With this commit we specify `level` in JVM logs. `level` helps to filter
more severe messages from mere debugging messages in logs and with this
change we are able to use it also for JVM logs.
Here are a few example lines:
Before:
```
[2022-12-15T06:19:16.936+0000][15181][gc,start ] GC(0) Pause Young (Normal) (G1 Evacuation Pause)
```
After:
```
[2022-12-15T06:22:27.932+0000][16320][info][gc,start ] GC(0) Pause Young (Normal) (G1 Evacuation Pause)
[2022-12-15T06:22:27.932+0000][16320][debug][gc,age ] GC(0) Desired survivor size 14680064 bytes, new threshold 15 (max threshold 15)
[2022-12-15T06:22:27.935+0000][16320][info ][gc,phases ] GC(0) Pre Evacuate Collection Set: 0.1ms
[2022-12-15T06:22:27.935+0000][16320][trace][gc,age ] GC(0) Age table with threshold 15 (max threshold 15)
```
Notice, that the log level might have trailing spaces.
See also
https://docs.oracle.com/en/java/javase/19/docs/specs/man/java.html#xlog-tags-and-levels
for the available log levels.
ES_JAVA_OPTS is still the correct way to pass options to
the Elasticsearch process, CLI_JAVA_OPTS affects only the
command line tool. CLI_JAVA_OPTS is the correct way to pass
options for plugin installation or other tools.
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 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
