Closes#43990. Describe how to change the default GC settings without changing
the default `jvm.options`. Give examples using `jvm.options.d`, and
`ES_JAVA_OPTS` with Docker.
This commit introduces the ability to override JVM options by adding
custom JVM options files to a jvm.options.d directory. This simplifies
administration of Elasticsearch by not requiring administrators to keep
the root jvm.options file in sync with changes that we make to the root
jvm.options file. Instead, they are not expected to modify this file but
instead supply their own in jvm.options.d. In Docker installations, this
means they can bind mount this directory in. In future versions of
Elasticsearch, we can consider removing the root jvm.options file
(instead, providing all options there as system JVM options).
Backport of #51867.
Tweak the documentation around configuring the heap size when using
Docker, to state that:
- using `ES_JAVA_OPTS` is the preferred method
- Any `ES_JAVA_OPTS` overrides the defaults in `jvm.options`
- It's possible to bind-mount a custom `jvm.options`
This commit reorganizes some of the content in the configuring
Elasticsearch section of the docs. The changes are:
- move JVM options out of system configuration into configuring
Elasticsearch
- move JVM options to its own page of the docs
- move configuring the heap to important Elasticsearch settings
- move configuring the heap to its own page of the docs
- move all important settings to individual pages in the docs
- remove bootstrap.memory_lock from important settings, this is covered
in the swap section of system configuration
Relates #27755
Rory Hunter
Jason Tedor