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Scope

  • JobScheduler Agent is operated with a Docker container. 
  • Prerequisites
    • Consider to prepare the files indicated with chapter Build.

Build

The following files are required for the build context:

  • Dockerfile
  • Start Script start_jobscheduler_agent.sh
  • JobScheduler Agent tarball as available from SOS for download.

Dockerfile

  • Download: Dockerfile

    Dockerfile 
    FROM openjdk:8
LABEL maintainer="Software- und Organisations-Service GmbH"

# default user id has to match later run-time user
ARG USER_ID=$UID

# provide build arguments for release information
ARG JS_MAJOR=1.13
ARG JS_RELEASE=1.13.3

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

# add and extract tarball
COPY jobscheduler_unix_universal_agent.${JS_RELEASE}.tar.gz /usr/local/src/
RUN test -e /usr/local/src/jobscheduler_unix_universal_agent.${JS_RELEASE}.tar.gz && \
    tar xfvz /usr/local/src/jobscheduler_unix_universal_agent.${JS_RELEASE}.tar.gz && \
    rm /usr/local/src/jobscheduler_unix_universal_agent.${JS_RELEASE}.tar.gz

# make default user the owner of directories
RUN groupadd --gid ${USER_ID:-1000} jobscheduler && \
    useradd --uid ${USER_ID:-1000} --gid jobscheduler --home-dir /home/jobscheduler --no-create-home --shell /bin/bash jobscheduler && \
    chown -R jobscheduler:jobscheduler /var/sos-berlin.com

# copy and prepare start script
COPY start_jobscheduler_agent.sh /usr/local/bin/
RUN chmod +x /usr/local/bin/start_jobscheduler_agent.sh

# prepare logs directory
RUN mkdir -p /var/sos-berlin.com/jobscheduler_agent/var_4445/logs && chown -R jobscheduler:jobscheduler /var/sos-berlin.com/jobscheduler_agent/var_4445/logs

# expose volume for storage persistence
# VOLUME /var/sos-berlin.com/jobscheduler_agent/var_4445

# allow incoming traffic to port
EXPOSE 4445

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

CMD ["/usr/local/bin/start_jobscheduler_agent.sh"]
  • Explanations
    • Line 1: We start from an Alpine image that includes JDK 8. Newer Java version can be used, see Which Java versions is JobScheduler available for?
    • Line 5: Consider that $UID provides the numeric ID of the account that the JobScheduler Agent installation inside the Docker container is performed for. This numeric ID typically starts above 1000 and should correspond to the account that is used on the Docker host, i.e. the account on the Docker Host and the account inside the container should use the same numeric ID. This mechanism simplifies exposure of the Docker container's file system.
    • Line 8-9: Adjust the JobScheduler release number as required.
    • Line 16-19: The Agent tarball is copied and extracted to the container.
    • Line 22-24: An account and group "jobscheduler" is created that is handed over ownership of installed files.
    • Line 27-28: The start script is copied to the container, see below chapter Start Script.
    • Line 37: Port 4445 is exposed for later mapping. This port is used for the connection between JobScheduler Master and Agent.
    • Line 40: The account "jobscheduler" that is the owner of the installation is exposed for later mapping. This account should be mapped at run-time to the account in the Docker Host that will mount the exposed volume.
    • Line 42: The start script is executed to launch the JobScheduler Agent daemon.

Start Script

  • Download: start_jobscheduler_agent.sh

    Start Script
    #!/bin/sh

/var/sos-berlin.com/jobscheduler_agent/bin/jobscheduler_agent.sh start -http-port=4445 && tail -f /dev/null
  • Explanations
    • Line 3: The standard start script jobscheduler_agent.sh is used. The tail command prevents the start script from terminating in order to keep the container alive.

Build Command

There are a number of ways how to write a build command, find the following example:

  • A typical build command could look like this:

    Build Command
    #!/bin/sh

IMAGE_NAME="agent-1-13"

docker build --no-cache --rm --tag=$IMAGE_NAME --file=./build/Dockerfile --build-arg="USER_ID=$UID" ./build
  • Explanations
    • Consider use of the --build-arg that injects the USER_ID environment variable into the image with the numeric ID of the account running the build command. This simplifies later access to the volume that optionally can be exposed by the Dockerfile as the same numeric user ID and group ID inside and outside of the container are used.

Run

There are a number of ways how to write a run command, find the following example:

  • A typical run command could look like this:

    Run Command
    #!/bin/sh

IMAGE_NAME="agent-1-13"
RUN_USER_ID="$(id -u $USER):$(id -g $USER)"

mkdir -p /some/path/logs

docker run -dit --rm --user=$RUN_USER_ID --hostname=$IMAGE_NAME --network=js --publish=5445:4445 --volume=/some/path/logs:/var/sos-berlin.com/jobscheduler_agent/var_4445/logs:Z --name=$IMAGE_NAME $IMAGE_NAME
  • Explanations
    • Using a common network for JobScheduler components allows direct access to resources such as ports within the network.
    • The RUN_USER_ID variable is populated with the numeric ID of the account and the group that executes the run command. This value is assigned the --user option in order to inject the account information into the container (replacing the account specified with the USE jobscheduler instruction in the Dockerfile.
    • Port 4445 for access to JobScheduler Agent by a Master can optionally be mapped to some outside port. This is not required if a network is used.
    • Specify a logs directory to be created that is referenced with the --volume option to expose the log directory of the JobScheduler Agent for reading. Avoid to modify log files in this directory and to add new files.


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