Define tag policies for images

[sbose78]

Let's use this issue to discuss the exhaustive list of tag policies we would like to support. We'll do the API design as part of a different discussion.

[qu1queee]

@sbose78 thanks for this. Definitely not to use latest.

I think I´m more inclined on a digest, because a digest ensures that a container will use always the same image, unless the digest is changed. For the digest I see two options:

1. :@digest : This can come from the last commit of the source repository. Or a combination of things.

2. :tag@digest: This one is more complex, I know crio-o didn´t supported this till recently and that buildah have strong opinions on this. I think with this one you add one more layer of security making sure that the tag matches the digest.

For the :tag policy, I´m not that much a fan, because then we will need to have control on increasing any of the MAJOR.MINOR.PATCH semantic versioning numbers.

[zhangtbj]

Hi Enrique,

I think they are two different level requirements.

• digest is used for internal that the container can choose the unique image by using the digest, but the end-user doesn't care about that, or they even cannot even remember that easily.

• tag is a configuration in Build for end-user, that the end-user can choose which image version they want to build and use. For example, the end user just want to build some test image, or they want to bump a new tag to their application new release version such as MAJOR.MINOR.PATCH

For the better design, We(our internal) should use the digest somewhere to make sure the container or end user uses the actual image they want. But I think it is not urgent now n, I think it is an enhancement for maybe 3Q or future delivery. (Knative images also with the digest)

For tag it is an important feature for us now, we should allow end user to have this capability to build different tag images without always changing the build definition

[sbose78]

The digest isn't something we can set right? It's a unique identifier which the container registry provides us upon pushing an image.

From a policy perspective, I see two policies that sound implementable to me ( there could be more )

• semantic versioning x.y.z
• git hash

[zhangtbj]

Yep, but I think we still need the NONE and MANUAL policies as well.

for the pay account docker registry, it may not allow me to pull lots of test image with different image tags, it may cost me lots of money. So NONE policy just use the latest tag is enough.

For Manual policy, the user should have the capability to control what tag they would like, the custom tag, like for docker.io/myimage:test, or for docker.io/myimage/test:v1-test.

Both of this basic policies are also not hard to implement in our controller logic :)

[sbose78]

The None and Manual policies are both supported today, without being explicit about it. Users may or may not specify tags today.

When we do introduce tag policies in our API/CRD, when the user skips that attribute, the current behaviour would kick in without the need of explicitly calling it a Manual or None policy.

What do you think?

[zhangtbj]

Yes, I agree the None and Manual policies are supported now.

But the Manual policy is not good now. The end user has to:

• modify the output.image setting in build CR and save
• run a new buildRun just for the new tag of the built image.

That is why we are providing a PR: xiujuan95@61f2113

so that we can JUST change to a new output.image or a new tag parameter in buildRun, so that the end user can trigger a new buildRun with the new parameter to build a new different tag of image and WITHOUT modify the build config...

[sbose78]

I feel uncomfortable making changes to the BuildRun to be able to support that when we could modify the spec.output.image in the Build CR itself :(

modify the output.image setting in build CR and save

Curious, why is this an issue?

[zhangtbj]

It comes from our user experince from UI,

We won't ask end user to just kubectl apply the build resource, we should ask user to do from UI or Cli.

Then what we should provide to end user?

• end user provide the resource and build related configurations on UI and create a build
• Auto trigger a new buildRun at the first time, or we click a Start build button to start a new buildRun for the execution
• Next time, if user want to have a new buildRun and with different settings, like resourceLimit, serviceAccount now, we should pop up a dialog after end user click the Start Build button, then end user to config some parameters, then click Build, then we trigger a new BuildRun with new parameters.
• so that the end user don't need to modify those setting in Build config from UI then trigger the buildRun by button.

I think it is a good UX for end user.

Build should just keep the static source or build policy related data, and for buildRun, we can have some custom parameters to build a new image without two steps: modify build -> trigger new buildRun from UI for image tag (can use output.image, or a new tag parameter in buildRun).

But yes, as you see, we didn't provide the PR, we can discuss and confirm in the issue first.

