Introduction

• Users can build their own Docker images for Controllers.
• This article explains options how to create the Controller image.

Build Environment

For the build environment the following directory hierarchy is assumed:

• js7-controller
  • build.sh
  • build
    • Dockerfile
    • start-controller.sh
    • config

The root directory js7-controller could have any name. Consider that below build script by default will use the directory name to determine the resulting image name.

The build script build.sh and Controller start script start-controller.sh are explained below.

Dockerfile

Docker images for JS7 Controllers provided by SOS make use of the following Dockerfile:

FROM openjdk:8-jre

LABEL maintainer="Software- und Organisations-Service GmbH"

# BUILD SETTINGS

# provide build arguments for release information
ARG JS_RELEASE
ARG JS_RELEASE_MAJOR

# default user id has to match later run-time user
ARG JS_USER_ID=${JS_USER_ID:-1001}
ARG JS_ID=${JS_ID:-jobscheduler}
ARG JS_HTTP_PORT=${JS_HTTP_PORT:-4444}
ARG JS_HTTPS_PORT=${JS_HTTPS_PORT:-4443}
ARG JS_JAVA_OPTIONS=${JS_JAVA_OPTIONS}

# RUN-TIME SETTINGS

# JS7 Controller ID, ports and Java options
ENV RUN_JS_ID=${RUN_JS_ID:-$JS_ID}
ENV RUN_JS_HTTP_PORT=${RUN_JS_HTTP_PORT:-$JS_HTTP_PORT}
ENV RUN_JS_HTTPS_PORT=${RUN_JS_HTTPS_PORT}
ENV RUN_JS_JAVA_OPTIONS=${RUN_JS_JAVA_OPTIONS:-$JS_JAVA_OPTIONS}

# PREPARATION

# install process tools, bash
RUN apt-get update && \
    apt-get install -y procps && \
    apt-get install -y bash

# setup working directory
RUN mkdir -p /var/sos-berlin.com/js7
WORKDIR /var/sos-berlin.com/js7

# add/copy installation tarball
ADD https://download.sos-berlin.com/JobScheduler.${JS_RELEASE_MAJOR}/js7_controller_unix.${JS_RELEASE}.tar.gz /usr/local/src/
# COPY js7_controller_unix.${JS_RELEASE}.tar.gz /usr/local/src/

# INSTALLATION

# extract installation tarball
#   for JDK < 12, /dev/random does not provide sufficient entropy, see https://kb.sos-berlin.com/x/lIM3
RUN test -e /usr/local/src/js7_controller_unix.${JS_RELEASE}.tar.gz && \
    tar xfvz /usr/local/src/js7_controller_unix.${JS_RELEASE}.tar.gz -C /var/sos-berlin.com/js7/ && \
    rm /usr/local/src/js7_controller_unix.${JS_RELEASE}.tar.gz && \
    sed -i 's/securerandom.source=file:\/dev\/random/securerandom.source=file:\/dev\/urandom/g' /usr/local/openjdk-8/lib/security/java.security

# CONFIGURATION

# copy configuration
COPY config/ /var/sos-berlin.com/js7/controller/var/config/

# add start script
COPY start-controller.sh  /usr/local/bin/

# add jobscheduler user account and make it the owner of directories
RUN groupadd --gid ${JS_USER_ID:-1001} jobscheduler && \
    useradd --uid ${JS_USER_ID:-1001} --gid jobscheduler --home-dir /home/jobscheduler --no-create-home --shell /bin/bash jobscheduler && \
    chown -R jobscheduler:jobscheduler /var/sos-berlin.com && \
    chmod +x /usr/local/bin/start-controller.sh

# CODA

# allow incoming traffic to ports
EXPOSE $RUN_JS_HTTP_PORT $RUN_JS_HTTPS_PORT

# run-time user, can be overwritten when running the container
USER jobscheduler

CMD ["sh","-c","/usr/local/bin/start-controller.sh --id=\"$RUN_JS_ID\" --http-port=$RUN_JS_HTTP_PORT --https-port=$RUN_JS_HTTPS_PORT --java-options=\"$RUN_JS_JAVA_OPTIONS\""]

