Introduction

This article describes a simplified build process for Agent images which is extracted from the SOS build environment.
Users can build their own container images for Agents.

Build Environment

The following directory hierarchy is assumed for the build environment:

agent
- build.sh
- build
  - Dockerfile
  - entrypoint.sh
  - config

The root directory agent can have any name. Note that build script listed below will, by default, use the directory name and release number to determine the resulting image name.

The build script build.sh and entrypoint script entrypoint.sh are described below.

Dockerfile

Download: Dockerfile

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

Dockerfile for Agent Image

# BUILD PRE-IMAGE

FROM alpine:3.15 AS js7-pre-image

# provide build arguments for release information
ARG JS_RELEASE
ARG JS_RELEASE_MAJOR
ARG JS_HTTP_PORT=${JS_HTTP_PORT:-4445}

# add/copy tarball
# ADD https://download.sos-berlin.com/JobScheduler.${JS_RELEASE_MAJOR}/js7_agent_unix.${JS_RELEASE}.tar.gz /usr/local/src/
COPY js7_agent_unix.${JS_RELEASE}.tar.gz /usr/local/src/

RUN mkdir -p /var/sos-berlin.com/js7 && \
    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

# add entrypoint script
COPY entrypoint.sh /var/sos-berlin.com/js7/

# copy default configuration
COPY config/ /var/sos-berlin.com/js7/agent/var_build/config/

# BUILD IMAGE

FROM alpine:3.15 AS js7-image

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

# 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=${UID:-1001}
ARG JS_HTTP_PORT=${JS_HTTP_PORT:-4445}
ARG JS_HTTPS_PORT=${JS_HTTPS_PORT:-""}
ARG JS_JAVA_OPTIONS=${JS_JAVA_OPTIONS}

# JS7 JobScheduler user id, ports and Java options
ENV RUN_JS_USER_ID=${RUN_JS_USER_ID:-1001}
ENV RUN_JS_HTTP_PORT=${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}

COPY --from=js7-pre-image ["/var/sos-berlin.com/js7", "/var/sos-berlin.com/js7"]

# INSTALLATION

# install process tools, net tools, bash, openjdk
# for JDK < 12, /dev/random does not provide sufficient entropy, see https://kb.sos-berlin.com/x/lIM3
# make default user the owner of directories
RUN apk update && apk add --no-cache \
    --repository=http://dl-cdn.alpinelinux.org/alpine/edge/community \
    procps \
    net-tools \
    su-exec \
    bash \
    shadow \
    openjdk11 && \
    sed -i 's/securerandom.source=file:\/dev\/random/securerandom.source=file:\/dev\/urandom/g' /usr/lib/jvm/java-11-openjdk/conf/security/java.security && \
    sed -i 's/jdk.tls.disabledAlgorithms=SSLv3, RC4, DES, MD5withRSA, DH keySize < 1024, \\/jdk.tls.disabledAlgorithms=SSLv3, RC4, DES, MD5withRSA, DH keySize < 1024, TLSv1, TLSv1.1, \\/g' /usr/lib/jvm/java-11-openjdk/conf/security/java.security && \
    adduser -u ${JS_USER_ID:-1001} --disabled-password --home /home/jobscheduler --shell /bin/bash jobscheduler jobscheduler && \
    chown -R jobscheduler:jobscheduler /var/sos-berlin.com && \
    mv /var/sos-berlin.com/js7/entrypoint.sh /usr/local/bin/ && \
    chmod +x /usr/local/bin/entrypoint.sh && \
    mv /var/sos-berlin.com/js7/agent/var_build /var/sos-berlin.com/js7/agent/var_$(echo $JS_HTTP_PORT | cut -d : -f 2)

# START

ENTRYPOINT ["/usr/local/bin/entrypoint.sh"]

CMD ["/var/sos-berlin.com/js7/agent/bin/agent.sh","start_docker"]

Explanation:

The build script implements two stages to exclude installer files from the resulting image.
Line 3: The base image is the current Alpine image at build-time.
Line 6 - 8: The release identification is injected by build arguments. This information is used to determine the tarball to be downloaded or copied.
Line 11 - 12: You can either download the Agent tarball directly from the SOS web site or you store the tarball with the build directory and copy from this location.
Line 14 - 16: The tarball is extracted. For Unix Agents no installer is used.

Line 19: The entrypoint.sh script is copied from the build directory to the image. Users can apply their own version of the entrypoint script. The entrypoint script used by SOS looks like this:
Download: entrypoint.sh

Entrypoint Script

#!/bin/bash

js_args=()
js_args_count=0

if [ ! "$RUN_JS_HTTP_PORT" = "" ] && [ ! "$RUN_JS_HTTP_PORT" = ":" ]
then
  js_http_port=$RUN_JS_HTTP_PORT
  js_args[$js_args_count]="--http-port=$RUN_JS_HTTP_PORT"
  js_args_count=$(( $js_args_count + 1 ))
else
  js_http_port=4445
fi

if [ ! "$RUN_JS_HTTPS_PORT" = "" ] && [ ! "$RUN_JS_HTTPS_PORT" = ":" ]
then
  js_args[$js_args_count]="--https-port=$RUN_JS_HTTPS_PORT"
  js_args_count=$(( $js_args_count + 1 ))
fi

if [ ! "$RUN_JS_JAVA_OPTIONS" = "" ]
then
  js_args[$js_args_count]="--java-options=\"$RUN_JS_JAVA_OPTIONS\""
  js_args_count=$(( $js_args_count + 1 ))
fi

if [ ! "$RUN_JS_JOB_JAVA_OPTIONS" = "" ]
then
  js_args[$js_args_count]="--job-java-options=\"$RUN_JS_JOB_JAVA_OPTIONS\""
  js_args_count=$(( $js_args_count + 1 ))
fi

