</p>


<h3 id="Slice_expressions">Slice expressions</h3>

<p>
Slice expressions construct a substring or slice from a string, array, pointer
to array, or slice. There are two variants: a simple form that specifies a low
and high bound, and a full form that also specifies a bound on the capacity.
</p>

<h4>Simple slice expressions</h4>

<p>
The primary expression
</p>

Some upgrade methods might upgrade etcd from 3.0 to 3.1 automatically when you upgrade from Kubernetes 1.8, unless you specify otherwise. Because [etcd does not support downgrading](https://coreos.com/etcd/docs/latest/upgrades/upgrade_3_1.html), you'll need to either remain on etcd 3.1 or restore from a backup if you want to downgrade back to Kubernetes 1.8.

## Introduction to 1.9.0

* fluentd-elasticsearch is unchanged from 1.10: v2.0.4 ([#58525](https://github.com/kubernetes/kubernetes/pull/58525))
* fluentd-gcp is unchanged from 1.10: v3.0.0. ([#60722](https://github.com/kubernetes/kubernetes/pull/60722))
* Ingress glbc is unchanged from 1.10: v1.0.0 ([#61302](https://github.com/kubernetes/kubernetes/pull/61302))
* OIDC authentication is unchanged from 1.10: coreos/go-oidc v2 ([#58544](https://github.com/kubernetes/kubernetes/pull/58544))

- API
  - Ingress resources will no longer be served from `extensions/v1beta1` in v1.19. Migrate use to the `networking.k8s.io/v1beta1` API, available since v1.14. Existing persisted data can be retrieved via the `networking.k8s.io/v1beta1` API.

* kubeadm: fixes error when upgrading from v1.13 to v1.14 clusters created with kubeadm v1.12. Please note that it is required to upgrade etcd during the final v1.13 to v1.14 upgrade. ([#75956](https://github.com/kubernetes/kubernetes/pull/75956), [@fabriziopandini](https://github.com/fabriziopandini))

- Users will see increase in time for deletion of pods and also guarantee that removal of pod from api server  would mean deletion of all the resources from container runtime. ([#92817](https://github.com/kubernetes/kubernetes/pull/92817), [@kmala](https://github.com/kmala)) [SIG Node]

  - `failurePolicy` default changed from `Ignore` to `Fail` for v1
  - `matchPolicy` default changed from `Exact` to `Equivalent` for v1
  - `timeout` default changed from `30s` to `10s` for v1
  - `sideEffects` default value is removed, and the field made required, and only `None` and `NoneOnDryRun` are permitted for v1

 `http_response_size_bytes_sum`
 `http_response_size_bytes_count`
 due to removal from the prometheus client library. Prometheus http request meta-metrics are now generated from [`promhttp.InstrumentMetricHandler`](https://godoc.org/github.com/prometheus/client_golang/prometheus/promhttp#InstrumentMetricHandler) instead.
- Following metrics from kube-controller-manager are now marked as with the ALPHA stability level:

- Kube-apiserver: fixes a 1.27+ regression in watch stability by serving watch requests without a resourceVersion from the watch cache by default, as in <1.27 (disabling the change in #115096 by default). This mitigates the impact of an etcd watch bug (https://github.com/etcd-io/etcd/pull/17555). If the 1.27 change in #115096 to serve these requests from underlying storage is still desired despite the impact on watch stability, it can be re-enabled with a `WatchFromStorageWithoutResourceVersion`...

- `kubeadm`: turned on feature gate `MergeCLIArgumentsWithConfig` to merge the config from flag and config file, otherwise, if the flag `--ignore-preflight-errors` is set from the CLI, then the value from config file will be ignored. ([#119946](https://github.com/kubernetes/kubernetes/pull/119946), [@chendave](https://github.com/chendave))