I am trying to install cron via my Dockerfile, so that docker-compose can create a dedicated cron container by using a different entrypoint when it's built, which will regularly create another container that runs a script, and then remove it. I'm trying to follow the Separating Cron From Your Application Services section of this guide: https://www.cloudsavvyit.com/9033/how-to-use-cron-with-your-docker-containers/
I know that order of operation is important and I wonder if I have that misconfigured in my Dockerfile:
FROM swift:5.3-focal as build
RUN export DEBIAN_FRONTEND=noninteractive DEBCONF_NONINTERACTIVE_SEEN=true \
&& apt-get -q update \
&& apt-get -q dist-upgrade -y \
&& rm -rf /var/lib/apt/lists/*
WORKDIR /build
RUN apt-get update && apt-get install -y cron
COPY example-crontab /etc/cron.d/example-crontab
RUN chmod 0644 /etc/cron.d/example-crontab &&\
crontab /etc/cron.d/example-crontab
COPY ./Package.* ./
RUN swift package resolve
COPY . .
RUN swift build --enable-test-discovery -c release
WORKDIR /staging
RUN cp "$(swift build --package-path /build -c release --show-bin-path)/Run" ./
RUN [ -d /build/Public ] && { mv /build/Public ./Public && chmod -R a-w ./Public; } || true
RUN [ -d /build/Resources ] && { mv /build/Resources ./Resources && chmod -R a-w ./Resources; } || true
# ================================
# Run image
# ================================
FROM swift:5.3-focal-slim
RUN export DEBIAN_FRONTEND=noninteractive DEBCONF_NONINTERACTIVE_SEEN=true && \
apt-get -q update && apt-get -q dist-upgrade -y && rm -r /var/lib/apt/lists/*
RUN useradd --user-group --create-home --system --skel /dev/null --home-dir /app vapor
WORKDIR /app
COPY --from=build --chown=vapor:vapor /staging /app
USER vapor:vapor
EXPOSE 8080
ENTRYPOINT ["./Run"]
CMD ["serve", "--env", "production", "--hostname", "0.0.0.0", "--port", "8080"]
This is relevant portion of my docker-compose file:
services:
app:
image: prizmserver:latest
build:
context: .
environment:
<<: *shared_environment
volumes:
- $PWD/.env:/app/.env
links:
- db:db
ports:
- '8080:8080'
# user: '0' # uncomment to run as root for testing purposes even though Dockerfile defines 'vapor' user.
command: ["serve", "--env", "production", "--hostname", "0.0.0.0", "--port", "8080"]
cron:
image: prizmserver:latest
entrypoint: /bin/bash
command: ["cron", "-f"]
This is my example-scheduled-task.sh:
#!/bin/bash
timestamp=`date +%Y/%m/%d-%H:%M:%S`
echo "System path is $PATH at $timestamp"
And this is my crontab file:
*/5 * * * * /usr/bin/sh /example-scheduled-task.sh
My script example-scheduled-task.sh and my crontab example-crontab live inside my application folder where this Dockerfile and docker-compose.yml live.
Why won't my cron container launch?