# work directory is created by container
if [ -d "/var/sos-berlin.com/js7/agent/var_$js_http_port/work"  ]
then
  rm -fr /var/sos-berlin.com/js7/agent/var_$js_http_port/work
fi

JS_USER_ID=`echo $RUN_JS_USER_ID | cut -d ':' -f 1`
JS_GROUP_ID=`echo $RUN_JS_USER_ID | cut -d ':' -f 2`

BUILD_GROUP_ID=`cat /etc/group | grep jobscheduler | cut -d ':' -f 3`
BUILD_USER_ID=`cat /etc/passwd | grep jobscheduler | cut -d ':' -f 4`

if [ "$(id -u)" = "0" ]
then
  if [ ! "$BUILD_USER_ID" = "$JS_USER_ID" ]
  then
    echo "JS7 entrypoint script switchng ownership of image user id '$BUILD_USER_ID' -> '$JS_USER_ID', group id '$BUILD_GROUP_ID' -> '$JS_GROUP_ID'"
    usermod -u $JS_USER_ID jobscheduler
    groupmod -g $JS_GROUP_ID jobscheduler
    find /var/sos-berlin.com/ -group $BUILD_GROUP_ID -exec chgrp -h jobscheduler {} \;
    find /var/sos-berlin.com/ -user $BUILD_USER_ID -exec chown -h jobscheduler {} \;
  fi

  echo "JS7 entrypoint script switching to user account 'jobscheduler' to run start script"
  echo "JS7 entrypoint script starting Agent: exec su-exec jobscheduler:$JS_GROUP_ID /var/sos-berlin.com/js7/agent/bin/agent.sh start_docker" "${js_args[@]}"
  exec su-exec jobscheduler:$JS_GROUP_ID /var/sos-berlin.com/js7/agent/bin/agent.sh start_docker "${js_args[@]}"
else
  if [ "$BUILD_USER_ID" = "$JS_USER_ID" ]
  then
    if [ "$(id -u)" = "$JS_USER_ID" ]
    then
      echo "JS7 entrypoint script running for user id '$(id -u)'"
    else
      echo "JS7 entrypoint script running for user id '$(id -u)' cannot switch to user id '$JS_USER_ID', group id '$JS_GROUP_ID'"
      echo "JS7 entrypoint script missing permission to switch user id and group id, consider to omit the 'docker run --user' option"
    fi
  else
    echo "JS7 entrypoint script running for user id '$(id -u)' cannot switch image user id '$BUILD_USER_ID' -> '$JS_USER_ID', group id '$BUILD_GROUP_ID' -> '$JS_GROUP_ID'"
    echo "JS7 entrypoint script missing permission to switch user id and group id, consider to omit the 'docker run --user' option"
  fi

  echo "JS7 entrypoint script starting Agent: exec sh -c /var/sos-berlin.com/js7/agent/bin/agent.sh start_docker" "${js_args[@]}"
  exec sh -c "/var/sos-berlin.com/js7/agent/bin/agent.sh start_docker \"${js_args[*]}\""
fi

Line 22: The config folder available in the build directory is copied to the config sub-folder in the image. The parent folder var_<port> is determined from the HTTP port that the Agent is built for. This can be useful for creating an image with individual default settings in configuration files, see the JS7 - Agent Configuration Items article for more information.
Line 35 - 38: 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 relevant build arguments.
Line 41 - 44: 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 53 - 59: The image OS is updated and additional packages are installed (ps, netstat, bash).
Line 60: The most recent Java 11 package available with Alpine is applied. Agents can be operated with newer Java releases. However, stick to Oracle, OpenJDK or AdoptOpenJDK as the source for your Java LTS release. Alternatively you can use your own base image and install Java 1.8 or later on top of this. For details see Which Java versions is JobScheduler available for?
Line 61: The jobscheduler user account is created and is assigned the user id and group id handed over by the relevant build arguments. 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 61 - 62: Java releases might make use of /dev/random for random number generation. This is a bottleneck as random number generation with this file is blocking. Instead /dev/urandom should be used that implements non-blocking behavior. The change of the random file is applied to the Java security file.
Line 63 - 65: The jobscheduler user account is made the owner of installed files and the entrypoint script is made executable.
Line 82 - 84: The entrypoint script and Agent start script are executed and are dynamically parameterized from environment variables when starting the container.

Build Script

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

Build Script for Agent Image

#!/bin/bash

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="2.5.0"
JS_REPOSITORY="sosberlin/js7"
JS_IMAGE="$(basename "${SCRIPT_HOME}")-${JS_RELEASE//\./-}"

JS_USER_ID="$UID"

JS_HTTP_PORT="4445"
JS_HTTPS_PORT=

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=//'`
                           ;;
         --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=$SCRIPT_HOME/build/Dockerfile \
      --build-arg="JS_RELEASE=$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_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

Explanation:

Line 12 - 22: 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 the release of JS7 that you want to build an Agent for.
- 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 is by default the user id of the user running the build script.
- the HTTP port and HTTPS port: if the respective port is not specified then the Agent will not listen to a port for the associated 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 container's host. However, you can modify ports as required.
- 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 27 - 50: The above options can be overwritten by command line arguments like this:
Running the Build Script with Arguments
```
./build.sh --http-port=14445 --https-port=14443 --java-options="-Xmx1G"
```
Line 54 - 63: The effective docker build command is executed with arguments. The Dockerfile is assumed to be located in the build sub-directory of the current directory.

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JS7 - Agent Build of Container Image before Release 2.5.2

Introduction

Build Environment

Dockerfile

Build Script