Elasticsearch provides native scripting (that is, Java code compiled in JAR) and Painless, but a lot of other interesting languages are also available, such as Kotlin.
At the time of writing this book, there are no available language plugins as part of Elasticsearch's official ones. Usually, plugin authors will take up to a week or a month to update their plugins to the new version after a major release.
As previously stated, the official language is now Painless, and this is provided by default in Elasticsearch for better sandboxing and performance.
