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;

## 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.

 `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:

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...

* 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))

* etcd2: watching from 0 returns all initial states as ADDED events ([#38079](https://github.com/kubernetes/kubernetes/pull/38079), [@hongchao...

- `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))

    * `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

- Upon receiving a LIST request with an expired continue token, the apiserver now returns a continue token together with the 410 "the from parameter is too old" error. If the client does not care about getting a list from a consistent snapshot, the client can use this token to continue listing from the next key, but the returned chunk will be from the latest snapshot. ([#67284](https://github.com/kubernetes/kubernetes/pull/67284), [@caesarxuchao](https://github.com/caesarxuchao))

  - *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