crontab

A simple wrapper over docker to all complex cron job to be run in other containers.

Why?

Yes, I'm aware of mcuadros/ofelia (>250MB when this was created), it was the main inspiration for this project. A great project, don't get me wrong. It was just missing certain key enterprise features I felt were required to support where docker is heading.

Features

• Easy to read schedule syntax allowed.
• Allows for comments, cause we all need friendly reminders of what update_script.sh actually does.
• Start an image using image.
• Run command in a container using container.
• Ability to trigger scripts in other containers on completion cron job using trigger.
• Ability to share settings between cron jobs using ~~shared-settings as a key.

Config file

The config file can be specified in any of json, toml, or yaml, and can be defined as either an array or mapping (top-level keys will be ignored; can be useful for organizing commands)

• name: Human readable name that will be used as the job filename. Will be converted into a slug. Optional.
• comment: Comments to be included with crontab entry. Optional.
• schedule: Crontab schedule syntax as described in https://en.wikipedia.org/wiki/Cron. Examples: @hourly, @every 1h30m, * * * * *. Required.
• command: Command to be run on in crontab container or docker container/image. Required.
• image: Docker images name (ex library/alpine:3.5). Optional.
• container: Full container name. Ignored if image is included. Optional.
• dockerargs: Command line docker run/exec arguments for full control. Defaults to .
• trigger: Array of docker-crontab subset objects. Sub-set includes: image, container, command, dockerargs
• onstart: Run the command on crontab container start, set to true. Optional, defaults to false.

See config-samples for examples.

{
    "logrotate": {
        "schedule":"@every 5m",
        "command":"/usr/sbin/logrotate /etc/logrotate.conf"
    },
    "cert-regen": {
        "comment":"Regenerate Certificate then reload nginx",
        "schedule":"43 6,18 * * *",
        "command":"sh -c 'dehydrated --cron --out /etc/ssl --domain ${LE_DOMAIN} --challenge dns-01 --hook dehydrated-dns'",
        "dockerargs":"--it --env-file /opt/crontab/env/letsencrypt.env",
        "volumes":["webapp_nginx_tls_cert:/etc/ssl", "webapp_nginx_acme_challenge:/var/www/.well-known/acme-challenge"],
        "image":"willfarrell/letsencrypt",
        "trigger":[{
            "command":"sh -c '/etc/scripts/make_hpkp ${NGINX_DOMAIN} && /usr/sbin/nginx -t && /usr/sbin/nginx -s reload'",
            "container":"nginx"
        }],
        "onstart":true
    }
}

How to use

Command Line

docker build -t crontab .
docker run -d \
    -v /var/run/docker.sock:/var/run/docker.sock:ro \
    -v ./env:/opt/env:ro \
    -v /path/to/config/dir:/opt/crontab:rw \
    -v /path/to/logs:/var/log/crontab:rw \
    crontab

Use with docker-compose

1. Figure out which network name used for your docker-compose containers
   • use docker network ls to see existing networks
   • if your docker-compose.yml is in my_dir directory, you probably has network my_dir_default
   • otherwise read the docker-compose docs
2. Add dockerargs to your docker-crontab config.json
   • use --network NETWORK_NAME to connect new container into docker-compose network
   • use --name NAME to use named container
   • e.g. "dockerargs": "--it"

Dockerfile

FROM registry.gitlab.com/simplicityguy/docker/crontab

COPY config.json ${HOME_DIR}/

Logrotate Dockerfile

FROM registry.gitlab.com/simplicityguy/docker/crontab

RUN apk add --no-cache logrotate
RUN echo "*/5 *	* * *  /usr/sbin/logrotate /etc/logrotate.conf" >> /etc/crontabs/logrotate
COPY logrotate.conf /etc/logrotate.conf

CMD ["crond", "-f"]