feat(syncwaves): add DAG for syncwaves v2 (alpha) #7437

[SebastienFelix]

This PR resolves #7437

This PR introduces a new concept to sync-waves : sync-groups, which allows to define groups of resources that could be synced independently using a DAG representing their dependencies.

To give some insights of what I am trying to achieve with this PR, I add a new layer to sync-waves in to order to define groups of resources that could be synced independently (in parallel) using sync waves. By adding a wave-group id and wave group dependencies, it allows to define a DAG operating on the different wave groups. Here is an example of resource definition and the expected behavior :

apiVersion: v1
kind: Pod
metadata:
name: label-demo
labels:
argocd.argoproj.io/sync-wave: -1
argocd.argoproj.io/sync-wave-group: 2
argocd.argoproj.io/sync-wave-group-dependencies: 0,1

This pod belongs to wave-group 2 with sync-wave value -1. It will be synced only when no more resources from sync-groups 0 and 1 needs to be synced.

How Does It Work Together?

Syncing process orders the resources in the following precedence:

The phase
The group with respect to group dependencies
The wave they are in (lower values first)
By kind (e.g. namespaces first)
By name

Hope it clarifies.

Checklist:

• Either (a) I've created an enhancement proposal and discussed it with the community, (b) this is a bug fix, or (c) this does not need to be in the release notes.
• The title of the PR states what changed and the related issues number (used for the release note).
• The title of the PR conforms to the Title of the PR
• I've included "Closes [ISSUE #]" or "Fixes [ISSUE #]" in the description to automatically close the associated issue.
• I've updated both the CLI and UI to expose my feature, or I plan to submit a second PR with them.
• Does this PR require documentation updates?
• I've updated documentation as required by this PR.
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• My new feature complies with the feature status guidelines.
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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 62.29%. Comparing base (b74cf45) to head (883f632).
⚠️ Report is 107 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #25282      +/-   ##
==========================================
+ Coverage   60.82%   62.29%   +1.46%     
==========================================
  Files         351      351              
  Lines       60439    49346   -11093     
==========================================
- Hits        36760    30738    -6022     
+ Misses      20757    15670    -5087     
- Partials     2922     2938      +16     

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[kahirokunn]

I really like this feature, but is there some issue preventing this PR from moving forward?

[tcapko]

Is there something to be done to help merge this sooner? This is really cool.