Scenario: You are operating Nginx as an API gateway in a Kubernetes environment. Over time, you notice increased latency and occasional 502 errors. The API services themselves are healthy. The issue points to the middleware layer.
Symptoms: Increased P95 response times from 200ms to 2s, intermittent 502 Bad Gateway errors, and Nginx error logs showing "upstream timed out" or "connect() failed" messages.
Diagnosis:
1. Check Nginx error logs: tail -f /var/log/nginx/error.log
2. Check access logs with upstream response times: tail -f /var/log/nginx/access.log | awk '{print $NF}' (last field is upstream response time)
3. Inspect Nginx worker connections: curl http://localhost/nginx_status (requires stub_status module)
4. Look at system resource usage: top, vmstat, netstat.
5. Analyze configuration: check proxy_connect_timeout, proxy_read_timeout, worker_connections, keepalive settings.
Commands to diagnose:
- nginx -T to dump full config.
- ab -n 1000 -c 100 http://your-api-gateway/ for load testing.
- curl -w "@curl-format.txt" -o /dev/null -s http://your-api-gateway/endpoint (with timing file).
Risk Controls:
- Before making changes, take a backup of config files: cp /etc/nginx/nginx.conf /etc/nginx/nginx.conf.bak
- Use a staging environment to test changes.
- If changes involve reloading, use nginx -s reload rather than restart.
- For Kubernetes, update ConfigMap and rollout restart gradually.
Specific optimizations:
- Increase worker_connections (e.g., from 1024 to 4096) if many concurrent connections.
- Adjust keepalive for upstream: proxy_http_version 1.1; proxy_set_header Connection "";
- Increase proxy buffers: proxy_buffer_size 4k; proxy_buffers 8 4k;
- Consider using upstream with least_conn or ip_hash for load balancing.
- Enable caching or compression if applicable.
Rollback:
- If performance degrades after changes, revert config to backup: cp /etc/nginx/nginx.conf.bak /etc/nginx/nginx.conf && nginx -s reload
- In Kubernetes, revert ConfigMap and apply previous version.
Verification: - Monitor response times using a synthetic monitoring tool (e.g., Prometheus/Grafana) or run repeated curls. - Check error logs for reduction in timeout errors. - Compare P95 latency before and after.
When to submit an OpsGlobal ticket: - If tuning does not resolve the issue. - If you suspect network-level problems outside Nginx (e.g., upstream service latency, DNS issues). - If you need an expert review of architecture or advanced tuning (e.g., SSL termination, WebSocket support, rate limiting). - If the issue is intermittent and requires deep packet inspection or correlation across multiple metrics.
Use cases
Useful for teams handling Performance issues and needing a clear troubleshooting and delivery workflow.
Problem background
A practical guide for SREs on diagnosing and resolving Nginx performance issues when used as an API gateway middleware, with actionable steps and safety precautions.
Troubleshooting steps
Confirm impact and recent changes, collect logs, configuration and metrics, then apply fixes from low to high risk.
Command examples
Replace sample resource names with real values and store passwords, tokens and keys in environment variables.
Risks
Before production changes, confirm backups, access boundaries, change windows and rollback paths.
Rollback plan
Keep original configuration and release versions; roll back config, images or database changes if metrics degrade.
Deliverables
Root-cause notes, key commands, remediation steps, verification results and follow-up recommendations.
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