Add hint to keep version of node and meteor flexible

[SimonSimCity]

I am now planning on moving my own build script to using this package as multi stage build, and I found a neat trick in my script which might be cool to share to the users of this script.

When running my script, I have a docker-variable for the name of the base-image, which is filled with the value used in my current environment. Let me put this into an example.

In the environment of my project, I have a clear reference what version of meteor and nodejs I'm using.

A call of meteor node --version | cut -c2-99 reveals the version of nodejs and meteor --version | cut -c8-99 reveals the version of meteor.

So why not propose to start the build-script with:

ARG  METEOR_VERSION
ARG  NODE_VERSION

FROM geoffreybooth/meteor-base:${METEOR_VERSION}

[...]

FROM node:${NODE_VERSION}-alpine

[...]

And call docker build --build-arg NODE_VERSION=$(meteor node --version | cut -c2-99) --build-arg METEOR_VERSION=$(meteor --version | cut -c8-99) and use them in the multi stage build script? It's just a very neat trick, I think, people should get to know of.

But I sadly have to drop it since I cannot get a docker-build argument being passed on by another build-step. This means I cannot have a docker file which you just run and it will figure all this out 😢 Maybe it helps someone leaving it as a hint.

EDIT: Fixed the example of a Dockerfile file according to moby/moby#37345 (comment). Variables which I want to have available in all steps must be declared before the first FROM definition.

[GeoffreyBooth]

So https://github.com/disney/meteor-base/blob/master/src/Dockerfile already has ARG METEOR_VERSION. It doesn’t need NODE_VERSION because that’s set by when Meteor is installed.

Therefore I assume you’re talking about https://github.com/disney/meteor-base/blob/master/example/default.dockerfile, which is meant as example boilerplate for users to use in their own projects. So sure, we can at least put a comment in this file along the lines of “if you don’t want to hard-code the Meteor version, uncomment the next line”. I would be hesitant to make the ARG lines the default in the example, because that adds complexity in users needing to create a shell script or the like to kick off their building; I was trying to keep the build command as a simple docker-compose up. We could add the ARG lines and just have the argument values set in docker-compose.yml, but that just moves the hard-coding to another place.

So at the very least I’m fine with adding a comment and/or a note in the README, and I’m open to discussing any ways to further automate this; but I want to avoid users needing to use scripts to build, because that adds complexity and makes us need to figure out how to make that cross-platform (since I don’t want to exclude Windows users). Also something else to be aware of is that the example Dockerfile does change between Meteor versions; I’ve submitted PRs to node-fibers to make Fibers much more compatible with Alpine (it previously didn’t include an Alpine-compatible binary, and now it does) but the versions of Meteor using older node-fibers from before my PRs needs a lot more dependencies in the example Dockerfile in order to compile Fibers during the build.

[SimonSimCity]

Yes, adding a comment to the sample is all I'm asking for here. It's just to show the possibility.

Well ... I now also have to move away from it because I want to use docker hub and automated builds there and I haven't found a way to support it. But it could be a nice tweak for others, so I thought it would be good to mention it.

[SimonSimCity]

I've just written a build-script which allows you to 1. not use a lot of additional resources and 2. take the version numbers from the project itself. Here it is:

#!/bin/bash

METEOR_VERSION=$(cat ./.meteor/release | cut -c8-99)
NODE_VERSION=$(docker run --rm geoffreybooth/meteor-base:${METEOR_VERSION} meteor node --version | cut -c2-99 | grep -o "[0-9\.]*")

docker build --build-arg METEOR_VERSION=$METEOR_VERSION --build-arg NODE_VERSION=$NODE_VERSION .

Since this is a separate script (which I use on DockerHub because it allows to overwrite the build script) - where should I add this as a good flexible version?