Structured Logging

Problem

Logs are inconsistent plain text with no structure: different formats, missing context, and no way to filter or search effectively. When production issues occur, developers grep through thousands of unstructured log lines trying to piece together what happened. Critical information like user IDs, request IDs, or error codes are buried in freeform text.

Solution

Output logs as structured data with consistent fields rather than free-form text. This makes logs easier to search, filter, and analyze at scale.

Example

This demonstrates outputting logs as structured data with consistent fields rather than plain text, making logs searchable, filterable, and easier to analyze at scale.

// Log with structured data instead of plain text
logger.info('User logged in', {
  userId: 123,                              // Searchable user identifier
  timestamp: new Date().toISOString(),      // Standardized time format
  ipAddress: req.ip,                        // Network context
  userAgent: req.headers['user-agent']      // Client information
});

Benefits

• Makes logs searchable and filterable by specific fields.
• Enables automated analysis and alerting on log data.
• Provides consistent structure for debugging across the application.
• Integrates well with log aggregation and monitoring tools.

Tradeoffs

• Requires more verbose logging code compared to simple console.log.
• Needs logging library setup and configuration.
• Can bloat log output with structured metadata.
• May need log sanitization to prevent logging sensitive data.