🔗 Golang concurrency explained

If you want to learn about Golang, you’ll pretty quickly run into its main selling points:

• Simplicity

• Easy concurrency

I agree with both of those, but as a PHP/javascript developer, understanding its concurrency model was a tiny bit harder than I expected (skill issues, I know).

A few months ago, I started writing a “cleanup” script for one of my side projects, and I realized this is the perfect script to showcase the basics of Golang concurrency.

The project was a code-running platform such as LeetCode. You are presented with a challenge, you write your code and submit it. It supports PHP, Javascript, Go, MySQL, and Redis (there are MySQL and Redis-related challenges). To execute your submission fast, it creates containers in advance. Instead of creating a container on the fly when you submit your code (which is very slow), it maintains a container pool. So at any given moment, there are (let’s say) 3 running PHP containers, 3 running node containers, etc.

For local development, I didn’t use Docker (skill issues, again), so there were dozens (if not hundreds) of containers on my laptop. On production, it uses a docker-in-docker image so there are only ReelCode-related containers on the host machine, and these containers run the container pool with hundreds of containers ready to execute your code.

So I needed a cleanup script that stops and removes these containers from my laptop. But if the script works sequentially it takes a very long time to run. If stopping and removing a container takes 1 second, it takes almost a minute to remove 50 of them.