*   Iterator<E> it = set2.descendingIterator();
   *   while (it.hasNext()) {
   *     foo(it.next());
   *   }
   * }
   * }
   *
   * <p>Failure to follow this advice may result in non-deterministic behavior.
   *
   * <p>The returned navigable set will be serializable if the specified navigable set is
   * serializable.
   *

 * misleading to future readers of the code and of stack traces. See <a
 * href="https://github.com/google/guava/wiki/ConditionalFailuresExplained">Conditional failures
 * explained</a> in the Guava User Guide for more advice. Notably, {@link Verify} offers assertions
 * similar to those in this class for non-precondition checks.
 *
 * <h3>{@code java.util.Objects.requireNonNull()}</h3>
 *

   *   Iterator<V> i = values.iterator(); // Must be in synchronized block
   *   while (i.hasNext()) {
   *     foo(i.next());
   *   }
   * }
   * }
   *
   * <p>Failure to follow this advice may result in non-deterministic behavior.
   *
   * <p>Note that the generated multimap's {@link Multimap#removeAll} and {@link
   * Multimap#replaceValues} methods return collections that aren't synchronized.
   *

   *   Iterator<V> i = values.iterator(); // Must be in synchronized block
   *   while (i.hasNext()) {
   *     foo(i.next());
   *   }
   * }
   * }
   *
   * <p>Failure to follow this advice may result in non-deterministic behavior.
   *
   * <p>Note that the generated multimap's {@link Multimap#removeAll} and {@link
   * Multimap#replaceValues} methods return collections that aren't synchronized.
   *

immediately after upgrading. In multi-tenant clusters where not all users are trusted, you are advised to create appropriate quotas for two default priority classes, system-cluster-critical and system-node-critical, which are added to clusters by default. `ResourceQuota` should be created to limit users from creating Pods at these priorities if not all users of your cluster are trusted. We do not advise disabling this feature because critical system Pods rely on the scheduler preemption to be scheduled...

- The `--cidr-allocator-type` option set to `CloudAllocator` for `kube-controller-manager` will be deprecated and removed in a future release. Users are advised to transition to and explore the available options provided by their external cloud provider. ([#123011](https://github.com/kubernetes/kubernetes/pull/123011), [@dims](https://github.com/dims))

- Kube-proxy will no longer hold service node ports open on the node. Users are still advised not to run any listener on node ports range used by kube-proxy. ([#108496](https://github.com/kubernetes/kubernetes/pull/108496), [@khenidak](https://github.com/khenidak))

### kube-proxy
* In 1.7, the kube-proxy component has been converted to use a configuration file. The old flags still work in 1.7, but they are being deprecated and will be removed in a future release. Cluster administrators are advised to switch to using the configuration file, but no action is strictly necessary in 1.7. ([#34727](https://github.com/kubernetes/kubernetes/pull/34727), [@ncdc](https://github.com/ncdc))

### Namespace

Before updating to 1.6, you are strongly recommended to back up your etcd data.
Please consult the installation procedure you are using (kargo, kops, kube-up,
kube-aws, kubeadm etc) for specific advice.

1.6 encourages etcd3, and switching from etcd2 to etcd3 involves a full
migration of data between different storage engines.  You must stop the API

## WARNING: etcd backup strongly recommended

Before updating to 1.9, you are strongly recommended to back up your etcd data. Consult the installation procedure you are using (kargo, kops, kube-up, kube-aws, kubeadm etc) for specific advice.