docker-crontab

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

Supported tags and Dockerfile links

latest (Dockerfile)

Why?

Yes, I'm aware of mcuadros/ofelia (280MB), 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.
Run command on a instances of a scaled container using project.
Ability to trigger scripts in other containers on completion cron job using trigger.

Config.json

comment: Comments to be included with crontab entry. Optional.
schedule: Crontab schedule syntax as described in https://godoc.org/github.com/robfig/cron. Ex @hourly, @every 1h30m, * * * * * *. Required.
command: Command to be run on docker container/image. Required.
image: Docker images name (ex library/alpine:3.5). Optional.
project: Docker Compose/Swarm project name. Optional, only applies when contain is included.
container: Full container name or container alias if project is set. 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. Subset includes: image,project,container,command,dockerargs
onstart: Run the command on crontab container start, set to true. Optional, defaults to falsey.

See config.sample.json for examples.

[{
 	"schedule":"@every 5m",
 	"command":"/usr/sbin/logrotate /etc/logrotate.conf"
 },{
 	"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":"--env-file /opt/crontab/env/letsencrypt.env -v webapp_nginx_tls_cert:/etc/ssl -v 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'",
 		"project":"conduit",
 		"container":"nginx"
 	}],
 	"onstart":true
 }]

How to use

Command Line

docer build -t crontab .
docker run -d \
    -v /var/run/docker.sock:/var/run/docker.sock:ro \
    -v /usr/bin/docker:/usr/bin/docker:ro \
    -v /path/to/config/dir:/opt/crontab:rw \
    crontab

Dockerfile

FROM willfarrell/crontab

COPY config.json ${HOME_DIR}/

Logrotate Dockerfile

FROM willfarrell/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"]

TODO

Have ability to auto regenerate crontab on file change (signal HUP?)
Run commands on host machine (w/ --privileged?)
Write tests
Setup TravisCI

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