How to find out the cause of application failures?

To determine the causes of application failures, a comprehensive approach should be used, including the following steps:

1. Monitoring and metrics collection:

   • System metrics (CPU, RAM, Disk I/O, Network).
   • Application performance metrics (response time, request count, errors).
   • Business metrics (transaction count, conversion rate).
   • Tools: Prometheus, Grafana, Zabbix.

2. Log analysis:

   • System logs.
   • Application logs (errors, warnings, execution information).
   • Centralized log collection and analysis.
   • Tools: ELK Stack (Elasticsearch, Logstash, Kibana), Splunk.

3. Request tracing:

   • Tracking the request path through all microservices and system components.
   • Identifying bottlenecks and errors in the call chain.
   • Tools: Jaeger, Zipkin, OpenTelemetry.

4. Application profiling:

   • Analyzing resource consumption (CPU, memory) by specific parts of the code.
   • Finding "hot" spots and memory leaks.
   • Tools: VisualVM, JProfiler (for Java), pprof (for Go).

5. Memory dump analysis (core dumps):

   • Applications with critical errors may generate memory dumps containing the process state at the time of failure.
   • Analysis helps identify the cause of crashes (e.g., memory access violations).
   • Tools: gdb, windbg.

6. Histograms and distributions:

   • Analyzing the distribution of request execution times or other metrics can reveal deviations and anomalies.

7. Configuration analysis:

   • Incorrect configuration of the application, operating system, or network components can cause failures.

8. Audit and security logs:

   • Unusual activity or security breaches can cause failures.

9. Comparison with a working version or environment:

   • If a failure occurred after deployment, comparing with a previous version or a working environment can help identify the cause.

When a failure is detected, it is important to quickly get a complete picture using a combination of these methods.

Example of tool usage:

# View the last 100 lines of application logs
kubectl logs <pod_name> -n <namespace> --tail 100

# Search for errors in logs using grep
grep "ERROR" /var/log/myapp/application.log

# Check CPU usage with top
top -u <user>

# Get Prometheus metrics via API
curl http://prometheus.example.com/api/v1/query?query=http_requests_total