Scheduling with GitHub Actions

Daily Knowledge Drop

A GitHub Action can be configured to executed on a set schedule, and it's as simple as adding a line to the workflow YAML using Cron syntax.

As part of the development of this blog, there was a requirement to execute an Action on a schedule - which turned out to be easier than anticipated.

Cron

Quick intro to Cron syntax - if you are already familiar with this you can jump straight to how to implement in workflow YAML

The Cron syntax is used to define a schedule and consists of 5 fields separated by a space, with each field representing a unit of time.

Cron syntax

The structure is as follows:

A B C D E

A => minute (0-59)
B => hour (0-23)
C => day of the month (1-31)
D => month (1-12 or JAN-DEC)
E => day of the week (0-6 or SUN-SAT)

Each position/unit can have one of the following operators:

• * = any value
• , = value list separator
• - = range of value
• / step values

Cron examples

A few examples.

• 30 * * * *: executes at minute 30 of every hour of every day
• 15,45 03 * * 1,2: executes at minute 15 and 45 on hour 03 (3am) every Monday and Tuesday
• 10 18-20 * * SUN: executes at minute 10 on hour 18, 19 and 20 every Sunday
• 25/10 * * * *: executes every 10 minutes, starting at minute 25 (so minute 25, 35, 45, 55)

There are resources available online to assist in building up the Cron expression (see references below for an example website)

YAML updates

A GitHub Action is a way to automate a process related to a GitHub repository. In my example I use it to build and release this website every day.

The Action definition is stored as YAML as part of the repository, and defines the job(s) to perform as well as when to perform them.

Below is a snippet from this website's YAML file, relating to when the job should be executed.

# Controls when the workflow will run
on:
  # Triggers the workflow on the schedule
  schedule:
    - cron: '30 3 * * 1,2,3,4,5'
  # Allows for manual trigger of workflow
  workflow_dispatch:

# more omitted

In the above, we specified that the Action should run every on the schedule specified: Monday - Friday at 03:30, and also that the Action can be run manually.

Notes

Scheduling a Github Actions is really that simple. Actions are a powerful tool, and the ability to easily schedule them adds to their usefulness - anyone using GitHub repositories which require a workflow of any kind, should investigate how they can be leverage to automate (on a schedule if require) the required workflow.

References

Crontab Guru
GitHub Action Scheduling

Daily Drop 06: 08-02-2022

At the start of 2022 I set myself the goal of learning one new coding related piece of knowledge a day.
It could be anything - some.NET / C# functionality I wasn't aware of, a design practice, a cool new coding technique, or just something I find interesting. It could be something I knew at one point but had forgotten, or something completely new, which I may or may never actually use.

The Daily Drop is a record of these pieces of knowledge - writing about and summarizing them helps re-enforce the information for myself, as well as potentially helps others learn something new as well.