Introduction

Users can build their own Docker images for Agents.
This article explains options how to create the Agent image.

Dockerfile

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

Dockerfile for Agent Image

FROM openjdk:8-jre-alpine

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

# BUILD SETTINGS

# provide build arguments for release information
ARG JS_MAJOR
ARG JS_RELEASE

# default user id has to match later run-time user
ARG JS_USER_ID=${UID:-1001}
ARG JS_HTTP_PORT=${JS_HTTP_PORT:-4445}
ARG JS_HTTPS_PORT=${JS_HTTPS_PORT:-4443}
ARG JS_JAVA_OPTIONS=${JS_JAVA_OPTIONS}

# RUN-TIME SETTINGS

# JS7 JobScheduler ports and Java options
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 apk add --no-cache procps && \
    apk add --no-cache bash

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

# add installation tarball
ADD https://download.sos-berlin.com/Job
Scheduler.${JS_MAJOR}/js7_agent_unix.${JS_RELEASE}.tar.gz /usr/local/src/

# INSTALLATION

# extract 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_agent_unix.${JS_RELEASE}.tar.gz && \
    tar xfvz /usr/local/src/js7_agent_unix.${JS_RELEASE}.tar.gz -C /var/sos-berlin.com/js7  && \
    rm /usr/local/src/js7_agent_unix.${JS_RELEASE}.tar.gz && \
    sed -i 's/securerandom.source=file:\/dev\/random/securerandom.source=file:\/dev\/urandom/g' /usr/lib/jvm/java-1.8-openjdk/jre/lib/security/java.security

# CONFIGURATION

# copy configuration
COPY config/ /var/sos-berlin.com/js7/agent/var_$JS_HTTP_PORT/config/

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

# Alpine: make default user the owner of directories
RUN adduser -u ${JS_USER_ID:-1001} --disabled-password --home /home/jobscheduler --no-create-home --shell /bin/bash jobscheduler jobscheduler && \
    chown -R jobscheduler:jobscheduler /var/sos-berlin.com && \
    chmod +x /usr/local/bin/start-agent.sh

# CODA

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

# allow incoming traffic to port
EXPOSE $RUN_JS_HTTP_PORT $RUN_JS_HTTPS_PORT

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

Explanations:

Line 8 - 9: The release identification is injected by build arguments. This information is used to determine the tarball to be downloaded with line 35
Line 12 - 15: Defaults for the user id running the Agent inside the container as well as HTTP and HTTPS ports are provided. These values can be overwritten by providing the respective build arguments.
Line 20 - 22: 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 50: if a config folder is available in the build folder then its contents is copied to the respective config folder in the container. This can be used to create an image with updated configuration files, see JS7 - Agent Configuration Items.

Line 53: The start-agent.sh script is copied from the build folder to the container. Users can apply their own version of the start script. The start script used by SOS looks like this:

Agent Start Script

#!/bin/sh

js_http_port=""
js_https_port=""
js_java_options=""

for option in "$@"
do
  case "$option" in
         --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 Agent: /var/sos-berlin.com/js7/agent/bin/agent.sh start $js_args"
/var/sos-berlin.com/js7/agent/bin/agent.sh start $js_args && tail -f /dev/null

Line 56 - 58: The user account jobscheduler is created and is assigned the user id and group id handed over by the respective build argument. This translates to the fact that the account running the Agent 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 Agent in mounted volumes with identical permissions.
Line 66: The HTTP and optionally the HTTPS port that are forwarded by environment variables when running the container are exposed to the Docker host. This is relevant only if users wanted 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 68: 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:

Build Script for Agent Image

#!/bin/sh

set -e

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

IMAGE_NAME="$(basename "$SCRIPT_HOME")"
REPOSITORY_NAME="sosberlin/js7"


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

JS_MAJOR_DEFAULT="2.0"
JS_RELEASE_DEFAULT="2.0.0"

JS_USER_ID_DEFAULT="$UID"
JS_NETWORK_DEFAULT="js7"

JS_HTTP_PORT_DEFAULT="4445"
JS_HTTPS_PORT_DEFAULT="4443"

JS_JAVA_OPTIONS_DEFAULT="-Xmx500m"
JS_BUILD_ARGS_DEFAULT=""

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


for option in "$@"
do
  case "$option" in
         --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


JS_MAJOR="${JS_MAJOR:-$JS_MAJOR_DEFAULT}"
JS_RELEASE="${JS_RELEASE:-$JS_RELEASE_DEFAULT}"

JS_USER_ID="${JS_USER_ID:-$JS_USER_ID_DEFAULT}"
JS_NETWORK="${JS_NETWORK:-$JS_NETWORK_DEFAULT}"
JS_HTTP_PORT="${JS_HTTP_PORT:-$JS_HTTP_PORT_DEFAULT}"
JS_HTTPS_PORT="${JS_HTTPS_PORT:-$JS_HTTPS_PORT_DEFAULT}"
JS_JAVA_OPTIONS="${JS_JAVA_OPTIONS:-$JS_JAVA_OPTIONS_DEFAULT}"
JS_BUILD_ARGS="${JS_BUILD_ARGS:-$JS_BUILD_ARGS_DEFAULT}"

set -x

docker build --no-cache --rm \
      --tag=$REPOSITORY_NAME:$IMAGE_NAME \
      --file=$SCRIPT_HOME/build/Dockerfile \
      --network=$JS_NETWORK \
      --build-arg="JS_MAJOR=$JS_MAJOR" \
      --build-arg="JS_RELEASE=$JS_RELEASE" \
      --build-arg="JS_USER_ID=$JS_USER_ID" \
      --build-arg="JS_HTTP_PORT=$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:

TBD

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JS7 - Build Agent Docker Image

Introduction

Dockerfile

Build Script