Log4j Kubernetes Support

Accessing Kubernetes

The Log4j Kubernetes support requires access to the Docker REST interface. In many cases the REST service can be accessed automatically. If needed the Kubernetes client can be configured any of the standard Log4j configuration locations or via the Spring Boot configuration. Note, however, that since Spring Boot causes logging to initialize 3 times and since the Spring environment is only available during the last Log4j initialization Spring properties will only be available to Log4j in the last initialization.

Lookup Attributes

Log4j Kubernetes provides access to the following container attributes:

• accountName - The service account name.
• clusterName - The name of the cluster the application is running in.
• containerId - The full id assigned to the container.
• containerName - The name assigned to the container.
• host - The name of the host.
• hostIp - The host’s ip address.
• imageId - The id assigned to the image.
• imageName - The name assigned to the image.
• labels - All labels formatted in a list.
• labels.app - The application name.
• labels.podTemplateHash - The pod’s template hash value.
• masterUrl - The url needed to access the API server.
• namespaceId - The id of the namespace the various kubernetes components are located within.
• namespaceName - The namespace the various kubernetes components are located within.
• podId - The pod’s id number.
• podIp - The pod’s ip address.
• podName - The name of the pod.

Attributes may be accessed by adding

${k8s:containerId}

to the configuration. Note that kubernetes variables are only resolved once during logging initialization so they shouldn’t be referenced with more than one ‘$’ character.

Configuration

Much of the configuration needed to access the Kubernetes API server is provided automatically by Kubernetes. However, it is not uncommon to need to provide the url required to access the Kubernetes API server or the namespace the application is assigned to. The properties below may either be configured using the Log4j variable names and located by Log4j’s normal property resolution mechansim or Log4j will resolve the spring properties when the application is running in Spring Boot and the Spring Environment has been created. Note that Spring Boot initializes logging 3 times and only the last will have a Spring Environment present.

Requirements

Log4j Kubernetes requires Log4j Core, Log4j API and a minimum of Java 8. For more information, see Runtime Dependencies.