krontab

A crontab replacement for kubernetes.

You can use it to create cron jobs on a kubernetes cluster in a familiar crontab format. Krontab works by allowing you to create job templates which are used in kubernetes. Then create specific cron jobs using the crontab. Example:

# template: default
0 1 * * * echo hello  # name: test

Installation

Linux (x86 64-bit)

curl -L https://github.com/jacobtomlinson/krontab/releases/download/{LATEST VERSION}/krontab-linux-amd64 -o /usr/local/bin/krontab
chmod +x /usr/local/bin/krontab

Linux (arm 32-bit)

curl -L https://github.com/jacobtomlinson/krontab/releases/download/{LATEST VERSION}/krontab-linux-arm -o /usr/local/bin/krontab
chmod +x /usr/local/bin/krontab

OS X (64-bit)

curl -L https://github.com/jacobtomlinson/krontab/releases/download/{LATEST VERSION}/krontab-darwin-amd64 -o /usr/local/bin/krontab
chmod +x /usr/local/bin/krontab

Configuration

Krontab is configured with environment variables.

Env var	Default	Description
KRONTAB_NAMESPACE	default	The kubernetes namespace to use.
KRONTAB_OWNER	N/A	The owner of a cronjob. This will be used when creating jobs and will be used as a filter when listing them.

Usage

$ krontab help
Krontab is a crontab replacement for kubernetes.

You can use it to create cron jobs on a kubernetes cluster in a familiar crontab format.
Krontab works by allowing you to create job templates which are used in kubernetes. Then create
specific cron jobs using the crontab. Example krontab:

# Crontab example

# template: default
0 1 * * * echo hello  # name: test

Usage:
  krontab [flags]
  krontab [command]

Available Commands:
  create      Create a krontab resource
  delete      Delete a krontab resource
  edit        Edit a krontab resource
  get         Get krontab resources
  help        Help about any command
  list        List krontab resources
  version     Print the version number of krontab

Flags:
  -e, --edit-crontab   Edit the crontab
  -h, --help           help for krontab
  -l, --list-crontab   List the crontab

Use "krontab [command] --help" for more information about a command.

Templates

Krontab uses templates to turn your crontab into Kubernetes CronJob resources. You will get a default template which you can view with krontab get template default. You can create, edit and delete your own templates too.

$ krontab get template default
apiVersion: batch/v1beta1
kind: CronJob
metadata:
  name: test
spec:
  schedule: 0 */6 * * *
  jobTemplate:
    metadata:
      name: test
      krontabTemplate: default
    spec:
      template:
        metadata:
        spec:
          restartPolicy: Never
          containers:
            - name: test
              image: busybox
              command: ["echo", "hello"]
              resources:
                limits:
                  cpu: "1"
                  memory: 2G
                requests:
                  cpu: "0.25"
                  memory: 0.5G

Crontab

Krontab will automatically generate a crontab from your existing Kubernetes CronJob resources. You can edit them with krontab -e or krontab edit crontab. Adding new lines to your crontab will be mapped into new CrobJob resources. Editing lines will update them and deleteing lines will remove them.

$ krontab -e
# Welcome to krontab, a crontab like editor for Kubernetes cron jobs.
#
# This is a virtual file and was generated from the kubernetes API. Any edits you make here will be
# sent back to the kubernetes API to create/update/delete CronJob resources. Next time you open this crontab
# you may notice different formatting and comments to how you save it. Comments are meaningful and contain
# metadata about the job.
#
# Example job
# -----------
#
# # template: default
# 0 1 * * * echo hello world  # name: hello-world
#
# Templates
# ---------
#
# Krontab uses templates to turn your your crontab into kubernetes compliant CronJob resources. You will find
# a default template by running 'krontab get template default'. This is a minimal CrobJob resource with runs your
# command in a ubuntu container. When krontab creates your jobs it will replace the container command and schedule pattern
# in the template with the command and schedule pattern from the crontab.
#
# All cronjobs following a '# template: <name>' comment will be created using that template. If no template comments exist
# then the default template will be used.
#
# Names
# -----
# Kubernetes requires each job to have a name and is specified at the end of a job with a '# name: <name>' comment.
# If you do not specify a name one will be autogenerated.


# template: default
0 1 * * * echo hello world  # name: test

Contributing

Environment

This project requires Go to be installed. On OS X with Homebrew you can just run brew install go.

Running it then should be as simple as:

$ make
$ ./bin/krontab

Testing

make test