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System Overview and Architecture
- Document the system architecture and components
- Map out dependencies and integrations
- Identify critical paths and failure points
- Create system topology diagrams
- Document data flow and communication patterns
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Common Issues Identification
- Collect historical support tickets and issues
- Interview team members about frequent problems
- Analyze error logs and monitoring data
- Review user feedback and complaints
- Identify patterns in system failures
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Troubleshooting Framework
- Establish systematic diagnostic procedures
- Create problem isolation methodologies
- Document escalation paths and procedures
- Set up logging and monitoring checkpoints
- Define severity levels and response times
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Diagnostic Tools and Commands
## Essential Diagnostic Commands
### System Health
```bash
# Check system resources
top # CPU and memory usage
df -h # Disk space
free -m # Memory usage
netstat -tuln # Network connections
# Application logs
tail -f /var/log/app.log
journalctl -u service-name -f
# Database connectivity
mysql -u user -p -e "SELECT 1"
psql -h host -U user -d db -c "SELECT 1"
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Issue Categories and Solutions
Performance Issues:
### Slow Response Times
**Symptoms:**
- API responses > 5 seconds
- User interface freezing
- Database timeouts
**Diagnostic Steps:**
1. Check system resources (CPU, memory, disk)
2. Review application logs for errors
3. Analyze database query performance
4. Check network connectivity and latency
**Common Causes:**
- Database connection pool exhaustion
- Inefficient database queries
- Memory leaks in application
- Network bandwidth limitations
**Solutions:**
- Restart application services
- Optimize database queries
- Increase connection pool size
- Scale infrastructure resources
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Error Code Documentation
## Error Code Reference
### HTTP Status Codes
- **500 Internal Server Error**
- Check application logs for stack traces
- Verify database connectivity
- Check environment variables
- **404 Not Found**
- Verify URL routing configuration
- Check if resources exist
- Review API endpoint documentation
- **503 Service Unavailable**
- Check service health status
- Verify load balancer configuration
- Check for maintenance mode
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Environment-Specific Issues
- Document development environment problems
- Address staging/testing environment issues
- Cover production-specific troubleshooting
- Include local development setup problems
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Database Troubleshooting
### Database Connection Issues
**Symptoms:**
- "Connection refused" errors
- "Too many connections" errors
- Slow query performance
**Diagnostic Commands:**
```sql
-- Check active connections
SHOW PROCESSLIST;
-- Check database size
SELECT table_schema,
ROUND(SUM(data_length + index_length) / 1024 / 1024, 1) AS 'DB Size in MB'
FROM information_schema.tables
GROUP BY table_schema;
-- Check slow queries
SHOW VARIABLES LIKE 'slow_query_log';
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Network and Connectivity Issues
### Network Troubleshooting
**Basic Connectivity:**
```bash
# Test basic connectivity
ping example.com
telnet host port
curl -v https://api.example.com/health
# DNS resolution
nslookup example.com
dig example.com
# Network routing
traceroute example.com
SSL/TLS Issues:
openssl s_client -connect example.com:443
curl -vI https://example.com
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Application-Specific Troubleshooting
Memory Issues:
### Out of Memory Errors
**Java Applications:**
```bash
# Check heap usage
jstat -gc [PID]
jmap -dump:format=b,file=heapdump.hprof [PID]
# Analyze heap dump
jhat heapdump.hprof
Node.js Applications:
node --inspect app.js
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Security and Authentication Issues
### Authentication Failures
**Symptoms:**
- 401 Unauthorized responses
- Token validation errors
- Session timeout issues
**Diagnostic Steps:**
1. Verify credentials and tokens
2. Check token expiration
3. Validate authentication service
4. Review CORS configuration
**Common Solutions:**
- Refresh authentication tokens
- Clear browser cookies/cache
- Verify CORS headers
- Check API key permissions
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Deployment and Configuration Issues
### Deployment Failures
**Container Issues:**
```bash
# Check container status
docker ps -a
docker logs container-name
# Check resource limits
docker stats
# Debug container
docker exec -it container-name /bin/bash
Kubernetes Issues:
kubectl get pods
kubectl describe pod pod-name
kubectl logs pod-name
kubectl get svc
kubectl port-forward pod-name 8080:8080
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Monitoring and Alerting Setup
- Configure health checks and monitoring
- Set up log aggregation and analysis
- Implement alerting for critical issues
- Create dashboards for system metrics
- Document monitoring thresholds
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Escalation Procedures
## Escalation Matrix
### Severity Levels
**Critical (P1):** System down, data loss
- Immediate response required
- Escalate to on-call engineer
- Notify management within 30 minutes
**High (P2):** Major functionality impaired
- Response within 2 hours
- Escalate to senior engineer
- Provide hourly updates
**Medium (P3):** Minor functionality issues
- Response within 8 hours
- Assign to appropriate team member
- Provide daily updates
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Recovery Procedures
- Document system recovery steps
- Create data backup and restore procedures
- Establish rollback procedures for deployments
- Document disaster recovery processes
- Test recovery procedures regularly
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Preventive Measures
- Implement monitoring and alerting
- Set up automated health checks
- Create deployment validation procedures
- Establish code review processes
- Document maintenance procedures
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Knowledge Base Integration
- Link to relevant documentation
- Reference API documentation
- Include links to monitoring dashboards
- Connect to team communication channels
- Integrate with ticketing systems
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Team Communication
## Communication Channels
### Immediate Response
- Slack: #incidents channel
- Phone: On-call rotation
- Email: alerts@company.com
### Status Updates
- Status page: status.company.com
- Twitter: @company_status
- Internal wiki: troubleshooting section
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Documentation Maintenance
- Regular review and updates
- Version control for troubleshooting guides
- Feedback collection from users
- Integration with incident post-mortems
- Continuous improvement processes
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Self-Service Tools
- Create diagnostic scripts and tools
- Build automated recovery procedures
- Implement self-healing systems
- Provide user-friendly diagnostic interfaces
- Create chatbot integration for common issues