Explanations:

• Line 1: The base image is OpenJDK Java 1.8 (Debian based). You can run Controllers with newer Java releases, however, stick to Oracle, OpenJDK or AdoptOpenJDK as the source for your Java base image. Alternatively you can use your own base image and install Java 1.8 on top of this.
• Line 8 - 9: The release identification is injected by build arguments. This information is used to determine the tarball to be downloaded.
• Line 12 - 16: Defaults for the Controller ID and user id running the Controller inside the container as well as HTTP and HTTPS ports are provided. These values can be overwritten by providing the respective build arguments.
• Line 21 - 24: Environment variables are provided at run-time, not at build-time. They can be used to specify ports and Java options when running the container.
• Line 38 - 39: You can either download the Controller tarball directly from the SOS web site or you store the tarball with the build directory and copy from this location.
• Line 53: if a config folder is available in the build directory then its contents is copied to the respective config folder in the container. This can be useful to create an image with individual settings in configuration files, see JS7 - Controller Configuration Items.

• Line 56: The start-controller.sh script is copied from the build directory to the container. Users can apply their own version of the start script. The start script used by SOS looks like this:

  Controller Start Script Expand source

  #!/bin/sh
  
  js_id=""
  js_http_port=""
  js_https_port=""
  js_java_options=""
  
  for option in "$@"
  do
    case "$option" in
           --id=*)           js_id=`echo "$option" | sed 's/--id=//'`
                             ;;
           --http-port=*)    js_http_port=`echo "$option" | sed 's/--http-port=//'`
                             ;;
           --https-port=*)   js_https_port=`echo "$option" | sed 's/--https-port=//'`
                             ;;
           --java-options=*) js_java_options=`echo "$option" | sed 's/--java-options=//'`
                             ;;
           *)                echo "unknown argument: $option"
                             exit 1
                             ;;
    esac
  done
  
  js_args=""
  
  if [ ! "$js_http_port" = "" ]
  then
    js_args="$js_args --http-port=$js_http_port"
  fi
  
  if [ ! "$js_https_port" = "" ]
  then
    js_args="$js_args --https-port=$js_https_port"
  fi
  
  if [ ! "$js_java_options" = "" ]
  then
    js_args="$js_args --java-options=$js_java_options"
  fi
  
  echo "starting Controller: /var/sos-berlin.com/js7/controller/bin/controller.sh start --id=$js_id $js_args"
  /var/sos-berlin.com/js7/controller/bin/controller.sh start --id=$js_id $js_args && tail -f /dev/null

• Line 59 - 62: The user account jobscheduler is created and is assigned the user id and group id handed over by the respective build arguments. This translates to the fact that the account running the Controller inside the container and the account that starts the container are assigned the same user id and group id. This allows the account running the container to access any files created by the Controller in mounted volumes with identical permissions.
• Line 69: The HTTP port and optionally the HTTPS port are exposed to the Docker host. Both ports can be forwarded by environment variables when running the container, overwriting the build-time values. This is relevant only if users want to use ports inside the container that are different from the default values. In most situations the default ports should be fine and are mapped to outside ports on the Docker host when starting the container.
• Line 72: The start script is executed and is dynamically parameterized from environment variables that are forwarded when starting the container.

