[MINOR] §12: No published Docker image — exporter built locally on every start

[mvillmow]

Evidence

docker-compose.yml:153-155, exporter/Dockerfile

Description

The argus-exporter is built from local source (build: ./exporter) on every docker compose up. There is no published Docker image in a registry, no versioned image tag, and no way to reference a specific exporter version without a git SHA. This makes deployment reproducibility dependent on the local source tree.

Part of #100

[mvillmow]

Implementation Plan

Now I have everything needed to write a precise implementation plan.

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Implementation Plan: Issue #149 — Publish argus-exporter to GHCR

1. Objective

Publish a versioned argus-exporter Docker image to GitHub Container Registry (GHCR) so that deployments reference a specific, registry-pinned image instead of building from local source on every docker compose up.

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2. Approach

• Add a new GitHub Actions workflow (publish-exporter.yml) that builds and pushes ghcr.io/<ORG>/argus-exporter with dual tags (:latest + :<SHORT_SHA>) on every merge to main, plus a weekly Monday rebuild for base-image security patches.
• Harden the exporter/Dockerfile with a SHA256-pinned base image and multi-stage build (builder + slim runtime) to satisfy the existing deps-version-sync required check (no :latest tags) and reduce image size.
• Gate publishing behind a Trivy HIGH/CRITICAL scan.
• Replace build: ./exporter in docker-compose.yml with image: ghcr.io/<ORG>/argus-exporter:latest (with a .env-overridable pin for production use).
• PRs only build/test — no push. The if: github.event_name != 'pull_request' guard ensures this.

Key decisions:

• Use docker/build-push-action (not Podman) to stay consistent with the existing _required.yml Docker-based checks.
• SHA256-pin python:3.14.0-slim in the Dockerfile to satisfy dockerfile-version-guard learnings — prevents silent base-image changes between weekly rebuilds.
• Keep the runtime stage as slim as possible: no pip cache, no test deps, only exporter.py and its runtime requirements.

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3. Files to Create

Path	Description
.github/workflows/publish-exporter.yml	Build + Trivy scan + GHCR push workflow; triggers on push to main paths exporter/** and weekly cron

Note (from prior learnings): The Write tool is blocked for GitHub Actions workflow files — create this file with a Bash heredoc.

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4. Files to Modify

exporter/Dockerfile

• Current: single-stage FROM python:3.14.0-slim (no digest pin)

• Changes:

  1. Add multi-stage build: builder stage installs dependencies; runtime stage copies only the app.
  2. Pin the base image with its SHA256 digest: FROM python:3.14.0-slim@sha256:<64-char-digest>.
  3. Add ENV EXPORTER_VERSION=0.1.0 for inspectability.
  4. COPY exporter.py /exporter.py in the runtime stage (already minimal; no compiled artifacts, so multi-stage mainly enforces the pattern and allows future dep additions without bloating the runtime image).

  Final structure:

  FROM python:3.14.0-slim@sha256:<digest> AS builder
  WORKDIR /build
  COPY exporter.py .
  
  FROM python:3.14.0-slim@sha256:<digest> AS runtime
  ENV EXPORTER_VERSION=0.1.0
  COPY --from=builder /build/exporter.py /exporter.py
  CMD ["python", "/exporter.py"]

docker-compose.yml (lines ~152-155, argus-exporter service)

• Change: Replace build: ./exporter with image: ${ARGUS_EXPORTER_IMAGE:-ghcr.io/mvillmow/argus-exporter:latest}
• This allows ARGUS_EXPORTER_IMAGE=ghcr.io/mvillmow/argus-exporter:<SHA> in .env for production pinning while defaulting to :latest for local dev.

justfile

• Add a build-exporter recipe for local development builds: docker build -t argus-exporter:local ./exporter
• Add a run-exporter-local recipe that sets ARGUS_EXPORTER_IMAGE=argus-exporter:local for offline testing.

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5. Implementation Order

1. Fetch the SHA256 digest for python:3.14.0-slim by running docker pull python:3.14.0-slim and extracting the digest from docker inspect output.
2. Update exporter/Dockerfile — add SHA256-pinned multi-stage build with ENV EXPORTER_VERSION.
3. Create .github/workflows/publish-exporter.yml via Bash heredoc (blocked for Write tool) with:
   • Triggers: push to main on exporter/** path + schedule: "0 6 * * 1" + workflow_dispatch
   • on: pull_request job that only builds (no push) for PR validation
   • build-and-push job: checkout → GHCR login via GITHUB_TOKEN → build image → Trivy scan (aquasecurity/trivy-action@0.30.0, HIGH,CRITICAL, ignore-unfixed: true, exit-code: 1) → push :latest + :<SHORT_SHA> tags — guarded by if: github.event_name != 'pull_request'
4. Update docker-compose.yml — replace build: ./exporter with image: using the env-var pattern.
5. Update justfile — add build-exporter and run-exporter-local recipes.
6. Verify the _required.yml deps-version-sync check still passes (no bare :latest in image fields — the docker-compose change uses a variable default, which may need adjustment if the check greps the literal string).

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6. Verification

Check	Command / Method
Dockerfile builds locally	docker build -t argus-exporter:test ./exporter — must succeed
Trivy scan passes	trivy image --severity HIGH,CRITICAL --exit-code 1 argus-exporter:test
docker-compose config valid	just validate (runs docker compose config --quiet)
CI deps-version-sync check	Inspect _required.yml logic; ensure the image: value with env-var default doesn't trip the :latest guard
Published image pullable	After merge to main, docker pull ghcr.io/mvillmow/argus-exporter:latest and verify the image runs python /exporter.py on port 9100
SHA tag available	docker pull ghcr.io/mvillmow/argus-exporter:<SHORT_SHA> matches the merge commit
Stack starts with registry image	Set ARGUS_EXPORTER_IMAGE=ghcr.io/mvillmow/argus-exporter:latest in .env, run just start, confirm argus-exporter container pulls rather than builds

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7. Skills Used

Invoked during planning:

• hephaestus:advise — consulted team knowledge base before drafting the plan

Team knowledge base skills referenced from Prior Learnings:

Skill	How applied
podman-ci-containerization	Dual-tag pattern (:latest + :<SHORT_SHA>), push-on-merge-only guard, GHCR login via GITHUB_TOKEN, weekly rebuild cron, Write-tool-blocked workaround (Bash heredoc)
dockerfile-version-guard	SHA256-pinned FROM lines, strict [a-f0-9]{64} digest pattern, == pinning rule
dockerfile-env-version-pin	ENV EXPORTER_VERSION=x.y.z for inspectability
docker-multistage-build	Builder + runtime stage separation for size reduction and future-proofing
pin-install-script-tag	Not directly applied (no curl-piped installer in this Dockerfile), but noted as irrelevant to this specific exporter

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Generated by Claude Code Planner

[mvillmow]

Created 4 follow-up issue(s): #393, #394, #395, #396

[mvillmow]

Verified ALREADY-DONE. Evidence documented in PR #502 body: .github/workflows/publish-exporter-image.yml already publishes to GHCR. Closing as no further work needed.