Tutorial: Build a container image - AWS Batch

Tutorial: Build a container image

You can use the AWS_BATCH_JOB_ARRAY_INDEX in a job definition in the command parameter. However, we recommend that you create a container image that uses the variable in an entrypoint script instead. This section describes how to create such a container image.

To build your Docker container image

  1. Create a new directory to use as your Docker image workspace and navigate to it.

  2. Create a file named colors.txt in your workspace directory and paste the following into it.

    red
orange
yellow
green
blue
indigo
violet

  3. Create a file named print-color.sh in your workspace directory and paste the following into it.

    Note

    The LINE variable is set to the AWS_BATCH_JOB_ARRAY_INDEX + 1 because the array index starts at 0, but line numbers start at 1. The COLOR variable is set to the color in colors.txt that's associated with its line number.

    #!/bin/sh
LINE=$((AWS_BATCH_JOB_ARRAY_INDEX + 1))
COLOR=$(sed -n ${LINE}p /tmp/colors.txt)
echo My favorite color of the rainbow is $COLOR.

  4. Create a file named Dockerfile in your workspace directory and paste the following content into it. This Dockerfile copies the previous files to your container and sets the entrypoint script to run when the container starts.

    FROM busybox
COPY print-color.sh /tmp/print-color.sh
COPY colors.txt /tmp/colors.txt
RUN chmod +x /tmp/print-color.sh
ENTRYPOINT /tmp/print-color.sh

  5. Build your Docker image.

    $ docker build -t print-color .

  6. Test your container with the following script. This script sets the AWS_BATCH_JOB_ARRAY_INDEX variable to 0 locally and then increments it to simulate what an array job with seven children does.

    $ AWS_BATCH_JOB_ARRAY_INDEX=0
while [ $AWS_BATCH_JOB_ARRAY_INDEX -le 6 ]
do
    docker run -e AWS_BATCH_JOB_ARRAY_INDEX=$AWS_BATCH_JOB_ARRAY_INDEX print-color
    AWS_BATCH_JOB_ARRAY_INDEX=$((AWS_BATCH_JOB_ARRAY_INDEX + 1))
done

    The following is the output.

    My favorite color of the rainbow is red.
My favorite color of the rainbow is orange.
My favorite color of the rainbow is yellow.
My favorite color of the rainbow is green.
My favorite color of the rainbow is blue.
My favorite color of the rainbow is indigo.
My favorite color of the rainbow is violet.