Vinz

Optimizing docker image

Մι∩z•thedev · Follow Published in Coding · 6 min read · 1 day ago __ 👏65k 💬321 🔖 ⤴️ __ Dive is a utility to browse docker image https://github.com/wagoodman/dive.

Sandwich

Basically a docker image is a sandwich whose slices are called steps and stages. The FROM instruction in the Dockerfile says copy that sandwich, I’ll customize it with my toppings…

There you go !

• What was the sandwich made of before I customized it ?
• Have I really customized it the way I intended ?
• No hidden craps into it ?
• Have I not forgot my credit card number into it ?

Dive let you lift each slice and check the ingredients the previous cook put in, the ingredients you put as well. Hence you can ponder if all the stuff was really necessary and in case the answer is no, try to remove some to make the sandwich still good but more digestible. Let’s trim down the fat and move the belly swiftly !

Upgrade

I had to upgrade my Dive command-line utility, in order to browse my docker images, after my Docker Desktop upgrade to 4.29.

Indeed, docker changed image format to be OCI compatible. My Dive was v0.10.0. Check that with dive -v. Hopefully v0.12.0 fixes the issue. Get it with elevated choco install -y dive --version=0.12.0

dive my csharp project

dive bookingapi

• I found the most changing files while experimenting, the appsettings.*.json, should advantageously be moved toward the last stage in the dockerfile, after the build and publish, so that all previous stages are restored from cache. Prior to that, I moved the appsettings.*.json off the project directory, above indeed, so that they are excluded from the build.
• I noticed some packages have a cohesive way of changing, so I split the dotnet restore and dotnet build stages in several chunks, ordered by compilation priority or something that would probably help speeding up, like Business -> Libs -> Infra -> App
• I’m still looking for a way to multi-stage plenty-lot-dependencies project build . . .