feat(maintenance): maintenance page workflow, two replicas for landing page and service, test + staging on chart 2.4.0

[Mtze]

Why

During deploys EduIDE sometimes showed raw HTTP errors. EduIDE/EduIDE-Helm#47 (chart 2.4.0) adds a maintenance page served by Envoy while the landing page has no ready pod, and makes rolling updates keep a ready pod. This PR uses it.

Draft until chart 2.4.0 is released. Validate checks that every pinned chart version is published.

What

• .github/workflows/maintenance.yml (new, workflow_dispatch): environment, mode: on|off.
  • on: checks that the landing-maintenance-page policy exists, then scales landing-page-deployment to 0.
  • off: scales it back to landingPage.replicas (scripts/landing-replicas.sh: env values over _base.yaml over 1).
  • Both then curl the landing host and assert 503 + the maintenance page, or 200.
  • Shares the deploy-<env> concurrency group and runs the same cluster identity check as Deploy.
• deploy.yml: warns (annotation + summary) when the landing page is at 0 replicas before an upgrade, because the deploy ends maintenance.
• _base.yaml: landingPage.replicas: 2, service.replicas: 2. The service keeps its state in the cluster, so two pods are safe.
• bonn, mannheim: podDisruptionBudget.enabled: false. parma is a single node, where a PDB makes kubectl drain wait forever.
• Pins: test1-3, e2e, staging -> 2.4.0. Production, bonn and mannheim follow in a separate PR.
• Docs: README deploy table, docs/github-environments.md.

Tests

• scripts/test-deploy-logic.sh: replica resolution (chart default / _base / env override / unknown env / every real env), and PDBs off on the eduide cluster.
• With EDUIDE_CHART pointing at the EduIDE-Helm#47 branch, every environment renders against it.
• actionlint clean.

Verified on test1

Chart from EduIDE-Helm#47 with exactly these values:

• maintenance on (scale to 0) -> 503 + page.
• off (scale to 2) -> 200.
• A deploy while at 0 restores 2/2.

The workflow itself can only be dispatched once it is on main.

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[Copilot]

Copilot review overview

🟡 Changes recommended

Maintenance activation is not idempotent, and chart 2.4.0 is not yet published.

Review effort: Balanced
Findings: 1

Open (1)

• Maintenance-on reruns fail when no pods match · New

What changed in this PR

Adds controlled maintenance mode and improved landing/service availability.

Changes:

• Adds maintenance workflow and replica-resolution tests.
• Configures two replicas and disables PDBs on the single-node cluster.
• Pins test/staging environments to chart 2.4.0.

File	Description
.github/​workflows/​maintenance.yml	Adds maintenance controls and verification.
.github/​workflows/​deploy.yml	Warns when deployment ends maintenance.
scripts/​landing-replicas.sh	Resolves the configured landing replica count.
scripts/​test-deploy-logic.sh	Tests replica and PDB configuration.
environments/​_base.yaml	Sets landing and service replicas to two.
environments/​bonn.eduide.aet.cit.tum.de/​values.yaml	Disables PDBs on the single-node cluster.
environments/​mannheim.eduide.aet.cit.tum.de/​values.yaml	Disables PDBs on the single-node cluster.
environments/​test1.eduide.student.k8s.aet.cit.tum.de/​env.yaml	Pins chart 2.4.0.
environments/​test2.eduide.student.k8s.aet.cit.tum.de/​env.yaml	Pins chart 2.4.0.
environments/​test3.eduide.student.k8s.aet.cit.tum.de/​env.yaml	Pins chart 2.4.0.
environments/​e2e.eduide.student.k8s.aet.cit.tum.de/​env.yaml	Pins chart 2.4.0.
environments/​staging.eduide.student.k8s.aet.cit.tum.de/​env.yaml	Pins chart 2.4.0.
README.md	Documents maintenance operation.
docs/​github-environments.md	Documents workflow environment usage.

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