docker-crontab

A simple wrapper over docker to all complex cron job to be run in other containers. Note, this is a maintained fork of willfarrell/docker-crontab.

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.
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 file

The config file can be specifed 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. Ex @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.
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-samples 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

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

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
Add dockerargs to your docker-crontab config.json
- use --network NETWORK_NAME to connect new container into docker-compose network
- use --rm --name NAME to use named container
- e.g. "dockerargs": "--network my_dir_default --rm --name my-best-cron-job"

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