DigitalOcean Functions has support for Schedules

Check out How to Schedule Functions as an alternative to this tutorial.

To run functions on a schedule, you can create a function trigger and then specify a schedule using standard cron syntax.

DigitalOcean | App Platform Cron Worker

App Platform allows you to Build, deploy, and scale apps quickly using a simple, fully-managed infrastructure solution.
This tutorial shows you how to run scheduled jobs on App Platform using a Cron Worker.
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Getting Started

Architecture diagram

Introduction

In this tutorial, we'll guide you through the process of setting up a job scheduler in App Platform using a docker container that runs cron as an App Platform Worker. We'll talk you through the steps required to build the docker container in case you want to modify it and deploy the scheduler as an App Platform Worker using the smallest/cheapest container size. Defining your own scheduled jobs is as easy as modifying the included crontab file.

Prerequisites

1. A DigitalOcean account (Log in)
2. doctl CLI(tutorial)

Quick / Easy version

1. Fork this docker-cron repo
2. Add the following to your App Spec (yaml):

workers:
- dockerfile_path: Dockerfile
  github:
    branch: main
    deploy_on_push: true
    repo: <your-github-username>/docker-cron
  instance_count: 1
  instance_size_slug: basic-xxs
  name: docker-cron
  source_dir: /

3. Modify crontab in the forked repo to add your own cron jobs.

Hard / detailed version

Fork docker-cron

First import or fork https://github.com/DO-Solutions/docker-cron to a new Git repo on Github or Gitlab so that we can deploy our Docker Cron Worker

Modify Dockerfile

The provided Dockerfile is used by App Platform to build and run our Cron Worker, it should be modified to your liking

• ubuntu:22.04 base image is pulled
• cron and curl is installed, you can modify this line to include any other tools you may need to run your scheduled jobs

FROM ubuntu:22.04

RUN apt-get update \
    && apt-get install ca-certificates -y \
    && DEBIAN_FRONTEND=noninteractive apt-get -y --no-install-recommends install -y cron curl \
    # Remove package lists for smaller image sizes
    && rm -rf /var/lib/apt/lists/* \
    && which cron \
    && rm -rf /etc/cron.*/*

COPY crontab /hello-cron
COPY entrypoint.sh /entrypoint.sh

RUN crontab hello-cron
RUN chmod +x entrypoint.sh

ENTRYPOINT ["/entrypoint.sh"]

# https://manpages.ubuntu.com/manpages/trusty/man8/cron.8.html
# -f | Stay in foreground mode, don't daemonize.
# -L loglevel | Tell  cron  what to log about jobs (errors are logged regardless of this value) as the sum of the following values:
CMD ["cron","-f", "-L", "2"]

Modify crontab to define your own cron jobs

* * * * * curl http://sample-nodejs:8080 >/proc/1/fd/1 2>/proc/1/fd/2
# An empty line is required at the end of this file for a valid cron file.

Deploy to App Platform

Modify your App Spec

We're going to assume that you're adding docker-cron to an existing App Platform app. Use doctl to retrieve your existing apps App Spec and add docker-cron.

1. Retrieve App ID

doctl apps list

2. Use that ID to retrieve your apps App Spec

doctl apps spec get b6af73dc-8aba-4237-8dc9-b632ad379bd5 > appspec.yaml

alerts:
- rule: DEPLOYMENT_FAILED
- rule: DOMAIN_FAILED
name: walrus-app
region: nyc
services:
- environment_slug: node-js
  git:
    branch: main
    repo_clone_url: https://github.com/digitalocean/sample-nodejs.git
  http_port: 8080
  instance_count: 1
  instance_size_slug: basic-xxs
  name: sample-nodejs
  routes:
  - path: /
  run_command: yarn start
  source_dir: /

3. Add the Docker-cron worker

alerts:
- rule: DEPLOYMENT_FAILED
- rule: DOMAIN_FAILED
name: walrus-app
region: nyc
services:
- environment_slug: node-js
  git:
    branch: main
    repo_clone_url: https://github.com/digitalocean/sample-nodejs.git
  http_port: 8080
  instance_count: 1
  instance_size_slug: basic-xxs
  name: sample-nodejs
  routes:
  - path: /
  run_command: yarn start
  source_dir: /
workers:
- dockerfile_path: Dockerfile
  github:
    branch: main
    deploy_on_push: true
    repo: <your-github-username>/docker-cron
  instance_count: 1
  instance_size_slug: basic-xxs
  name: docker-cron
  source_dir: /

4. Update your app to deploy Docker-cron Worker

doctl apps update b6af73dc-8aba-4237-8dc9-b632ad379bd5 --spec appspec.yaml

Verify worker functionality

We can use doctl to retrieve our runtime logs and verify our cron is running, by default it will output to console

doctl apps logs b6af73dc-8aba-4237-8dc9-b632ad379bd5 --type=run

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Contact

Jack Pearce, Solutions Engineer - jpearce@digitalocean.com

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