// Variable references $(VAR_NAME) are expanded using the container's environment. If a variable
  // cannot be resolved, the reference in the input string will be unchanged. Double $$ are reduced
  // to a single $, which allows for escaping the $(VAR_NAME) syntax: i.e. "$$(VAR_NAME)" will
  // produce the string literal "$(VAR_NAME)". Escaped references will never be expanded, regardless

### Bug or Regression

    /** The key of the configuration. e.g. 5 */
    String INDEX_number_of_shards = "index.number_of_shards";

    /** The key of the configuration. e.g. 0-1 */
    String INDEX_auto_expand_replicas = "index.auto_expand_replicas";

    /** The key of the configuration. e.g. SHA-512 */
    String INDEX_ID_DIGEST_ALGORITHM = "index.id.digest.algorithm";

    /** The key of the configuration. e.g. admin */

- In some cases, a Flex volume resize may leave a PVC with erroneous Resizing condition even after volume has been successfully expanded. Users may choose to delete the condition, but it is not required. ([#71470](https://github.com/kubernetes/kubernetes/issues/71470))

## Changelog since v1.17.13

## Changes by Kind

### Bug or Regression

- Persistent Volumes formatted with the btrfs filesystem will now automatically resize when expanded. ([#99361](https://github.com/kubernetes/kubernetes/pull/99361), [@Novex](https://github.com/Novex)) [SIG Storage]

* Updated AWS SDK to v1.16.26 for ECR PrivateLink support ([#73435](https://github.com/kubernetes/kubernetes/pull/73435), [@micahhausler](https://github.com/micahhausler))
* Expand kubectl wait to work with more types of selectors. ([#71746](https://github.com/kubernetes/kubernetes/pull/71746), [@rctl](https://github.com/rctl))

- Add a namespace label for all `apiserver_admission_* metrics`.
  Expand the histogram range to 0-10s for all `apiserver_admission_*_duration_seconds` metrics. ([#101208](https://github.com/kubernetes/kubernetes/pull/101208), [@voutcn](https://github.com/voutcn))

- Alter wording to describe pods using a pvc ([#95635](https://github.com/kubernetes/kubernetes/pull/95635), [@RaunakShah](https://github.com/RaunakShah)) [SIG CLI]

### Autoscaling
* Introduces an new alpha version of the Horizontal Pod Autoscaler including expanded support for specifying metrics. ([#36033](https://github.com/kubernetes/kubernetes/pull/36033), [@DirectXMan12](https://github.com/DirectXMan12)