Or any other comment about the overwrite rule or comments? :)

[smoser-ibm]

@sbose78 Let me share my viewpoint (using a concrete example): Assume you have a production build setup. So you'd have a BuildDefinition that is shared across the teams and that specifies the base parameters - buildFrom: master, buildOutput: myProdImage, CPU: 4 etc.
Every time someone/something triggers a build, a buildRun is created from that BuildDefinition (and the specs would be copied from the BuildDefinition to the BuildRun, and I could potentially overwrite something on the buildRun if I chose to (eg use 8 CPUs for that run)).
I think so far we agree on that scenario.
Now there are two potential scenarios how I can make a more substantial change to the system: Let's assume I want to test something that is sitting on a different branch (myTestBranch).
Option A ("The Kubernetes Way") would be to take the BuildDef, change branch to myTestBranch, and do a kubectl apply to create a buildRun of that. In our example, that is a bad practice because
a) This build Definition is not only used by me
b) It would still potentially output to buildOutput: myProdImage which I might not want (as there is further automation that picks up that image and deploys it)
So in my view of the world, a BuildDefintion is a higher-level construct than an "K8s resource", and different rules apply. Therefore, we a proposing an option B) where in my scenario I would NOT touch the build definition at all, but rather create a BuildRun from the standard BuildDef but override branch to myTestBranch and buildOutputto myTestImage instead. Then there is no need to change this back in the BuildDefiniton(and if my test is succesful I'd use git to merge myBranch into master and let if flow again). Hope this makes sense.
/FYI @qu1queee @zhangtbj

[qu1queee]

My 2 cents on this:

Purely speaking about overriding via BuildRun, and based on the following statement so that we can JUST change to a new output.image or a new tag parameter in buildRun, this is what Im thinking:

• We need to have a common understanding on what does each CRD means. I think a Build CRD hosts all configurations on what to build(e.g. source, output, details on the source like contextDir, etc). A BuildRun is the executor block, which host configurations on how to build(e.g. which service-account to use when building, resources constrains for the container that will execute the build, which Build to use, etc). Modifying the output of the image build in the BuildRun does not fit on the concepts of the CRDs meaning. Yes, we can modify configurations on the BuildRun, but only configurations related to the role of the CRD. In the future we might be able to modify more things on the BuildRun like timeouts, but only because timeouts are related to the execution block, not the configuration on what to build.

• For the example of already having a Build and a BuildRun, and the user requiring a change on the Build, then the user needs to update the Build and two things can happen:

  1. After changing an existing Build, a new BuildRun is automatically triggered. You can change your Build many times, the BuildRun will always have an snapshot of the Build used for that particular build mechanism, so that if you change the Build later again, you can see the original Build config inside your BuildRun.
  2. After changing an existing Build, A new BuildRun needs to be manually applied.

• For the example of having a single Build used for other people. I honestly will not do this if I was a developer. There is no need to share a Build, a Build is such an small artifact that everyone can define their own, and work on their own Build separately.

• For It would still potentially output to buildOutput: myProdImage which I might not want (as there is further automation that picks up that image and deploys it) . I think then you should have a particular Build for prod, and another Build for stage, and another for dev, etc. This adds more control for you and less error prone

[zhangtbj]

• In my opinion, the serviceaccount or timeouts now can defined in buildRun, but does end user really want to modify or set in each buildRun OFTEN? I think most of the case, one time setting is enough for them.
  But for image tag or even git revision, from a developer perspective, end user will change or use a different one MORE often then serviceaccount, timeouts and resourceLimit which we have.

• From Tekon implementation, we can see, they also don't allow to overwrite any setting from TaskRun spec, and support set sa, timeout and resource in taskrun. But they provide the Params mechanism, so that end user can define ANYTHING in Task as a param and overwrite it in Taskrun by using a new defined param. So first of all, this should be a vaild requirement, but we don't support this kind of params way.

For the example of having a single Build used for other people. I honestly will not do this if I was a developer. There is no need to share a Build, a Build is such an small artifact that everyone can define their own, and work on their own Build separately.

If then, I think we are back to the old Knative Build way, which just provides a Build CR, that everyone just have a build, if want to run a new Build, then modify any parameter in the build and trigger. No share and define their own.
That is not good and why community moves to Tekton way to provide the Task and Taskrun.

If we can define anything in the Build, why we still need the BuildRun? Why we still need BuildStrategy shared? Everytime, we modify the build and re-trigger it is enough.

So I also think, they are two requirements now:

• How to run a new build just with the new image tag from end user side
• How we support parameter overwrite

But for the first Beta release, we just require the first one.
And another idea, I am not sure if we can separate the output.image in Build as:

  output:
    imageUrl: image-registry.openshift-image-registry.svc:5000/build-examples/nodejs-ex
    tag: v0.11.0 (default is latest)

so that ONLY the output.tag can be set from buildRun, then we are also fine for that.
And it also should be ok for the style of Manual image policy, I think then the tag should be the outcome of the image policy(like other auto-generation tag policies) which can be the part of the execution, and be overwritten by the buildRun side.