- Kubeadm: apply further improvements to the tentative support for concurrent etcd member join. Fixes a bug where multiple members can receive the same hostname. Increase the etcd client dial timeout and retry timeout for add/remove/... operations. ([#87505](https://github.com/kubernetes/kubernetes/pull/87505), [@neolit123](https://github.com/neolit123)) [SIG...

          "google.com",
          "home.netscape.com",
          "it-trace.ch",
          "jobs.kt.com.",
          "jprs.co.jp",
          "kt.co",
          "ledger-enquirer.com",
          "members.blah.nl.",
          "pvt.k12.ca.us",
          "site.ac.jp",
          "site.ad.jp",
          "site.cc",
          "site.ed.jp",
          "site.ee",
          "site.fi",
          "site.fm",

* If the cluster node count exceeds the GCE TargetPool maximum (currently 1000), ([#25178](https://github.com/kubernetes/kubernetes/pull/25178), [@zmerlynn](https://github.com/zmerlynn))
    * randomly select which nodes are members of Kubernetes External Load Balancers.
* Clarify supported version skew between masters, nodes, and clients ([#25087](https://github.com/kubernetes/kubernetes/pull/25087), [@ihmccreery](https://github.com/ihmccreery))

- Kubeadm: added the experimental (alpha) feature gate `EtcdLearnerMode` that allows etcd members to be joined as learner and only then promoted as voting members ([#113318](https://github.com/kubernetes/kubernetes/pull/113318), [@pacoxu](https://github.com/pacoxu))

[Setup topics]: https://kubernetes.io/docs/setup/pick-right-solution/
[SIGs]: https://github.com/kubernetes/community/blob/master/sig-list.md


## Major Themes

Kubernetes is developed by community members whose work is organized into
[Special Interest Groups][]. For the 1.8 release, each SIG provides the
themes that guided their work.

- Kubeadm: modify the etcd static Pod liveness and readyness probes to use a new etcd 3.5.3+ HTTP(s) health check endpoint "/health?serializable=true" that allows to track the health of individual etcd members and not fail all members if a single member is not healthy in the etcd cluster. ([#110072](https://github.com/kubernetes/kubernetes/pull/110072), [@neolit123](https://github.com/neolit123)) [SIG Cluster Lifecycle]

- Kubeadm: fix wrong member list reported when removing an etcd member ([#127962](https://github.com/kubernetes/kubernetes/pull/127962), [@SataQiu](https://github.com/SataQiu)) [SIG Cluster Lifecycle]

- Moved fluentd-elasticsearch addon images to community controlled location ([#73819](https://github.com/kubernetes/kubernetes/pull/73819), [@coffeepac](https://github.com/coffeepac))
- Removed local etcd members from the etcd cluster when `kubeadm reset` ([#74112](https://github.com/kubernetes/kubernetes/pull/74112), [@pytimer](https://github.com/pytimer))

* Upgrade to etcd client 3.3.17 to fix bug where etcd client does not parse IPv6 addresses correctly when members are joining, and to fix bug where failover on multi-member etcd cluster fails certificate check on DNS mismatch ([#83968](https://github.com/kubernetes/kubernetes/pull/83968), [@jpbetz](https://github.com/jpbetz))

* Add automatic etcd 3.2->3.1 and 3.1->3.0 minor version rollback support to gcr.io/google_container/etcd images. For HA clusters, all members must be stopped before performing a rollback. ([#59298](https://github.com/kubernetes/kubernetes/pull/59298), [@jpbetz](https://github.com/jpbetz))