App Service Troubleshooting
Common Issues Matrix
| Symptom | Likely Cause | Action |
|---|---|---|
| High CPU / memory | Runaway process, inefficient code | Use Process Explorer via Kudu, scale up |
| Deployment failure | Build error, locked files, quota | Check Kudu logs at https://APP.scm.azurewebsites.net/api/deployments to look for details on build errors, locked files or lack of storage quota |
| App crash / restart | Unhandled exception, OOM kill | Review Event Log and STDERR in Diagnose & Solve |
| Slow responses | Downstream dependency, no caching | Enable request tracing, check dependency calls |
| 502 / 503 errors | App not starting, port conflict | Check STDERR logs, verify startup command |
| TLS / domain errors | Certificate expired, DNS mismatch | az webapp config ssl list, verify CNAME |
| Health check failure | Endpoint not returning 200 | Verify health check path responds within 2 min |
High CPU / Memory Diagnosis
Diagnose:
bash
# Check app metrics
az monitor metrics list --resource APP_RESOURCE_ID \
--metric "CpuPercentage,MemoryPercentage" --interval PT1M --output table
# View running processes via ARM Processes API (Entra ID auth)
az rest --method get \