Wait until Your Dockerized Database Is Ready before Continuing
In this video, we'll go over using a script to make sure your database is ready before running automated tests. Perfect for CI.
Quick Jump: Demo Video of the wait-until Script
Without some type of logic to ensure PostgreSQL, MySQL or whatever database you use is initialized and ready to go, you’re very likely going to run into failing tests in a Continuous Integration (CI) environment when you run tests that depend on your DB being available.
Technically you can use this script to wait until any command is ready but for this video, let’s focus on the very common use case of waiting for a database to be ready that’s running in Docker as part of a Docker Compose project.
Demo Video of the wait-until Script
Timestamped Table of Contents
- 1:15 – Taking a look at an example CI pipeline
- 2:28 – What happens when you don’t wait for your database
- 2:57 – Fixing things by introducing the wait-until script
- 4:43 – Seeing things work after calling the new wait-until script
- 5:49 – We looked at a PostgreSQL example but MySQL works too
- 6:08 – Investigating how we load in our environment variables
- 7:31 – Checking out the README file for the wait-until script
- 8:02 – Taking a quick look at the script itself
- 9:10 – Why bother using this script when other tools exist?
- 12:43 – You can install it anywhere, including your base Docker CI image
- 14:33 – Copy / paste’able examples for using this with PostgreSQL and MySQL
- 16:19 – Avoiding the input device is not a TTY error in a CI environment
- 17:11 – You’re in full control of redirecting the output of your wait command
- 18:46 – You can configure the timeout by passing in an optional 2nd argument
- 19:41 – Feel free to open a pull request if you have any improvements
Reference Links
- https://github.com/nickjj/wait-until
- https://buildasaasappwithflask.com
- https://github.com/vishnubob/wait-for-it
What do you do to ensure a Dockerized service is ready in CI? Let me know below.