Commit c7494c1
feat(termination-watcher): deregister runners from GitHub on EC2 termination (#5055)
## Summary
Extends the existing termination-watcher Lambda to deregister GitHub
Actions runners from GitHub when their EC2 instances terminate. This
prevents stale "offline" runner entries from accumulating in the
organization/repository — a long-standing issue (#804, #1006, #2939)
affecting all users of the module.
### How it works
1. When an EC2 instance terminates, the Lambda reads the `ghr:Owner` and
`ghr:Type` tags from the instance
2. Authenticates to GitHub using the module's existing App credentials
(SSM parameters)
3. Finds the runner by instance ID in the runner name, then calls the
delete API
4. Errors are logged but never fail the Lambda — metrics collection
continues unaffected
### What's included
**Lambda changes:**
- `deregister.ts` — GitHub API deregistration logic reusing the module's
existing auth pattern (`createAppAuth` → installation token)
- Wired into both `termination.ts` (BidEvictedEvent) and
`termination-warning.ts` (Spot Interruption Warning)
- `ConfigResolver.ts` — adds `enableRunnerDeregistration` and
`ghesApiUrl` config from env vars
- 295-line test suite covering org/repo runners, not-found cases,
disabled feature, and error handling
**Terraform changes:**
- Passes GitHub App SSM parameter ARNs through the module chain to the
termination-watcher
- Adds SSM `GetParameter` IAM policy when deregistration is enabled
- Adds `PARAMETER_GITHUB_APP_ID_NAME`,
`PARAMETER_GITHUB_APP_KEY_BASE64_NAME`, `ENABLE_RUNNER_DEREGISTRATION`,
and `GHES_URL` environment variables to both Lambda functions
- Adds an `EC2 Instance State-change Notification` EventBridge rule
(state: `shutting-down`) that catches **all** termination types — not
just spot-specific events. This covers scale-down, manual termination,
ASG termination, and spot reclamation.
**New variables on `instance_termination_watcher`:**
- `enable_runner_deregistration` (bool, default `false`)
### Design decisions
- **Opt-in**: Disabled by default to avoid breaking existing
deployments. Enable with `enable_runner_deregistration = true`.
- **Reuses existing auth pattern**: Same `@octokit/auth-app` + SSM
approach used by the control-plane Lambda.
- **Reuses existing Lambda**: The state-change EventBridge rule targets
the same notification Lambda rather than creating a new one, since both
event types provide `detail['instance-id']`.
- **Graceful failure**: All deregistration errors are caught and logged.
If the runner is already removed, it logs and returns. The Lambda never
fails due to deregistration issues.
- **Supports Org and Repo runners**: Reads `ghr:Type` tag to determine
the correct API endpoint.
- **GHES compatible**: Passes through the `ghes_url` variable for GitHub
Enterprise Server deployments.
### Testing
- 44 unit tests pass (7 test files), including the new
`deregister.test.ts`
- Tested in production: manually terminated a runner instance → Lambda
triggered within seconds → runner successfully deregistered from GitHub
org
Fixes #804
---------
Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
Co-authored-by: SRE Engineer <sre-engineer@paperclip.ing>
Co-authored-by: Paperclip <noreply@paperclip.ing>
Co-authored-by: Brend Smits <brend.smits@philips.com>1 parent 79b73a8 commit c7494c1
28 files changed
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File tree
- lambdas
- functions/termination-watcher
- src
- modules
- multi-runner
- termination-watcher
- notification
- termination
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