[[release-notes-8.0.0-rc2]]
== {es} version 8.0.0-rc2

Also see <<breaking-changes-8.0,Breaking changes in 8.0>>.

[[known-issues-8.0.0-rc2]]
[float]
=== Known issues

* **Do not upgrade production clusters to {es} 8.0.0-rc2.** {es} 8.0.0-rc2 is
a pre-release of {es} 8.0 and is intended for testing purposes only.
+
Upgrades from pre-release builds are not supported and could result in errors or
data loss. If you upgrade from a released version, such as 7.16, to a
pre-release version for testing, discard the contents of the cluster when you are
done. Do not attempt to upgrade to the final 8.0 release.

* If you installed {es} from an archive on an aarch64 platform like Linux ARM or macOS M1, the
`elastic` user password and {kib} enrollment token are not generated
automatically when starting your node for the first time.
+
--
After the node starts, generate the `elastic` password with the
<<reset-password,`bin/elasticsearch-reset-password`>> tool:

[source,bash]
----
bin/elasticsearch-reset-password -u elastic
----

Then, create an enrollment token for {kib} with the
<<create-enrollment-token,`bin/elasticsearch-create-enrollment-token`>> tool:

[source,bash]
----
bin/elasticsearch-create-enrollment-token -s kibana
----
--
[[deprecation-8.0.0-rc2]]
[float]
=== Deprecations

Engine::
* Deprecate setting `max_merge_at_once_explicit` {es-pull}80574[#80574]

Search::
* Configure `IndexSearcher.maxClauseCount()` based on node characteristics {es-pull}81525[#81525] (issue: {es-issue}46433[#46433])


[[feature-8.0.0-rc2]]
[float]
=== New features

Snapshot/Restore::
* Support IAM roles for Kubernetes service accounts {es-pull}81255[#81255] (issue: {es-issue}52625[#52625])

Watcher::
* Use `startsWith` rather than exact matches for Watcher history template names {es-pull}82396[#82396]


[[enhancement-8.0.0-rc2]]
[float]
=== Enhancements

Cluster Coordination::
* Make `TaskBatcher` less lock-heavy {es-pull}82227[#82227] (issue: {es-issue}77466[#77466])

ILM+SLM::
* Avoid unnecessary `LifecycleExecutionState` recalculation {es-pull}81558[#81558] (issues: {es-issue}77466[#77466], {es-issue}79692[#79692])
* Make unchanged ILM policy updates into no-op {es-pull}82240[#82240] (issue: {es-issue}82065[#82065])

Infra/Core::
* Prevent upgrades to 8.0 without first upgrading to the last 7.x release {es-pull}82321[#82321] (issue: {es-issue}81865[#81865])

Machine Learning::
* Add `deployment_stats` to trained model stats {es-pull}80531[#80531]
* The setting `use_auto_machine_memory_percent` now defaults to `max_model_memory_limit` {es-pull}80532[#80532] (issue: {es-issue}80415[#80415])

Network::
* Improve slow inbound handling to include response type {es-pull}80425[#80425]

Packaging::
* Convert repository plugins to modules {es-pull}81870[#81870] (issue: {es-issue}81652[#81652])

Search::
* Check nested fields earlier in kNN search {es-pull}80516[#80516] (issue: {es-issue}78473[#78473])


[[bug-8.0.0-rc2]]
[float]
=== Bug fixes

Autoscaling::
* Use adjusted total memory instead of total memory {es-pull}80528[#80528] (issue: {es-issue}78750[#78750])

Infra/Scripting::
* Fix duplicated allow lists upon script engine creation {es-pull}82820[#82820] (issue: {es-issue}82778[#82778])

Ingest::
* Adjust default geoip logging to be less verbose {es-pull}81404[#81404] (issue: {es-issue}81356[#81356])

Machine Learning::
* Check that `total_definition_length` is consistent before starting a deployment {es-pull}80553[#80553]
* Fail inference processor more consistently on certain error types {es-pull}81475[#81475]
* Optimize the job stats call to do fewer searches {es-pull}82362[#82362] (issue: {es-issue}82255[#82255])

Recovery::
* Make shard started response handling only return after the cluster state update completes {es-pull}82790[#82790] (issue: {es-issue}81628[#81628])

Search::
* Reject zero-length vectors when using cosine similarity {es-pull}82241[#82241] (issue: {es-issue}81167[#81167])

Security::
* Auto-generated TLS files under fixed config path {es-pull}81547[#81547] (issue: {es-issue}81057[#81057])
* Bind to non-localhost for transport in some cases {es-pull}82973[#82973]
* Correct file ownership on node reconfiguration {es-pull}82789[#82789] (issue: {es-issue}80990[#80990])
* Display security auto-configuration with fancy unicode {es-pull}82740[#82740] (issue: {es-issue}82364[#82364])

Snapshot/Restore::
* Remove custom metadata if there is nothing to restore {es-pull}81373[#81373] (issues: {es-issue}81247[#81247], {es-issue}82019[#82019])


[[upgrade-8.0.0-rc2]]
[float]
=== Upgrades

Infra/Logging::
* Upgrade ECS logging layout to latest version {es-pull}80500[#80500]

Search::
* Upgrade to released lucene 9.0.0 {es-pull}81426[#81426]
