feat(satellite): enable headless standalone mode

[SuryaPratapIIIT]

Allows the satellite to operate without connection to Ground Control. Skips registration, heartbeats, and state replication schedulers, relying exclusively on local configuration.

• Fixes: #
• CLI & Environment Options: Added the --headless CLI flag and HEADLESS environment variable support.
• Bypassed GC Requirements: Skipped required arguments validation (--token, --ground-control-url, --harbor-registry-url) on startup if running in headless mode.
• Lifecycle Overhaul: Disabled registration (ztrScheduler), status reporting/heartbeats (statusScheduler), and remote state replication (stateScheduler) from launching during startup when headless mode is active.
• Config Initialization: Extended the ConfigManager to track headless mode and bypass GC URL validation.

Verification

• Ran local test suite: go test ./...
• Verified standalone execution using --headless flag.

Summary by CodeRabbit

• New Features
  • Added a headless startup mode configurable through the --headless CLI flag or HEADLESS environment setting.
  • Headless mode allows startup without token, Ground Control, or Harbor registry URL validation.
  • Background scheduling and status reporting are disabled in headless mode.
• Bug Fixes
  • Standard mode validation and startup behavior remain unchanged.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Pro Plus

Run ID: 3ee152ef-74c6-48b8-b49e-217d11b8c81c

📥 Commits

Reviewing files that changed from the base of the PR and between 341cb42 and 1f54aa9.

📒 Files selected for processing (5)

• cmd/satellite/main.go
• internal/env/harbor-satellite.go
• internal/satellite/satellite.go
• pkg/config/manager.go
• pkg/config/validate.go

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📝 Walkthrough

Walkthrough

The satellite now supports headless mode through the HEADLESS environment setting or --headless CLI flag. Headless mode bypasses selected validation and skips ZTR, state replication, and status-report scheduler startup.

Changes

Headless satellite mode

Layer / File(s)	Summary
Headless input and wiring internal/env/harbor-satellite.go, cmd/satellite/main.go	Adds the Headless configuration field, loads it from HEADLESS or --headless, prints a startup message, and passes the value to configuration initialization.
Headless configuration validation pkg/config/manager.go, pkg/config/validate.go	Stores headless state in ConfigManager and skips Ground Control URL validation during initialization, reload, and default enforcement when headless mode is enabled.
Headless scheduler startup internal/satellite/satellite.go	Skips ZTR, state replication, and status-report scheduler creation and startup for headless satellites. Non-headless behavior remains unchanged.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Possibly related issues

• container-registry/harbor-satellite issue 227: Covers the headless Satellite mode, including flags, environment settings, validation bypasses, and scheduler disabling.

Possibly related PRs

• container-registry/harbor-satellite#515: Changes the centralized environment loader used by the headless configuration wiring.

Suggested labels: enhancement

Suggested reviewers: vg006

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely describes the main change: enabling headless standalone mode for the satellite.
Description check	✅ Passed	The description explains the headless mode, lists the main changes, and documents verification with tests and standalone execution.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[gitar-bot]

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[codacy-production]

Up to standards ✅

🟢 Issues 0 issues

Results:
0 new issues

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🟢 Metrics 0 complexity · 0 duplication

Metric	Results
Complexity	0
Duplication	0

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[cubic-dev-ai]

No issues found across 5 files

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[vg006]

@SuryaPratapIIIT

Thank you for your interest in Harbor Satellite, but I encourage you to look into the project and discuss with the maintainers and commuinty, before proceeding with the PRs directly.

Architecturally, Harbor Satellite is dependent on Ground Control(GC) and it must. There has never been an discussion/proposal to decouples Satellite from GC and making it completely independent. Satellite may bootstrap with the local configs, but that doesn't mean it neither require GC nor to report GC.

Hence this PR may get closed anytime. Thank you.

[SuryaPratapIIIT]

@vg006 Hyy Vijay , that's my fault I haven't discussed about the context to the maintainers and jumped directly to PR.
Next time i will definately discuss about it to the maintainers of the project.

Thank You .