Docker Image of the EPICS Archiver Appliance

This is the source repository for a Docker image containing the EPICS Archiver Appliance served by Apache Tomcat.
A pre-built image can be found on the Docker Hub at: /r/pklaus/archiver-appliance.

By the time of its creation, only a few Dockerfiles/ Docker deployments of the Archiver Appliance were published by controls scientists form around the world. Here's how this one differs / stands out:

• It uses a multi-stage build to pick (copy) only relevant assets from the Archiver Appliance release file.
• omits the typical installation scripts such as quickstart.sh / single_machine_install.sh,
• avoids puppet configuration management scripts, although a lot was learned from one of them,
• out of the box supports InMemoryPersistence and RedisPersistence (to use MySQL instead, its Connector/J .jar file would have to be added to the image),
• was also inspired by a Docker deployment by jsparger concerning the mounting of a local storage directory and the use of a docker-compose file (see example deployment below).

Example Deployment

This image may be deployed in many different ways depending on the network layout, need to reach other Docker containers on the same host etc.

A quick example of how to use it with an EPICS example IOC and a Redis db for persistence, check out pklaus / archiver-appliance-with-example-ioc.

For a production environment, it seems very favorable to run the container with --network=host in order to be reachable from the other machines on the network.

Guidelines for the Dockerfile

The Dockerfile for this image was written with the following aspects in mind:

• Attempt to be compact in size.
• Download the EPICS Archiver Appliance release in a first build stage and extract it.
• In the second build stage, start with a lightweight tomcat Docker image copy the unpacked Java web applications (.war files) from the first build stage to /usr/local/tomcat/webapps.
• Put any additional/modified/custom files in /etc/archappl/. If they are intended to replace other existing files of the software, those files are removed and a softlink to their replacement in /etc/archappl is created to make the customization transparent.
• Sane defaults for the environment variables are set in the Dockerfile, see the section below. Those environment variables can be adapted (overridden) on demand when deploying the container.

This way, the Dockerfile is very compact, the docker build context is small because downloading the release takes place inside the first build stage and in addition, the Dockerfile is very explicit about what parts of the release file are really needed to run the appliance.

Environment Variables Relevant for the EPICS Archiver Appliance

The Archiver Appliance has a set of various environment variables used to configure the appliance. Many of them can be found on the website, for example in the Installation Guide, the FAQ or the Javadoc documentation of the ConfigService class.

Some of them, however, are hard to find in the documents. As most of them start with ARCHAPPL_, I decided to search the Archiver Appliance source code for all of them. I ran grep -R ARCHAPPL_ . | grep -E -o 'ARCHAPPL_[A-Z0-9_]+' | sort | uniq inside a local copy of the source code. Here's the result:

ARCHAPPL_ALL_APPS_ON_ONE_JVM
ARCHAPPL_APPLIANCES
ARCHAPPL_COMPONENT
ARCHAPPL_CONFIGSERVICE_IMPL
ARCHAPPL_DEPLOY_DIR
ARCHAPPL_JDBM2_FILENAME
ARCHAPPL_LONG_TERM_FOLDER
ARCHAPPL_MEDIUM_TERM_FOLDER
ARCHAPPL_MYIDENTITY
ARCHAPPL_NAGIOS_EMAIL_CONFIG
ARCHAPPL_NAMEDFLAGS_PROPERTIES_FILE_PROPERTY
ARCHAPPL_PBRAW
ARCHAPPL_PERSISTENCE_LAYER
ARCHAPPL_PERSISTENCE_LAYER_JDBM2FILENAME
ARCHAPPL_PERSISTENCE_LAYER_REDISURL
ARCHAPPL_POLICIES
ARCHAPPL_PROPERTIES_FILENAME
ARCHAPPL_PVNAME_TO_KEY_MAPPING_CLASSNAME
ARCHAPPL_SHORT_TERM_FOLDER
ARCHAPPL_SITEID
ARCHAPPL_SRC

For their meaning, please refer to the sources cited. They are just stated here to serve as a reference. It has proven quite useful in many cases to check how they are used in the source code of the Archiver Appliance.