110 lines
3.9 KiB
Plaintext
110 lines
3.9 KiB
Plaintext
[[setup-configuration-memory]]
|
|
=== Disable swapping
|
|
|
|
Most operating systems try to use as much memory as possible for file system
|
|
caches and eagerly swap out unused application memory. This can result in parts
|
|
of the JVM heap or even its executable pages being swapped out to disk.
|
|
|
|
Swapping is very bad for performance, for node stability, and should be avoided
|
|
at all costs. It can cause garbage collections to last for **minutes** instead
|
|
of milliseconds and can cause nodes to respond slowly or even to disconnect
|
|
from the cluster. In a resilient distributed system, it's more effective to let
|
|
the operating system kill the node.
|
|
|
|
There are three approaches to disabling swapping. The preferred option is to
|
|
completely disable swap. If this is not an option, whether or not to prefer
|
|
minimizing swappiness versus memory locking is dependent on your environment.
|
|
|
|
[[disable-swap-files]]
|
|
==== Disable all swap files
|
|
|
|
Usually Elasticsearch is the only service running on a box, and its memory usage
|
|
is controlled by the JVM options. There should be no need to have swap enabled.
|
|
|
|
On Linux systems, you can disable swap temporarily by running:
|
|
|
|
[source,sh]
|
|
--------------
|
|
sudo swapoff -a
|
|
--------------
|
|
|
|
To disable it permanently, you will need to edit the `/etc/fstab` file and
|
|
comment out any lines that contain the word `swap`.
|
|
|
|
On Windows, the equivalent can be achieved by disabling the paging file entirely
|
|
via `System Properties → Advanced → Performance → Advanced → Virtual memory`.
|
|
|
|
[[swappiness]]
|
|
==== Configure `swappiness`
|
|
|
|
Another option available on Linux systems is to ensure that the sysctl value
|
|
`vm.swappiness` is set to `1`. This reduces the kernel's tendency to swap and
|
|
should not lead to swapping under normal circumstances, while still allowing the
|
|
whole system to swap in emergency conditions.
|
|
|
|
[[bootstrap-memory_lock]]
|
|
==== Enable `bootstrap.memory_lock`
|
|
|
|
Another option is to use
|
|
http://opengroup.org/onlinepubs/007908799/xsh/mlockall.html[mlockall] on
|
|
Linux/Unix systems, or
|
|
https://msdn.microsoft.com/en-us/library/windows/desktop/aa366895%28v=vs.85%29.aspx[VirtualLock]
|
|
on Windows, to try to lock the process address space into RAM, preventing any
|
|
Elasticsearch memory from being swapped out. This can be done, by adding this
|
|
line to the `config/elasticsearch.yml` file:
|
|
|
|
[source,yaml]
|
|
--------------
|
|
bootstrap.memory_lock: true
|
|
--------------
|
|
|
|
WARNING: `mlockall` might cause the JVM or shell session to exit if it tries to
|
|
allocate more memory than is available!
|
|
|
|
After starting Elasticsearch, you can see whether this setting was applied
|
|
successfully by checking the value of `mlockall` in the output from this
|
|
request:
|
|
|
|
[source,js]
|
|
--------------
|
|
GET _nodes?filter_path=**.mlockall
|
|
--------------
|
|
// CONSOLE
|
|
|
|
If you see that `mlockall` is `false`, then it means that the `mlockall`
|
|
request has failed. You will also see a line with more information in the logs
|
|
with the words `Unable to lock JVM Memory`.
|
|
|
|
The most probable reason, on Linux/Unix systems, is that the user running
|
|
Elasticsearch doesn't have permission to lock memory. This can be granted as
|
|
follows:
|
|
|
|
`.zip` and `.tar.gz`::
|
|
|
|
Set <<ulimit,`ulimit -l unlimited`>> as root before starting Elasticsearch,
|
|
or set `memlock` to `unlimited` in
|
|
<<limits.conf,`/etc/security/limits.conf`>>.
|
|
|
|
RPM and Debian::
|
|
|
|
Set `MAX_LOCKED_MEMORY` to `unlimited` in the
|
|
<<sysconfig,system configuration file>> (or see below for systems using
|
|
`systemd`).
|
|
|
|
Systems using `systemd`::
|
|
|
|
Set `LimitMEMLOCK` to `infinity` in the <<systemd,systemd configuration>>.
|
|
|
|
Another possible reason why `mlockall` can fail is that
|
|
<<executable-jna-tmpdir,the JNA temporary directory (usually a sub-directory of
|
|
`/tmp`) is mounted with the `noexec` option>>. This can be solved by specifying
|
|
a new temporary directory for JNA using the `ES_JAVA_OPTS` environment variable:
|
|
|
|
[source,sh]
|
|
--------------
|
|
export ES_JAVA_OPTS="$ES_JAVA_OPTS -Djna.tmpdir=<path>"
|
|
./bin/elasticsearch
|
|
--------------
|
|
|
|
or setting this JVM flag in the jvm.options configuration file.
|