Docker Buildx, Cache, and Immutable Image Tags Phase 32 created reproducible images. Phase 33 builds them in CI using Buildx and GitHub Actions cache. Every release image receives an immutable tag tied to the full Git commit SHA. Mutable labels such as main can exist for convenience, but deployments should record and promote the immutable SHA-tagged artifact.
sha-tagged github.sha → Buildx → image → GHCR
What this changes in TaskFlow • web image + api image
• Buildx gha cache
• sha- tag
• Do not rebuild during deployment
Release identity tags: type=sha,format=long,prefix=sha-
# deployment candidate ghcr.io/<owner>/taskflow-api:sha-${{ github.sha }}
Current Docker action lines verified: setup-buildx v4, metadata v6, build-push v7.
Containers package a process and its runtime assumptions. The lesson is not memorizing Docker commands; it is making those assumptions repeatable and observable.
Restate the goal of “Docker Buildx Cache and Immutable Image Tags” as one observable behavior. Write the success signal before touching code.
Trace the boundary map: source + lockfile → build context → image layers → container process → health signal. Mark the one boundary this lesson changes.
Inspect the current repository state and record the exact files, route, table, or runtime involved. Avoid creating an abstraction before you can name the existing owner.
Implement the smallest vertical slice. Add one coherent change, run the narrowest verification command, and read the output before continuing.
Connect the slice to TaskFlow’s phase artifact: .github/workflows/ci.yml plus release/deploy workflows that build once, tag by commit SHA, and gate promotion.. Verify behavior from the outside as a user or API client would.
Create one controlled failure that is safe to reproduce. Predict the symptom first, capture evidence, locate the earliest broken boundary, then fix only that cause.
Close the reference and rebuild or explain the core change from memory. Record what you would monitor or test before trusting the same change in production.
FROM node:24-alpine AS build
WORKDIR /app
RUN corepack enable
COPY package.json pnpm-lock.yaml pnpm-workspace.yaml ./
COPY apps/api/package.json apps/api/package.json
RUN pnpm install --frozen-lockfile
COPY . .
RUN pnpm --filter api buildDo not copy this as a finished answer. Predict what each boundary does, type the smallest useful slice, run it, then compare the result with your prediction.
Inspect container logs and PID 1 command; confirm the process stays in foreground and required config exists.
Check bind address, exposed/published ports, network namespace, and health endpoint.
Without copying the final source, create a second small scenario that applies “Docker Buildx Cache and Immutable Image Tags” to a different TaskFlow resource or input. Write the acceptance criteria first, implement it, and provide the evidence that each criterion is satisfied.
Create CI triggered by pull_request with read-only contents permission and explicit concurrency cancellation.
Use the smallest change that demonstrates this lesson. Stop after it works and capture evidence.Rebuilding different artifacts in each environment
Predict the symptom before causing the failure. Then locate the earliest boundary where reality diverges from expectation.Why does this responsibility live here, what input does it trust, what output proves success, and what would go wrong if another layer owned it?
If your explanation is vague, repeat the boundary trace before moving on.Close the reference. Reproduce the core idea from memory or explain the exact request/data flow aloud. Then check your diff or notes for accidental shortcuts that bypass validation, authorization, error handling, or verification earned in earlier phases.