKey, v3Client.WithPrefix()); err != nil {
+		logger.Errorw(ctx, "failed-to-delete-prefix-key", log.Fields{"key": prefixKey, "error": err})
+		return err
+	}
+	logger.Debugw(ctx, "key(s)-deleted", log.Fields{"key": prefixKey})
+	return nil
+}
+
 // Reserve is invoked to acquire a key and set it to a given value. Value can only be a string or []byte since
 // the etcd API accepts only a string.  Timeout defines how long the function will wait for a response.  TTL
 // defines how long that reservation is valid.  When TTL expires the key is unreserved by the KV store itself.