There are two different Open Liberty Docker image sets available on Docker Hub:

1. Supported Images

   • Our recommended set here. These are images using Red Hat's Universal Base Image as the Operating System and are re-built daily.
   • Other sets can be found here. These are re-built automatically anytime something changes in the layers below. There are tags with different combinations of Java and Operating System versions.

2. Daily Images

   • Available here, these are daily images from the daily Open Liberty binaries. The scripts used for this image can be found here.

According to Docker's best practices you should create a new image (FROM open-liberty) which adds a single application and the corresponding configuration. You should avoid configuring the image manually, after it started (unless it is for debugging purposes), because such changes won't be present if you spawn a new container from the image.

Even if you docker save the manually configured container, the steps to reproduce the image from open-liberty will be lost and you will hinder your ability to update that image.

The key point to take-away from the sections below is that your application Dockerfile should always follow a pattern similar to:

FROM open-liberty:kernel

# Add my app and config
COPY --chown=1001:0  Sample1.war /config/dropins/
COPY --chown=1001:0  server.xml /config/

# Default setting for the verbose option
ARG VERBOSE=false

# Optional functionality
ARG SSL=true
ARG MP_MONITORING=true

# This script will add the requested XML snippets and grow image to be fit-for-purpose
RUN configure.sh

This will result in a Docker image that has your application and configuration pre-loaded, which means you can spawn new fully-configured containers at any time.

This section describes the optional enterprise functionality that can be enabled via the Dockerfile during build time, by setting particular build-arguments (ARG) and calling RUN configure.sh. Each of these options trigger the inclusion of specific configuration via XML snippets (except for VERBOSE), described below:

• HTTP_ENDPOINT
  • Decription: Add configuration properties for an HTTP endpoint.
  • XML Snippet Location: http-ssl-endpoint.xml when SSL is enabled. Otherwise http-endpoint.xml
• MP_HEALTH_CHECK
  • Decription: Check the health of the environment using Liberty feature mpHealth-1.0 (implements MicroProfile Health).
  • XML Snippet Location: mp-health-check.xml
• MP_MONITORING
  • Decription: Monitor the server runtime environment and application metrics by using Liberty features mpMetrics-1.1 (implements Microprofile Metrics) and monitor-1.0.
  • XML Snippet Location: mp-monitoring.xml
  • Note: With this option, /metrics endpoint is configured without authentication to support the environments that do not yet support scraping secured endpoints.
• TLS or SSL (SSL is being deprecated)
  • Decription: Enable Transport Security in Liberty by adding the transportSecurity-1.0 feature (includes support for SSL).
  • XML Snippet Location: keystore.xml.
• IIOP_ENDPOINT
  • Decription: Add configuration properties for an IIOP endpoint.
  • XML Snippet Location: iiop-ssl-endpoint.xml when SSL is enabled. Otherwise, iiop-endpoint.xml.
  • Note: If using this option, env.IIOP_ENDPOINT_HOST environment variable should be set to the server's host. See IIOP endpoint configuration for more details.
• JMS_ENDPOINT
  • Decription: Add configuration properties for an JMS endpoint.
  • XML Snippet Location: jms-ssl-endpoint.xml when SSL is enabled. Otherwise, jms-endpoint.xml
• VERBOSE
  • Description: When set to true it outputs the commands and results to stdout from configure.sh. Otherwise, default setting is false and configure.sh is silenced.

OpenJ9's SCC allows the VM to store Java classes in an optimized form that can be loaded very quickly, JIT compiled code, and profiling data. Deploying an SCC file together with your application can significantly improve start-up time. The SCC can also be shared by multiple VMs, thereby reducing total memory consumption.

Open Liberty Docker images contain an SCC and (by default) add your application's specific data to the SCC at image build time when your Dockerfile invokes RUN configure.sh.

This feature can be controlled via the following variables:

• OPENJ9_SCC (environment variable)
  • Decription: If "true", cache application-specific in an SCC and include it in the image. A new SCC will be created if needed, otherwise data will be added to the existing SCC.
  • Default: "true".

To customize one of the built-in XML snippets, make a copy of the snippet from Github and edit it locally. Once you have completed your changes, use the COPY command inside your Dockerfile to copy the snippet into /config/configDropins/overrides. It is important to note that you do not need to set build-arguments (ARG) for any customized XML snippets. The following Dockerfile snippet is an example of how you should include the customized snippet.

COPY --chown=1001:0 <path_to_customized_snippet> /config/configDropins/overrides

It is important to be able to observe the logs emitted by Open Liberty when it is running in docker. A best practice method would be to emit the logs in JSON and to then consume it with a logging stack of your choice.

Configure your Open Liberty docker image to emit JSON formatted logs to the console/standard-out with your selection of liberty logging events by creating a bootstrap.properties file with the following properties. You can also disable writing to the messages.log or trace.log files if you don't need them.

# direct events to console in json format
com.ibm.ws.logging.console.log.level=info
com.ibm.ws.logging.console.format=json
com.ibm.ws.logging.console.source=message,trace,accessLog,ffdc,audit

# disable writing to messages.log by not including any sources (optional)
com.ibm.ws.logging.message.format=json
com.ibm.ws.logging.message.source=

# disable writing to trace.log by only sending trace data to console (optional)
com.ibm.ws.logging.trace.file.name=stdout

Make sure to include the file you have just created into your Open Liberty Dockerfile.

COPY --chown=1001:0  bootstrap.properties /config/

Many of these configuration changes can also be set during container invocation by using the Docker command's '-e' option to pass in an environment variable value.

docker run -d -p 80:9080 -p 443:9443 -e WLP_LOGGING_CONSOLE_FORMAT=JSON -e WLP_LOGGING_CONSOLE_LOGLEVEL=info -e WLP_LOGGING_CONSOLE_SOURCE=message,trace,accessLog,ffdc,audit open-liberty:latest

For more information regarding the configuration of Open Liberty's logging capabilities see: https://openliberty.io/docs/ref/general/#logging.html

The Liberty session caching feature builds on top of an existing technology called JCache (JSR 107), which provides an API for distributed in-memory caching. There are several providers of JCache implementations. One example is Hazelcast In-Memory Data Grid. Enabling Hazelcast session caching retrieves the Hazelcast client libraries from the hazelcast/hazelcast Docker image, configures Hazelcast by copying a sample hazelcast.xml, and configures the Liberty server feature sessionCache-1.0 by including the XML snippet hazelcast-sessioncache.xml. By default, the Hazelcast Discovery Plugin for Kubernetes will auto-discover its peers within the same Kubernetes namespace. To enable this functionality, the Docker image author can include the following Dockerfile snippet, and choose from either client-server or embedded topology.

### Hazelcast Session Caching ###
# Copy the Hazelcast libraries from the Hazelcast Docker image
COPY --from=hazelcast/hazelcast --chown=1001:0 /opt/hazelcast/lib/*.jar /opt/ol/wlp/usr/shared/resources/hazelcast/

# Instruct configure.sh to copy the client topology hazelcast.xml
ARG HZ_SESSION_CACHE=client

# Default setting for the verbose option
ARG VERBOSE=false

# Instruct configure.sh to copy the embedded topology hazelcast.xml and set the required system property
#ARG HZ_SESSION_CACHE=embedded
#ENV JAVA_TOOL_OPTIONS="-Dhazelcast.jcache.provider.type=server ${JAVA_TOOL_OPTIONS}"

## This script will add the requested XML snippets and grow image to be fit-for-purpose
RUN configure.sh