Tagging docker images

[samuelhwilliams]

At the moment it looks like BackstopJS only records a single docker image tag: latest. This means it's not easy to use a consistent, reproducible image without copying the Dockerfile and using that to generate a static image.

It would be great if this project could start tagging releases with unique references, as well as updating latest, so that those who want to (e.g. me) can reference a specific build to minimise the risk of an update to this library inadvertently breaking our tests in some way.

[garris]

I still don't know what I'm doing with docker. 😔

what needs to happen? Can you give me the steps? It's probably pretty easy right?

[samuelhwilliams]

What do you currently do to build and push a new docker image? I don't see the Dockerfile in this repo; do you have it somewhere else in source control? I see it now.

I presume you run something like docker build -t backstopjs/backstopjs .. This will default to building an image tagged as latest, and when you push this up, it'll overwrite the previous image tagged as latest.

The simplest thing to do is start explicitly including tags when you build and push your docker images. You can do this like so: docker build -t backstopjs/backstopjs:3.0.32 .. This will create an image tagged as 3.0.32 (the BackstopJS version used in the latest Docker image, which is probably a reasonable place to start, unless you expect to do ever update the dockerfile without updating the Backstop version). You can then push it up with docker push backstopjs/backstopjs:3.0.32.

The latest tag doesn't necessarily do what you expect, insofar as it doesn't track the latest image you've pushed. It's just another tag name. So if you also want to update latest, you could instead run docker build -t backstopjs/backstopjs:3.0.32 -t backstopjs/backstopjs:latest . and then push up both tags (separately as you can't push multiple tags at once).

This would help people integrate a specific version of Backstop rather than having to track latest or copy your Dockerfile and build the image locally.

[samuelhwilliams]

Apologies, just noticed this is already open in #562.

I will have a think about how to tie this into your existing hook so that it can be handled automatically.

[samuelhwilliams]

@garris Ok, so I assume you're using Docker Hub's automated builds, configured at https://hub.docker.com/r/backstopjs/backstopjs/~/settings/automated-builds.

Here you can add a tag rule (see below) which will automatically build Docker images with the same tag. All you'd need to do is start tagging your commits when you bump the version number. Once you push these tags up to GitHub, DockerHub will trigger the build and you'll have this problem neatly solved. 👍

You could potentially use a post-commit hook or a webhook to automatically create git tags when the version of BackstopJS is updated, in which case you wouldn't have to take any manual action. But that would be a bit more work up front. :)

(Edit: looks like your release tags have a 'v' prefix, so you'd need to change the pattern above to include a 'v' after the caret.)

[garris]

Oh I just saw your latest post. This makes sense. Let me try to get this going. I can probably do this on Friday. Thanks!

[garris]

@samuelhwilliams thank you for the tips -- that made it super easy! Ok. So now there is a latest and a tags build. I think maybe I should delete the latest rule -- I can't imagine anyone would want to pull from that.

I just pushed a new tag and docker started building...

Please let me know if that is working for you!

[samuelhwilliams]

Nice, this looks like a good set up. I'd probably keep latest even though people are unlikely to rely on it, as it makes it easy for people who are pulling the image and just want to play around before pinning the version.

It looks like the latest few builds in Docker Hub have failed due to being unable to pull BackstopJS through NPM. I can only think that maybe the latest versions aren't published yet?

Weirdly enough, I could also see the cancel button on the Docker Hub build. Haven't tried clicking it, but wonder if the settings are too permissive and maybe the public can cancel builds?

[garris]

@samuelhwilliams Ahh -- I see the fail too. So I guess that means I need to publish the new tagged version to NPM before pushing my tag to github. That makes sense. One question though...

In the ./docker file there is a BACKSTOPJS_VERSION property. Does this version need to match the tagged version -- IOW does this file need to be updated with the current tag each time I publish? Or can this value just be a semver? E.G. ^3.0.34

[samuelhwilliams]

Probably best to have the tag on the docker image match that of the BackstopJS version inside it, as that's what most people would expect to be the case.

It looks like the Dockerfile only uses BACKSTOPJS_VERSION with npm install, which only seems to accept specific version numbers, so it looks like we'll need to update Dockerfile BACKSTOPJS_VERSION in line with version in package.json.

Might be I can throw something together to automate/simplify some of these release processes/artifacts, if you would like. Not sure what you do at the moment for releasing to npm/docker/anywhere else. Is it all manual at the moment?

[Baltazardoung]

You can probably use a hook to automatically publish a tag using the version declared in your Dockerfile

It is then enough to add a sub folder "hooks" containing a file "post_push":

#!/bin/bash
eval $(grep -o 'BACKSTOPJS_VERSION=[^ ]*' $(dirname "$0")/../Dockerfile)

docker tag $IMAGE_NAME $DOCKER_REPO:$BACKSTOPJS_VERSION
docker push $DOCKER_REPO:$BACKSTOPJS_VERSION

Edit : See an example :

• eedb459
• https://hub.docker.com/r/hchristophe/backstopjs/tags/

[Baltazardoung]

In addition, if you want to use the version number referenced in the "package.json" file directly within the Dockerfile, you can use the build hook to retrieve this information and pass it as an argument to the build.

See 2931a59

[Baltazardoung]

The best solution was probably a mix of previous proposals.

1. Implementation of a single DockerHub rule based on a tag.
   
2. Updating Dockerfile and adding the build hook to pass the version as argument (extracted from the package.json file).

FROM node:8.5.0-alpine

ARG BACKSTOPJS_VERSION

ENV \
	PHANTOMJS_VERSION=2.1.1 \
	CASPERJS_VERSION=1.1.4 \
	SLIMERJS_VERSION=0.10.3 \
	BACKSTOPJS_VERSION=$BACKSTOPJS_VERSION \
#...

#!/bin/bash
BACKSTOPJS_VERSION=$(grep -Po '(?<="version": ")[^"]*' $(dirname "$0")/../../package.json)

docker build --build-arg BACKSTOPJS_VERSION=$BACKSTOPJS_VERSION -t $IMAGE_NAME .

3. Adding the "post_push" hook (to generate the "latest" image)

#!/bin/bash
docker tag $IMAGE_NAME $DOCKER_REPO:latest
docker push $DOCKER_REPO:latest

What do you think ?

[samuelhwilliams]

Sounds pretty good to me.

[garris]

Thank you @Baltazardoung and @samuelhwilliams! And many apologies for the late response Samuel!

I have an hour tomorrow to try to implement this. I would totally appreciate if either of you would be able to do a Skype call to make sure I don’t screw this up.😄 No worries either way—I’ll give it my best shot. Cheers!

[Baltazardoung]

@garris see pl #617 😄

[fusionfox]

Sorry, I got busy after raising #562 - happy to see that this got picked up 😄