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git.stella-ops.org/docs/operations/runbooks/scanner-worker-stuck.md

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# Runbook: Scanner - Worker Not Processing Jobs
> **Sprint:** SPRINT_20260117_029_DOCS_runbook_coverage
> **Task:** RUN-002 - Scanner Runbooks
## Metadata
| Field | Value |
|-------|-------|
| **Component** | Scanner |
| **Severity** | Critical |
| **On-call scope** | Platform team |
| **Last updated** | 2026-01-17 |
| **Doctor check** | `check.scanner.worker-health` |
---
## Symptoms
- [ ] Scan jobs stuck in "pending" or "processing" state for >5 minutes
- [ ] Scanner worker process shows 0% CPU usage
- [ ] Alert `ScannerWorkerStuck` or `ScannerQueueBacklog` firing
- [ ] UI shows "Scan in progress" indefinitely
- [ ] Metric `scanner_jobs_pending` increasing over time
---
## Impact
| Impact Type | Description |
|-------------|-------------|
| **User-facing** | New scans cannot complete, blocking CI/CD pipelines and release gates |
| **Data integrity** | No data loss; pending jobs will resume when worker recovers |
| **SLA impact** | Scan latency SLO violated if not resolved within 15 minutes |
---
## Diagnosis
### Quick checks (< 2 minutes)
1. **Check Doctor diagnostics:**
```bash
stella doctor --check check.scanner.worker-health
```
2. **Check scanner service status:**
```bash
stella scanner status
```
Expected: "Scanner workers: 4 active, 0 idle"
Problem: "Scanner workers: 0 active" or "status: degraded"
3. **Check job queue depth:**
```bash
stella scanner queue status
```
Expected: Queue depth < 50
Problem: Queue depth > 100 or growing rapidly
### Deep diagnosis
1. **Check worker process logs:**
```bash
stella scanner logs --tail 100 --level error
```
Look for: "timeout", "connection refused", "out of memory"
2. **Check Valkey connectivity (job queue):**
```bash
stella doctor --check check.storage.valkey
```
3. **Check if workers are OOM-killed:**
```bash
stella scanner workers inspect
```
Look for: "exit_code: 137" (OOM) or "exit_code: 143" (SIGTERM)
4. **Check resource utilization:**
```bash
stella obs metrics --filter scanner --last 10m
```
Look for: Memory > 90%, CPU sustained > 95%
---
## Resolution
### Immediate mitigation
1. **Restart scanner workers:**
```bash
stella scanner workers restart
```
This will: Terminate current workers and spawn fresh ones
2. **If restart fails, force restart the scanner service:**
```bash
stella service restart scanner
```
3. **Verify workers are processing:**
```bash
stella scanner queue status --watch
```
Queue depth should start decreasing
### Root cause fix
**If workers were OOM-killed:**
1. Increase worker memory limit:
```bash
stella scanner config set worker.memory_limit 4Gi
stella scanner workers restart
```
2. Reduce concurrent scans per worker:
```bash
stella scanner config set worker.concurrency 2
stella scanner workers restart
```
**If Valkey connection failed:**
1. Check Valkey health:
```bash
stella doctor --check check.storage.valkey
```
2. Restart Valkey if needed (see `valkey-connection-failure.md`)
**If workers are deadlocked:**
1. Enable deadlock detection:
```bash
stella scanner config set worker.deadlock_detection true
stella scanner workers restart
```
### Verification
```bash
# Verify workers are healthy
stella doctor --check check.scanner.worker-health
# Submit a test scan
stella scan image --image alpine:latest --dry-run
# Watch queue drain
stella scanner queue status --watch
# Verify no errors in recent logs
stella scanner logs --tail 20 --level error
```
---
## Prevention
- [ ] **Alert:** Ensure `ScannerQueueBacklog` alert is configured with threshold < 100 jobs
- [ ] **Monitoring:** Add Grafana panel for worker memory usage
- [ ] **Capacity:** Review worker count and memory limits during capacity planning
- [ ] **Deadlock:** Enable `worker.deadlock_detection` in production
---
## Related Resources
- **Architecture:** `docs/modules/scanner/architecture.md`
- **Related runbooks:** `scanner-oom.md`, `scanner-timeout.md`
- **Doctor check:** `src/Doctor/__Plugins/StellaOps.Doctor.Plugin.Scanner/Checks/WorkerHealthCheck.cs`
- **Dashboard:** Grafana > Stella Ops > Scanner Overview