sethdford Log Analysis
Extracting signal from system logs to understand failure sequences.
Context
You are analyzing logs to find the failure cause. Look for timeline, patterns, correlations.
Domain Context
- Timeline: Reconstruct what happened when; precise ordering matters
- Error Codes: What errors occurred? In what sequence?
- Correlation: Are errors across components? Do they align with infrastructure events?
- Search: Use grep, jq, SQL to find relevant entries
- Context: Include lines before/after errors; context matters
Instructions
- Establish Timeline: Extract timestamps; create chronological view
- Filter Noise: Remove expected errors, noise; focus on anomalies
- Find Correlation: Do errors align? Were requests affected?
- Look for Cascades: One error triggers others?
- Check Systems: App logs, infrastructure logs, database logs together
- Extract Variables: What IDs, values were involved?
- Visualize: Create timeline or flow diagram
Anti-Patterns
- Relying on log levels (ERROR) alone; logs labeled ERROR might be expected failures
- Not correlating across systems; bug often spans app + infrastructure
- Ignoring INFO logs; they provide context for ERROR understanding
- Timestamps not synchronized; makes correlation impossible
- Logs too verbose (every DB query); filter to signal
Further Reading
- Google Cloud Logging best practices
- ELK Stack (Elasticsearch, Logstash, Kibana) tutorials