logging

Logging Infrastructure

This package provides structured logging infrastructure for the GraphQL service using Go's standard log/slog package.

Features

• Structured Logging: JSON and text format support
• Request Tracing: Request ID and correlation ID support
• Layer-Specific Loggers: Specialized loggers for each architecture layer
• Configurable Levels: Debug, Info, Warn, Error levels
• Context Propagation: Request context flows through all layers

Usage

Basic Logger Setup

import "github.com/captain-corgi/go-graphql-example/internal/infrastructure/logging"

// Create logger factory
factory := logging.NewLoggerFactory(config.LoggingConfig{
    Level:  "info",
    Format: "json",
})

// Get base logger
logger := factory.GetLogger()
logger.Info("Application started")

Layer-Specific Loggers

// Domain layer
domainLogger := factory.GetDomainLogger()
domainLogger.LogEntityCreated(ctx, "User", "user-123")

// Application layer
appLogger := factory.GetApplicationLogger()
appLogger.LogUseCaseStarted(ctx, "CreateUser", map[string]interface{}{
    "email": "user@example.com",
})

// Infrastructure layer
infraLogger := factory.GetInfrastructureLogger()
infraLogger.LogDatabaseQuery(ctx, "SELECT * FROM users", time.Millisecond*50)

// Interface layer
interfaceLogger := factory.GetInterfaceLogger()
interfaceLogger.LogHTTPRequest(ctx, "POST", "/query", 200, time.Millisecond*100)

Request Tracing

// Add request ID to context
ctx = logging.WithRequestID(ctx, "req-12345")

// Add correlation ID to context
ctx = logging.WithCorrelationID(ctx, "corr-67890")

// Logger will automatically include these IDs
logger.WithRequestID(ctx).Info("Processing request")

Custom Fields

// Add custom fields to logger
logger.WithFields(map[string]interface{}{
    "user_id": "123",
    "action":  "create_post",
}).Info("User action performed")

// Chain multiple context additions
logger.WithRequestID(ctx).
    WithCorrelationID("corr-123").
    WithComponent("user-service").
    Info("Service operation completed")

Configuration

The logging system is configured through the LoggingConfig struct:

logging:
  level: "info"    # debug, info, warn, error
  format: "json"   # json, text

Environment variables can override configuration:

• GRAPHQL_SERVICE_LOGGING_LEVEL
• GRAPHQL_SERVICE_LOGGING_FORMAT

Log Levels

• Debug: Detailed information for debugging
• Info: General information about application flow
• Warn: Warning messages for potentially harmful situations
• Error: Error messages for failures that don't stop the application

Best Practices

1. Use Layer-Specific Loggers: Each layer has specialized logging methods
2. Include Context: Always pass context for request tracing
3. Log at Appropriate Levels: Use debug for detailed info, error for failures
4. Include Relevant Fields: Add structured data to make logs searchable
5. Don't Log Sensitive Data: Avoid logging passwords, tokens, or PII

Request Flow Example

[INFO] interface: HTTP request received method=POST path=/query request_id=req-abc123
[INFO] application: Use case started use_case=CreateUser request_id=req-abc123
[DEBUG] infrastructure: Database query executed query="INSERT INTO users..." request_id=req-abc123
[INFO] domain: Domain entity created entity_type=User entity_id=user-456 request_id=req-abc123
[INFO] application: Use case completed use_case=CreateUser duration_ms=45 request_id=req-abc123
[INFO] interface: HTTP request processed status_code=200 duration_ms=50 request_id=req-abc123