Support Windows

[imjasonh]

This issue tracks work needed to make Tekton run on a Kubernetes cluster with Windows nodes. Please contribute your use cases, ideas and experience.

First, some assumptions I've been operating under:

1. Tekton controller components themselves don't need to run on Windows nodes. The cluster could have N Linux nodes and M Windows nodes, run the controller on one of the Linux nodes, and run requested workloads on Windows nodes. If we decide full-Windows clusters are the goal, then we'll need to expand this work to cover getting controller components built and running for Windows.
2. The user has to explicitly specify they want a TaskRun to execute on a Windows node, using nodeSelector -- Tekton isn't responsible for somehow detecting that a TaskRun should run on a Windows node. We might change how a TaskRun's Pod is generated based on the user's specification, but ideally we wouldn't have to, for simplicity.

If either of these are contentious, or you have more to add, please comment.

Next, some things I'm fairly sure will break without trying:

1. Building Images: Entrypoint binary injection is done today by prepending a step containing the entrypoint binary, which copies that binary to /tekton/entrypoint -- to support Windows, that binary will have to be built to run on Windows, and will have to be based on some minimal Windows image (i.e., not distroless as it is today). This is doable with manifest lists, which ko has some support for. Likewise, internal support images used to implement resources (git-init, creds-init, google/cloud-sdk, etc., will need to be able to be built for Windows)

2. File Paths: Step ordering works by looking for files to exist at some predetermined path, and those paths are specified using /-separated paths (/tekton/tools, /tekton/downward/ready, etc.) -- this is likewise true for /workspace, /tekton/home, etc. If we decide in the future to use fsnotify to watch files instead of polling, we'll have to make sure that works for Windows too (or fallback to polling).

3. Script Mode: Script mode is implemented today by writing an executable file to /tekton/scripts/something, then invoking it as the Command in the step container. Writing this file and making it executable, as well as where it exists, will require work to support Windows.

Sources:

• https://cloud.google.com/blog/products/containers-kubernetes/how-to-deploy-a-windows-container-on-google-kubernetes-engine

[afrittoli]

@imjasonh any special reason for this to be on the priority list? I will remove it for now, feel free to bring it back to the API WG if needed

[tekton-robot]

Stale issues rot after 30d of inactivity.
Mark the issue as fresh with /remove-lifecycle rotten.
Rotten issues close after an additional 30d of inactivity.
If this issue is safe to close now please do so with /close.

/lifecycle rotten

Send feedback to tektoncd/plumbing.

[tekton-robot]

Rotten issues close after 30d of inactivity.
Reopen the issue with /reopen.
Mark the issue as fresh with /remove-lifecycle rotten.

/close

Send feedback to tektoncd/plumbing.

[tekton-robot]

@tekton-robot: Closing this issue.

In response to this:

Rotten issues close after 30d of inactivity.
Reopen the issue with /reopen.
Mark the issue as fresh with /remove-lifecycle rotten.

/close

Send feedback to tektoncd/plumbing.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[vdemeester]

/remove-lifecycle rotten
/remove-lifecycle stale
/reopen

[tekton-robot]

@vdemeester: Reopened this issue.

In response to this:

/remove-lifecycle rotten
/remove-lifecycle stale
/reopen

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.