## 0.51.0

* Re-export utils from Starlette:
    * This allows using things like `from fastapi.responses import JSONResponse` instead of `from starlette.responses import JSONResponse`.
    * It's mainly syntax sugar, a convenience for developer experience.

- [`KT-59342`](https://youtrack.jetbrains.com/issue/KT-59342) K2 IDE. FirLazyResolveContractViolationException: `lazyResolveToPhase(TYPES)` cannot be called from a transformer with a phase TYPES

message ConfigMapEnvSource {
  // The ConfigMap to select from.
  optional LocalObjectReference localObjectReference = 1;

  // Specify whether the ConfigMap must be defined
  // +optional
  optional bool optional = 2;
}

// Selects a key from a ConfigMap.
// +structType=atomic
message ConfigMapKeySelector {
  // The ConfigMap to select from.
  optional LocalObjectReference localObjectReference = 1;

  - *apiserver_cache_list_fetched_objects_total*: Counter of objects read from watch cache in the course of serving a LIST request, broken down by resource_prefix and index_name
  - *apiserver_cache_list_evaluated_objects_total*: Counter of objects tested in the course of serving a LIST request from watch cache, broken down by resource_prefix

  - apiserver-advertise-address / apiserver-bind-port: use either localAPIEndpoint from InitConfiguration or controlPlaneEndpoint from ClusterConfiguration.
  - cluster-name: use clusterName from ClusterConfiguration
  - cert-dir: use certificatesDir from ClusterConfiguration ([#94879](https://github.com/kubernetes/kubernetes/pull/94879), [@knight42](https://github.com/knight42)) [SIG Cluster Lifecycle]

registers all of its command-line flags with an internal flagset, which prevents flags from third party libraries from unintentionally leaking into the Kubelet's command-line API. Many unintentionally leaked flags are now marked deprecated, so that users have a chance to migrate away from them before they are removed. In addition, one previously leaked flag, --cloud-provider-gce-lb-src-cidrs, has been entirely removed from the Kubelet's command-line API, because it is irrelevant to Kubelet operation. The...

    * cAdvisor metrics can now be scraped from `/metrics/cadvisor` on the kubelet ports.
    * Note that you have to update your scraping jobs to get kubelet-only metrics from `/metrics` and `container_*` metrics from `/metrics/cadvisor`

    * `kubectl create configmap` has a new option `--from-env-file` that populates a configmap from file which follows a key=val format for each line. ([#38882](https://github.com/kubernetes/kubernetes/pull/38882), [@fraenkel](https://github.com/fraenkel))

    * `kubectl create secret` has a new option `--from-env-file` that populates a secret from file which follows a key=val format for each line.

  * Printing/describe

</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