Build Script

The build script offers a number of options to parameterize the Dockerfile:

#!/bin/sh

set -e

SCRIPT_HOME=$(dirname "$0")
SCRIPT_HOME="`cd "${SCRIPT_HOME}" >/dev/null && pwd`"
SCRIPT_FOLDER="`basename $(dirname "$SCRIPT_HOME")`"


# ----- modify default settings -----

JS_RELEASE="2.0.0-SNAPSHOT"
JS_REPOSITORY="sosberlin/js7"
JS_IMAGE="$(basename "${SCRIPT_HOME}")-${JS_RELEASE//\./-}"

JS_USER_ID="$UID"
JS_ID="jobscheduler"
JS_NETWORK="js7"

JS_HTTP_PORT="4444"
JS_HTTPS_PORT="4443"

JS_JAVA_OPTIONS="-Xmx500m"
JS_BUILD_ARGS=""

# ----- modify default settings -----


for option in "$@"
do
  case "$option" in
         --release=*)      JS_RELEASE=`echo "$option" | sed 's/--release=//'`
                           ;;
         --repository=*)   JS_REPOSITORY=`echo "$option" | sed 's/--repository=//'`
                           ;;
         --image=*)        JS_IMAGE=`echo "$option" | sed 's/--image=//'`
                           ;;
         --user-id=*)      JS_USER_ID=`echo "$option" | sed 's/--user-id=//'`
                           ;;
         --id=*)           JS_ID=`echo "$option" | sed 's/--id=//'`
                           ;;
         --network=*)      JS_NETWORK=`echo "$option" | sed 's/--network=//'`
                           ;;
         --http-port=*)    JS_HTTP_PORT=`echo "$option" | sed 's/--http-port=//'`
                           ;;
         --https-port=*)   JS_HTTPS_PORT=`echo "$option" | sed 's/--https-port=//'`
                           ;;
         --java-options=*) JS_JAVA_OPTIONS=`echo "$option" | sed 's/--java-options=//'`
                           ;;
         --build-args=*)   JS_BUILD_ARGS=`echo "$option" | sed 's/--build-args=//'`
                           ;;
         *)                echo "unknown argument: $option"
                           exit 1
                           ;;
  esac
done

set -x

docker build --no-cache --rm \
      --tag=$JS_REPOSITORY:$JS_IMAGE \
      --file=$SCRIPT_HOME/build/Dockerfile \
      --network=$JS_NETWORK \
      --build-arg="JS_RELEASE=$JS_RELEASE" \
      --build-arg="JS_RELEASE_MAJOR=$(echo $JS_RELEASE | cut -d . -f 1,2)" \
      --build-arg="JS_USER_ID=$JS_USER_ID" \
      --build-arg="JS_ID=$JS_ID" \
      --build-arg="JS_HTTP_PORT=$JS_HTTP_PORT" \
      --build-arg="JS_HTTPS_PORT=$JS_HTTPS_PORT" \
      --build-arg="JS_JAVA_OPTIONS=$JS_JAVA_OPTIONS" \
      $JS_BUILD_ARGS $SCRIPT_HOME/build

set +x

Explanations:

• Line 12 - 24: Default values are specified that are used if no command line arguments are provided. This includes values for
  • the release number: adjust this value to a current release of JS7.
  • the repository which by default is sosberlin:js7.
  • the image name is determined from the current folder name and the release number.
  • the user id by default is the user id of the user running the build script.
  • the Controller ID can be specified that is a unique identifier for a Controller installation.
  • the Docker network: the build script assumes a Docker network to be used for which a name is specified.
  • the HTTP port and HTTPS port: if the respective port is not specified then the Controller will not listen to a port for the respective protocol. You can for example disable the HTTP protocol by specifying an empty value. The default ports should be fine as they are mapped by the run script to outside ports on the Docker host. However, you can modify ports as you like.
  • Java options: typically you would specify default values e.g. for Java memory consumption. The Java options can be overwritten by the run script when starting the container, however, you might want to create your own image with adjusted default values.
• Line 29 - 56: The above options can be overwritten by command line arguments like this:

  
  

  Running the Build Script with Arguments

  ./build.sh --id=js7-prod --network=js --http-port=14445 --https-port=14443 --java-options="-Xmx1G"

• Line 60 - 71: The effective docker build command is executed with arguments. The Dockerfile is assumed to be located with the build sub-directory of the current directory.