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#set($dollar = '$')
#set($h1='#')
#set($h2='##')

$h1 Log4j Docker Support

Log4j supports Docker by providing a Lookup to retrieve container information.

$h2 Accessing Docker

The Log4j Docker support requires access to the Docker REST intrerface. In practical terms this means the
application either needs access to unix:///var/run/docker.sock through a volume mount (not recommended),
bind Docker to another host/port or unix socket. or use a proxy application to provide access. The
[Log4j Spring Cloud sample application](https://github.com/apache/logging-log4j2/tree/master/log4j-spring-cloud-config/log4j-spring-cloud-config-samples/log4j-spring-cloud-config-sample-application)
uses a socat proxy to access Docker.

$h2 Lookup Attributes

Log4j Docker provides access to the following container attributes:

* containerId - The full id assigned to the container.
* containerName - The name assigned to the container.
* imageId - The id assigned to the image.
* imageName - The name assigned to the image.
* shortContainerId - The first 12 characters of the container id.
* shortImageId - The first 12 characters of the image id.

#set( $D = '${' )
#set( $container = 'docker:containerId}')
Attributes may be accessed by adding
```
$D$container
```
to the configuration. Note that docker variables are only resolved once during logging initializaton so they
shouldn't be referenced with more than one '$' character.

$h2 Requirements
Log4j Docker requires Log4j Core, Log4j API and a minimum of Java 8.
For more information, see [Runtime Dependencies](../runtime-dependencies.html).
