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Add docs for settings via env vars on Docker (#7015)

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Toby McLaughlin 2017-05-04 15:21:44 +10:00 • committed by Suyog Rao
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commit a76375d094
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docs/static/docker.asciidoc vendored
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@ -3,8 +3,16 @@
Docker images for Logstash are available from the Elastic Docker
registry.
Obtaining Logstash for Docker is as simple as issuing a +docker pull+
command against the Elastic Docker registry.
The base image is https://hub.docker.com/_/centos/[centos:7] and the source
code can be found on
https://github.com/elastic/logstash-docker/tree/{branch}[GitHub].
The images are shipped with https://www.elastic.co/products/x-pack[X-Pack]
installed.
=== Pulling the image
Obtaining Logstash for Docker is as simple as issuing a +docker
pull+ command against the Elastic Docker registry.
ifeval::["{release-state}"=="unreleased"]
@ -69,7 +77,14 @@ behaviour that you are observing, ensure that your pipeline
configuration is being picked up correctly, and that you are replacing
either +logstash.conf+ or the entire +pipeline+ directory.
===== Settings Files
===== Settings
The image provides several methods for configuring settings. The conventional
approach is to provide a custom `logstash.yml` file, but it's
also possible to use environment variables to define settings.
[[docker-bind-mount-settings]]
==== Bind-mounted settings files
Settings files can also be provided through bind-mounts. Logstash
expects to find them at +/usr/share/logstash/config/+.
@ -112,6 +127,35 @@ ADD config/ /usr/share/logstash/config/
Be sure to replace or delete `logstash.conf` in your custom image, so
that you don't retain the example config from the base image.
==== Environment variable configuration
Under Docker, Logstash settings can be configured via environment
variables. When the container starts, a helper process checks the environment
for variables that can be mapped to Logstash settings. Settings that are found
in the environment are merged into `logstash.yml` as the container starts up.
For compatibility with container orchestration systems, these environment
variables are written in all capitals, with underscores as word
separators
Some example translations are shown here:
.Example Docker Environment Variables
[horizontal]
**Environment Variable**:: **Logstash Setting**
`PIPELINE_WORKERS`:: `pipeline.workers`
`LOG_LEVEL`:: `log.level`
`XPACK_MONITORING_ENABLED`:: `xpack.monitoring.enabled`
In general, any setting listed in the <<logstash-settings-file, settings
documentation>> can be configured with this technique.
NOTE: Defining settings with environment variables causes `logstash.yml` to
be modified in place. This behaviour is likely undesirable if `logstash.yml` was
bind-mounted from the host system. Thus, it is not reccomended to
combine the bind-mount technique with the environment variable technique. It
is best to choose a single method for defining Logstash settings.
==== Logging Configuration
Under Docker, Logstash logs go to standard output by default. To