Smart Mode

Smart Mode looks at the files you changed and processes only the environments and applications those changes can affect. It is what makes myks render without arguments fast on a large tree, locally and in CI.

Smart Mode is on whenever you run myks render or a plugin without positional arguments. Any selector (myks render ALL, myks render prod) turns it off.

How it works

Smart Mode asks Git for the changed files:

• always: git status --untracked-files, that is staged, unstaged and untracked changes;
• with --smart-mode.base-revision=<rev>: also git diff <rev>, every file that differs between <rev> and the working tree.

It then maps every changed path to environments and applications with the rules below. Decisions are based on paths, not on file content, so Smart Mode sometimes processes more than strictly necessary.

When nothing is affected (for example, only a README.md changed), myks exits before syncing or rendering anything. When Smart Mode cannot run — the project is not in a Git repository, Git fails, or the project uses KCL mode — myks logs a warning and processes everything; with --smart-mode.only-print, it fails instead.

Rules

Paths use the default naming conventions. <dir> stands for any of the per-application directories: vendir, lib, helm, ytt, ytt-pkg, static, argocd.

Everything

• lib/** — the root ytt library
• prototypes/_vendir/** — the shared vendir base, see sources.md

All applications of environments

A change at envs/<path>/ selects every environment at or below envs/<path>/, with all its applications:

• envs/<path>/env-data*.yaml
• envs/<path>/_env/ytt/**
• envs/<path>/_env/argocd/**
• envs/<path>/_env/static/**

A change in envs/env-data.ytt.yaml therefore selects every environment.

Applications of a prototype

• prototypes/<proto>/app-data*.yaml and prototypes/<proto>/<dir>/** select every application based on <proto>, in every environment.
• envs/<path>/_proto/<proto>/app-data*.yaml and envs/<path>/_proto/<proto>/<dir>/** select the applications based on <proto> in environments at or below envs/<path>/.

Single applications

• envs/<path>/_apps/<app>/app-data*.yaml and envs/<path>/_apps/<app>/<dir>/** select <app> in the environments at or below envs/<path>/ that have it.
• rendered/envs/<env-id>/<app>/** and rendered/argocd/<env-id>/app-<app>.yaml select <app> in that environment, so hand-made edits to rendered output are rendered over.
• An application listed in an environment but missing from rendered/envs/<env-id>/ is selected, so new applications get rendered.

Not watched

Changes to anything else select nothing, including .myks.yaml and files outside envs/, prototypes/, lib/ and rendered/. Render the affected environments explicitly after changing them, for example myks render prod.

Sync only

With myks render --sync, Smart Mode ignores changes that can only affect rendering, since they cannot change what gets downloaded:

• _env/ytt/, _env/argocd/ and _env/static/ directories;
• application and prototype directories other than vendir/ and lib/;
• rendered output, and applications missing from it.

Data-values files, vendir/ and lib/ directories, prototypes/_vendir/ and the root lib/ still count, because they feed the vendir configuration.

Previewing the selection

--smart-mode.only-print prints what would be processed and exits:

$ myks render --smart-mode.only-print

Smart Mode detected:
→ envs/prod/eu
    frontend
→ envs/stage
    ALL

$ myks render --smart-mode.only-print=json
{
  "envs/prod/eu": [
    "frontend"
  ],
  "envs/stage": null
}

Keys are environment directories; null and ALL mean all applications of every environment at or below that directory. The flag also works with explicit selectors, which makes it a quick way to check what myks render prod frontend would touch.

Smart Mode in CI

Uncommitted changes are rarely what CI should look at. Compare with the branch the change goes into:

myks render --smart-mode.base-revision=origin/main

The revision must exist in the checkout, so fetch enough history (for example, fetch-depth: 0 with actions/checkout). See gitops-ci.md for complete pipelines.