Advanced Troubleshooting

This section covers more complex issues and advanced diagnostic techniques to resolve difficult problems.

Common Advanced Issues

Sudden spikes in CPU or memory usage can significantly degrade performance. Here’s how to diagnose:

Identify the Culprit Process: Use system monitoring tools (e.g., Task Manager on Windows, top or htop on Linux/macOS) to find the process consuming excessive resources.
Analyze Application Logs: Check application-specific logs for errors or unusual activity that might correlate with high resource usage.
Check for Infinite Loops or Memory Leaks: In custom applications, look for code patterns that could lead to resource exhaustion.
Consider System Updates: Ensure your operating system and all relevant software are up to date, as patches often address performance issues.

Tip: Sometimes, a simple restart of the problematic service or application can temporarily resolve high resource usage.

When network issues are intermittent or affect specific services, deeper investigation is needed:

Traceroute/Pathping: Use traceroute (Linux/macOS) or tracert (Windows) to identify network hops where latency or packet loss occurs.
Packet Analysis: Tools like Wireshark can capture and analyze network traffic to pinpoint the source of errors, malformed packets, or unexpected behavior.
DNS Resolution Issues: Test DNS resolution using nslookup or dig. Ensure DNS servers are reachable and configured correctly.
Firewall Rules: Verify that firewall rules on the server, client, and any intermediate network devices are not blocking necessary traffic.

Important: Before making changes to network configurations, ensure you have a backup or understand the potential impact.

Investigating unexpected service shutdowns requires a systematic approach:

Event Logs/System Logs: Examine the operating system's event logs (Windows Event Viewer, /var/log/syslog or journalctl on Linux) for errors or warnings immediately preceding the crash.
Application Crash Dumps: If available, analyze crash dump files generated by the application for detailed insights into the failure point.
Resource Constraints: Ensure the service has sufficient RAM, disk space, and file handle limits.
Configuration Errors: Double-check configuration files for syntax errors or incorrect parameters.

Example command to check recent logs on systemd systems:

sudo journalctl -u your-service-name.service -n 50 --no-pager

Slow application performance can stem from various sources:

Database Queries: Slow or inefficient database queries are a common bottleneck. Analyze query execution plans and optimize indexes.
Application Code Profiling: Use profiling tools to identify slow functions or code sections within the application itself.
External API Dependencies: If your application relies on external services, check their response times and availability.
Caching Issues: Ensure caching mechanisms (e.g., Redis, Memcached) are functioning correctly and configured appropriately.

Performance Monitoring Tools: Prometheus, Grafana, New Relic, Datadog.
Log Aggregation Tools: Elasticsearch/Logstash/Kibana (ELK stack), Splunk, Graylog.
Profiling Tools: Visual Studio Profiler, gprof, perf, Xdebug.
Network Analyzers: Wireshark, tcpdump.
System Auditing: Auditd (Linux), Sysmon (Windows).