# Phase 7: Deployer & Health Checker

**Status:** ✅ Complete
**Parent plan:** [PLAN.md](./PLAN.md)
**Domain:** backend

## Objective
Implement the core deployment orchestrator: pull → start container → configure NPM proxy → health check → success/rollback. Plus multi-instance support and notifications.

## Tasks

- [x] Task 1: Define deployer service struct — depends on Docker client, NPM client, store, notifier
- [x] Task 2: Implement deploy flow: pull image → create container → start → connect to network → configure proxy → health check
- [x] Task 3: Implement subdomain generation per convention: `stage-{stage}-{project}` for default, `stage-{stage}-{project}-{tag}` for specific
- [x] Task 4: Sanitize tags for DNS (dots → dashes, lowercase, truncate)
- [x] Task 5: Implement health checker — HTTP GET to `http://container:{port}{healthcheck_path}` with retries and timeout
- [x] Task 6: Implement rollback on health check failure — remove new container, delete NPM proxy host, update instance status
- [x] Task 7: Implement multi-instance support — multiple tags of same project/stage can run simultaneously
- [x] Task 8: Implement max_instances enforcement — remove oldest instance when limit reached
- [x] Task 9: Implement notification webhook — POST to configured URL on deploy success/failure
- [x] Task 10: Create deploy history records in store (status, timestamps, logs)
- [x] Task 11: Implement deploy log streaming — append log entries during deploy for real-time visibility

## Files to Modify/Create
- `internal/deployer/deployer.go` — main deploy orchestrator
- `internal/deployer/subdomain.go` — subdomain generation and DNS sanitization
- `internal/deployer/rollback.go` — rollback logic
- `internal/health/checker.go` — HTTP health checker with retries
- `internal/notify/notifier.go` — webhook notification sender

## Acceptance Criteria
- Full deploy flow works end-to-end (pull → proxy → health check)
- Failed health checks trigger automatic rollback
- Multi-instance: deploying a new tag doesn't stop existing instances
- max_instances removes oldest instance when exceeded
- Notifications fire on success and failure
- Deploy history is recorded with status and timestamps

## Notes
- Health check: 3 retries, 5s between retries, 10s timeout per attempt (configurable later)
- Subdomain pattern comes from global settings
- Notifications are fire-and-forget (don't block deploy on notification failure)
- Deploy logs should be structured entries (timestamp + message) for SSE streaming later
- The deployer is the central orchestrator — webhook handler and poller both call into it

## Review Checklist
- [ ] All tasks completed
- [ ] Rollback cleans up ALL resources (container, proxy, instance record)
- [ ] No goroutine leaks
- [ ] Error handling at every step of the deploy flow
- [ ] Subdomain generation produces valid DNS names

## Handoff to Next Phase
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